Tech News

I always see this Google Gemini button up in the corner in Gmail. When you hover over it, it does this cool animation where the little four-pointed star spins and the outer shape morphs between a couple different shapes that are also spinning.

I challenged myself to recreate the button using the new CSS shape() function sprinkled with animation to get things pretty close. Let me walk you through it.

Drawing the Shapes

Breaking it down, we need five shapes in total:

1. Four-pointed star
2. Flower-ish thing (yes, that’s the technical term)
3. Cylinder-ish thing (also the correct technical term)
4. Rounded hexagon
5. Circle

I drew these shapes in a graphics editing program (I like Affinity Designer, but any app that lets you draw vector shapes should work), outputted them in SVG, and then used a tool, like Temani Afif’s generator, to translate the SVG paths the program generated to the CSS shape() syntax.

Now, before I exported the shapes from Affinity Designer, I made sure the flower, hexagon, circle, and cylinder all had the same number of anchor points. If they don’t have the same number, then the shapes will jump from one to the next and won’t do any morphing. So, let’s use a consistent number of anchor points in each shape — even the circle — and we can watch these shapes morph into each other.

I set twelve anchor points on each shape because that was the highest amount used (the hexagon had two points near each curved corner).

Something related (and possibly hard to solve, depending on your graphics program) is that some of my shapes were wildly contorted when animating between shapes. For example, many shapes became smaller and began spinning before morphing into the next shape, while others were much more seamless. I eventually figured out that the interpolation was matching each shape’s starting point and continued matching points as it followed the shape.

The result is that the matched points move between shapes, so if the starting point for one shape is on opposite side of the starting point of the second shape, a lot of movement is necessary to transition from one shape’s starting point to the next shape’s starting point.

CodePen Embed Fallback

Luckily, the circle was the only shape that gave me trouble, so I was able to spin it (with some trial and error) until its starting point more closely matched the other starting points.

Another issue I ran into was that the cylinder-ish shape had two individual straight lines in shape() with line commands rather than using the curve command. This prevented the animation from morphing into the next shape. It immediately snapped to the next image without animating the transition, skipping ahead to the next shape (both when going into the cylinder and coming out of it).

I went back into Affinity Designer and ever-so-slightly added curvature to the two lines, and then it morphed perfectly. I initially thought this was a shape() quirk, but the same thing happened when I attempted the animation with the path() function, suggesting it’s more an interpolation limitation than it is a shape() limitation.

Once I finished adding my shape() values, I defined a CSS variable for each shape. This makes the later uses of each shape() more readable, not to mention easier to maintain. With twelve lines per shape the code is stinkin’ long (technical term) so we’ve put it behind an accordion menu.

View Shape Code :root { --hexagon: shape( evenodd from 6.47% 67.001%, curve by 0% -34.002% with -1.1735% -7.7% / -1.1735% -26.302%, curve by 7.0415% -12.1965% with 0.7075% -4.641% / 3.3765% -9.2635%, curve by 29.447% -17.001% with 6.0815% -4.8665% / 22.192% -14.1675%, curve by 14.083% 0% with 4.3725% -1.708% / 9.7105% -1.708%, curve by 29.447% 17.001% with 7.255% 2.8335% / 23.3655% 12.1345%, curve by 7.0415% 12.1965% with 3.665% 2.933% / 6.334% 7.5555%, curve by 0% 34.002% with 1.1735% 7.7% / 1.1735% 26.302%, curve by -7.0415% 12.1965% with -0.7075% 4.641% / -3.3765% 9.2635%, curve by -29.447% 17.001% with -6.0815% 4.8665% / -22.192% 14.1675%, curve by -14.083% 0% with -4.3725% 1.708% / -9.7105% 1.708%, curve by -29.447% -17.001% with -7.255% -2.8335% / -23.3655% -12.1345%, curve by -7.0415% -12.1965% with -3.665% -2.933% / -6.334% -7.5555%, close ); --flower: shape( evenodd from 17.9665% 82.0335%, curve by -12.349% -32.0335% with -13.239% -5.129% / -18.021% -15.402%, curve by -0.0275% -22.203% with -3.1825% -9.331% / -3.074% -16.6605%, curve by 12.3765% -9.8305% with 2.3835% -4.3365% / 6.565% -7.579%, curve by 32.0335% -12.349% with 5.129% -13.239% / 15.402% -18.021%, curve by 20.4535% -0.8665% with 8.3805% -2.858% / 15.1465% -3.062%, curve by 11.58% 13.2155% with 5.225% 2.161% / 9.0355% 6.6475%, curve by 12.349% 32.0335% with 13.239% 5.129% / 18.021% 15.402%, curve by 0.5715% 21.1275% with 2.9805% 8.7395% / 3.0745% 15.723%, curve by -12.9205% 10.906% with -2.26% 4.88% / -6.638% 8.472%, curve by -32.0335% 12.349% with -5.129% 13.239% / -15.402% 18.021%, curve by -21.1215% 0.5745% with -8.736% 2.9795% / -15.718% 3.0745%, curve by -10.912% -12.9235% with -4.883% -2.2595% / -8.477% -6.6385%, close ); --cylinder: shape( evenodd from 10.5845% 59.7305%, curve by 0% -19.461% with -0.113% -1.7525% / -0.11% -18.14%, curve by 10.098% -26.213% with 0.837% -10.0375% / 3.821% -19.2625%, curve by 29.3175% -13.0215% with 7.2175% -7.992% / 17.682% -13.0215%, curve by 19.5845% 5.185% with 7.1265% 0% / 13.8135% 1.887%, curve by 9.8595% 7.9775% with 3.7065% 2.1185% / 7.035% 4.8195%, curve by 9.9715% 26.072% with 6.2015% 6.933% / 9.4345% 16.082%, curve by 0% 19.461% with 0.074% 1.384% / 0.0745% 17.7715%, curve by -13.0065% 29.1155% with -0.511% 11.5345% / -5.021% 21.933%, curve by -26.409% 10.119% with -6.991% 6.288% / -16.254% 10.119%, curve by -20.945% -5.9995% with -7.6935% 0% / -14.8755% -2.199%, curve by -8.713% -7.404% with -3.255% -2.0385% / -6.1905% -4.537%, curve by -9.7575% -25.831% with -6.074% -6.9035% / -9.1205% -15.963%, close ); --star: shape( evenodd from 50% 24.787%, curve by 7.143% 18.016% with 0% 0% / 2.9725% 13.814%, curve by 17.882% 7.197% with 4.171% 4.2025% / 17.882% 7.197%, curve by -17.882% 8.6765% with 0% 0% / -13.711% 4.474%, curve by -7.143% 16.5365% with -4.1705% 4.202% / -7.143% 16.5365%, curve by -8.6115% -16.5365% with 0% 0% / -4.441% -12.3345%, curve by -16.4135% -8.6765% with -4.171% -4.2025% / -16.4135% -8.6765%, curve by 16.4135% -7.197% with 0% 0% / 12.2425% -2.9945%, curve by 8.6115% -18.016% with 4.1705% -4.202% / 8.6115% -18.016%, close ); --circle: shape( evenodd from 13.482% 79.505%, curve by -7.1945% -12.47% with -1.4985% -1.8575% / -6.328% -10.225%, curve by 0.0985% -33.8965% with -4.1645% -10.7945% / -4.1685% -23.0235%, curve by 6.9955% -12.101% with 1.72% -4.3825% / 4.0845% -8.458%, curve by 30.125% -17.119% with 7.339% -9.1825% / 18.4775% -15.5135%, curve by 13.4165% 0.095% with 4.432% -0.6105% / 8.9505% -0.5855%, curve by 29.364% 16.9% with 11.6215% 1.77% / 22.102% 7.9015%, curve by 7.176% 12.4145% with 3.002% 3.7195% / 5.453% 7.968%, curve by -0.0475% 33.8925% with 4.168% 10.756% / 4.2305% 22.942%, curve by -7.1135% 12.2825% with -1.74% 4.4535% / -4.1455% 8.592%, curve by -29.404% 16.9075% with -7.202% 8.954% / -18.019% 15.137%, curve by -14.19% -0.018% with -4.6635% 0.7255% / -9.4575% 0.7205%, curve by -29.226% -16.8875% with -11.573% -1.8065% / -21.9955% -7.9235%, close ); }

If all that looks like gobbledygook to you, it largely does to me too (and I wrote the shape() Almanac entry). As I said above, I converted them from stuff I drew to shape()s with a tool. If you can recognize the shapes from the custom property names, then you’ll have all you need to know to keep following along.

Breaking Down the Animation

After staring at the Gmail animation for longer than I would like to admit, I was able to recognize six distinct phases:

First, on hover:

1. The four-pointed star spins to the right and changes color.
2. The fancy blue shape spreads out from underneath the star shape.
3. The fancy blue shape morphs into another shape while spinning.
4. The purplish color is wiped across the fancy blue shape.

Then, after hover:

5. The fancy blue shape contracts (basically the reverse of Phase 2).
6. The four-pointed star spins left and returns to its initial color (basically the reverse of Phase 1).

That’s the run sheet we’re working with! We’ll write the CSS for all that in a bit, but first I’d like to set up the HTML structure that we’re hooking into.

The HTML

I’ve always wanted to be one of those front-enders who make jaw-dropping art out of CSS, like illustrating the Sistine chapel ceiling with a single div (cue someone commenting with a CodePen doing just that). But, alas, I decided I needed two divs to accomplish this challenge, and I thank you for looking past my shame. To those of you who turned up your nose and stopped reading after that admission: I can safely call you a Flooplegerp and you’ll never know it.

(To those of you still with me, I don’t actually know what a Flooplegerp is. But I’m sure it’s bad.)

Because the animation needs to spread out the blue shape from underneath the star shape, they need to be two separate shapes. And we can’t shrink or clip the main element to do this because that would obscure the star.

So, yeah, that’s why I’m reaching for a second div: to handle the fancy shape and how it needs to move and interact with the star shape.

<div id="geminianimation"> <div></div> </div> The Basic CSS Styling

Each shape is essentially defined with the same box with the same dimensions and margin spacing.

#geminianimation { width: 200px; aspect-ratio: 1/1; margin: 50px auto; position: relative; }

We can clip the box to a particular shape using a pseudo-element. For example, let’s clip a star shape using the CSS variable (--star) we defined for it and set a background color on it:

#geminianimation { width: 200px; aspect-ratio: 1; margin: 50px auto; position: relative; &::before { content: ""; clip-path: var(--star); width: 100%; height: 100%; position: absolute; background-color: #494949; } } CodePen Embed Fallback

We can hook into the container’s child div and use it to establish the animation’s starting shape, which is the flower (clipped with our --flower variable):

#geminianimation div { width: 100%; height: 100%; clip-path: var(--flower); background: linear-gradient(135deg, #217bfe, #078efb, #ac87eb, #217bfe); }

What we get is a star shape stacked right on top of a flower shape. We’re almost done with our initial CSS, but in order to recreate the animated color wipes, we need a much larger surface that allows us to “change” colors by moving the background gradient’s position. Let’s move the gradient so that it is declared on a pseudo element instead of the child div, and size it up by 400% to give us additional breathing room.

#geminianimation div { width: 100%; height: 100%; clip-path: var(--flower); &::after { content: ""; background: linear-gradient(135deg, #217bfe, #078efb, #ac87eb, #217bfe); width: 400%; height: 400%; position: absolute; } }

Now we can clearly see how the shapes are positioned relative to each other:

CodePen Embed Fallback Animating Phases 1 and 6

Now, I’ll admit, in my own hubris, I’ve turned up my very own schnoz at the humble transition property because my thinking is typically, Transitions are great for getting started in animation and for quick things, but real animations are done with CSS keyframes. (Perhaps I, too, am a Flooplegerp.)

But now I see the error of my ways. I can write a set of keyframes that rotate the star 180 degrees, turn its color white(ish), and have it stay that way for as long as the element is hovered. What I can’t do is animate the star back to what it was when the element is un-hovered.

I can, however, do that with the transition property. To do this, we add transition: 1s ease-in-out; on the ::before, adding the new background color and rotating things on :hover over the #geminianimation container. This accounts for the first and sixth phases of the animation we outlined earlier.

#geminianimation { &::before { /* Existing styles */ transition: 1s ease-in-out; } &:hover { &::before { transform: rotate(180deg); background-color: #FAFBFE; } } } Animating Phases 2 and 5

We can do something similar for the second and fifth phases of the animation since they are mirror reflections of each other. Remember, in these phases, we’re spreading and contracting the fancy blue shape.

We can start by shrinking the inner div’s scale to zero initially, then expand it back to its original size (scale: 1) on :hover (again using transitions):

#geminianimation { div { scale: 0; transition: 1s ease-in-out; } &:hover { div { scale: 1; } } CodePen Embed Fallback Animating Phase 3

Now, we very well could tackle this with a transition like we did the last two sets, but we probably should not do it… that is, unless you want to weep bitter tears and curse the day you first heard of CSS… not that I know from personal experience or anything… ha ha… ha.

CSS keyframes are a better fit here because there are multiple states to animate between that would require defining and orchestrating several different transitions. Keyframes are more adept at tackling multi-step animations.

What we’re basically doing is animating between different shapes that we’ve already defined as CSS variables that clip the shapes. The browser will handle interpolating between the shapes, so all we need is to tell CSS which shape we want clipped at each phase (or “section”) of this set of keyframes:

@keyframes shapeshift { 0% { clip-path: var(--circle); } 25% { clip-path: var(--flower); } 50% { clip-path: var(--cylinder); } 75% { clip-path: var(--hexagon); } 100% { clip-path: var(--circle); } }

Yes, we could combine the first and last keyframes (0% and 100%) into a single step, but we’ll need them separated in a second because we also want to animate the rotation at the same time. We’ll set the initial rotation to 0turn and the final rotation 1turn so that it can keep spinning smoothly as long as the animation is continuing:

@keyframes shapeshift { 0% { clip-path: var(--circle); rotate: 0turn; } 25% { clip-path: var(--flower); } 50% { clip-path: var(--cylinder); } 75% { clip-path: var(--hexagon); } 100% { clip-path: var(--circle); rotate: 1turn; } }

Note: Yes, turn is indeed a CSS unit, albeit one that often goes overlooked.

We want the animation to be smooth as it interpolates between shapes. So, I’m setting the animation’s timing function with ease-in-out. Unfortunately, this will also slow down the rotation as it starts and ends. However, because we’re both beginning and ending with the circle shape, the fact that the rotation slows coming out of 0% and slows again as it heads into 100% is not noticeable — a circle looks like a circle no matter its rotation. If we were ending with a different shape, the easing would be visible and I would use two separate sets of keyframes — one for the shape-shift and one for the rotation — and call them both on the #geminianimation child div .

#geminianimation:hover { div { animation: shapeshift 5s ease-in-out infinite forwards; } } Animating Phase 4

That said, we still do need one more set of keyframes, specifically for changing the shape’s color. Remember how we set a linear gradient on the parent container’s ::after pseudo, then we also increased the pseudo’s width and height? Here’s that bit of code again:

#geminianimation div { width: 100%; height: 100%; clip-path: var(--flower); &::after { content: ""; background: linear-gradient(135deg, #217bfe, #078efb, #ac87eb, #217bfe); width: 400%; height: 400%; position: absolute; } }

The gradient is that large because we’re only showing part of it at a time. And that means we can translate the gradient’s position to move the gradient at certain keyframes. 400% can be nicely divided into quarters, so we can move the gradient by, say, three-quarters of its size. Since its parent, the #geminianimation div, is already spinning, we don’t need any fancy movements to make it feel like the color is coming from different directions. We just translate it linearly and the spin adds some variability to what direction the color wipe comes from.

@keyframes gradientMove { 0% { translate: 0 0; } 100% { translate: -75% -75%; } } One final refinement

Instead of using the flower as the default shape, let’s change it to circle. This smooths things out when the hover interaction causes the animation to stop and return to its initial position.

And there you have it:

CodePen Embed Fallback Wrapping up

We did it! Is this exactly how Google accomplished the same thing? Probably not. In all honesty, I never inspected the animation code because I wanted to approach it from a clean slate and figure out how I would do it purely in CSS.

That’s the fun thing about a challenge like this: there are different ways to accomplish the same thing (or something similar), and your way of doing it is likely to be different than mine. It’s fun to see a variety of approaches.

Which leads me to ask: How would you have approached the Gemini button animation? What considerations would you take into account that maybe I haven’t?

Recreating Gmail’s Google Gemini Animation originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

In her talk Reveal the Hidden Forces Driving User Behavior at Future Product Days, Sarah Thompson shared insights on how to leverage behavioral science to create more effective user experiences. Here's my notes from her talk:

• While AI technology evolves exponentially, the human brain has not had a meaningful update in approximately 40,000 years so we're still designing for the "caveman brain"
• This unchanging human element provides a stable foundation for design that doesn't change with every wave of technology
• Behavioral science matters more than ever because we now have tools that allow us to scale faster than ever
• All decisions are emotional because there is an system one (emotional) part of the brain that makes decisions first. This part of the brain lights up 10 seconds before a person is even aware they made a decision
• System 1 thinking is fast, automatic, and helped us survive through gut reactions. It still runs the show today but uses shortcuts and over 180 known cognitive biases to navigate complexity
• Every time someone makes a decision, the emotional brain instantly predicts whether there are more costs or gains to taking action. More costs? Don't do it. More gains? Move forward
• The emotional brain only cares about six intuitive categories of costs and gains: internal (mental, emotional, physical) and external (social, material, temporal)
• Mental: "Thinking is hard" We evolved to conserve mental effort - people drop off with too many choices, stick with defaults. Can the user understand what they need to do immediately?
• Social: "We are wired to belong" We evolved to treat social costs as life or death situations. Does this make users feel safe, seen, or part of a group? Or does it raise embarrassment or exclusion?
• Emotional: "Automatic triggers" Imagery and visuals are the fastest way to set emotional tone. What automatic trigger (positive or negative) might this design bring up for someone?
• Physical: "We're wired to conserve physical effort" Physical gains include tap-to-pay, facial recognition, wearable data collection. Can I remove real or perceived physical effort?
• Material: "Our brains evolved in scarcity" Scarcity tactics like "Bob booked this three minutes ago" drive immediate action. Are we asking people to give something up or are we giving them something in return?
• Temporal: "We crave immediate rewards" Any time people have to wait, we see drop off. Can we give immediate reward or make people feel like they're saving time?
• You can't escape the caveman brain, but you can design for it.

In his How to solve the right problem with AI presentation at Future Product Days, Dave Crawford shared insights on how to effectively integrate AI into established products without falling into common traps. Here are my notes from his talk:

• Many teams have been given the directive to "go add some AI" to their products. With AI as a technology, it's very easy to fall into the trap of having an AI hammer where every problem looks like an AI nail.
• We need to focus on using AI where it's going to give the most value to users. It's not what we can do with AI, it's what makes sense to do with AI.

AI Interaction Patterns

• People typically encounter AI through four main interaction types
• Discovery AI: Helps people find, connect, and learn information, often taking the place of search
• Analytical AI: Analyzes data to provide insights, such as detecting cancer from medical scans
• Generative AI: Creates content like images, text, video, and more
• Functional AI: Actually gets stuff done by performing actions directly or interacting with other services
• AI interaction patterns exist on a context spectrum from high user burden to low user burden
• Open Text-Box Chat: Users must provide all context (ChatGPT, Copilot) - high overhead for users
• Sidecar Experience: Has some context about what's happening in the rest of the app, but still requires context switching
• Embedded: Highly contextual AI that appears directly in the flow of user's work
• Background: Agents that perform tasks autonomously without direct user interaction

Principles for AI Product Development

• Think Simply: Make something that makes sense and provides clear value. Users need to know what to expect from your AI experience
• Think Contextually: Can you make the experience more relevant for people using available context? Customize experiences within the user's workflow
• Think Big: AI can do a lot, so start big and work backwards.
• Mine, Reason, Infer: Make use of the information people give you.
• Think Proactively: What kinds of things can you do for people before they ask?
• Think Responsibly: Consider environmental and cost impacts of using AI.
• We should focus on delivering value first over delightful experiences

Problems for AI to Solve

• Boring tasks that users find tedious
• Complex activities users currently offload to other services
• Long-winded processes that take too much time
• Frustrating experiences that cause user pain
• Repetitive tasks that could be automated
• Don't solve problems that are already well-solved with simpler solutions
• Not all AI needs to be a chat interface. Sometimes traditional UI is better than AI
• Users' tolerance and forgiveness of AI is really low. It takes around 8 months for a user to want to try an AI product again after a bad experience
• We're now trying to find the right problems to solve rather than finding the right solutions to problems. Build things that solve real problems, not just showcase AI capabilities

In her The AI Adoption Gap: Why Great Features Go Unused talk at Future Product Days in Copenhagen, Kate Moran shared insights on why users don't utilize AI features in digital products. Here's my notes from her talk:

• The best way to understand the people we're creating digital products for is to talk to them and watch them use our products.
• Most people are not looking for AI features nor are they expecting them. People are task-focused, they're just trying to get something done and move on.
• Top three reasons people don't use AI features: they have no reason to use it, they don't see it, they don't know how to use it.
• There are other issues like in enterprise use cases, trust. But these are the main ones.
• People don't care about the technology, they care about the outcome. AI-powered is not a value-add. Solving someone's problem is a value-add.
• Amazon introduced a shopping assistant that when tested, people really liked because the assistant has a lot of context: what you bought before, what you are looking at now, and more
• However, people could not find this feature and did not know how to use it. The button is labeled "Rufus" people don't associate this with something that helps them get answers about their shopping.
• Findability is how well you can locate something you are looking for. Discoverability is finding something you weren't looking for.
• In interfaces that people use a lot (are familiar with), they often miss new features especially when they are introduced with a single action among many others
• Designers are making basic mistakes that don't have anything to do with AI (naming, icons, presentation)
• People say conversational interfaces are the easiest to use but it's not true. Open text fields feel like search, so people treat them like smarter search instead of using the full capability of AI systems
• People have gotten used to using succinct keywords in text fields instead of providing lots of context to AI models that produce better outcomes
• Smaller-scope AI features like automatic summaries that require no user interaction perform well because they integrate seamlessly into existing workflows
• These adoption challenges are not exclusive to AI but apply to any new feature, As a result, all your existing design skills remain highly valuable for AI features.

In his talk The Future of Product Creators at Future Product Days in Copenhagen, Tobias Ahlin argued that divergent opinions and debate, not just raw capability, are the missing factors for achieving useful outcomes from AI systems. Here are my notes from his presentation:

• Many people are exposing a future vision where parallel agents creating products and features on demand.
• 2025 marked the year when agentic workflows became part of daily product development. AI agents quantifiably outperform humans on standardized tests: reading, writing, math, coding, and even specialized fields.
• Yet we face the 100 interns problem: managing agents that are individually smarter but "have no idea where they're going"

Limitations of Current Systems

• Fundamental reasoning gaps: AI models have fundamental reasoning gaps. For example, AI can calculate rock-paper-scissors odds while failing to understand it has a built-in disadvantage by going second.
• Fatal mistakes in real-world applications: suggesting toxic glue for pizza, recommending eating rocks for minerals.
• Performance plateau problem: Unlike humans who improve with sustained effort, AI agents plateau after initial success and cannot meaningfully progress even with more time
• Real-world vs. benchmark performance: Research from Monitor shows 63% of AI-generated code fails tests, with 0% working without human intervention

Social Nature of Reasoning

• True reasoning is fundamentally a social function, "optimized for debate and communication, not thinking in isolation"
• Court systems exemplify this: adversarial arguments sharpen and improve each other through conflict
• Individual biases can complement each other when structured through critical scrutiny systems
• Teams naturally create conflicting interests: designers want to do more, developers prefer efficiency, PMs balance scope.This tension drives better outcomes
• AI significantly outperforms humans in creativity tests. In a Cornell study, GPT-4 performed better than 90.6% of humans in idea generation, with AI ideas being seven times more likely to rank in the top 10%
• So the cost of generating ideas is moving towards zero but human capability remains capped by our ability to evaluate and synthesize those ideas

Future of AI Agents

• Current agents primarily help with production but future productivity requires and equal amount of effort in evaluation and synthesis.
• Institutionalized disconfirmation: creating systems where disagreement drives clarity, similar to scientific peer review
• Agents designed to disagree in loops: one agent produces code, another evaluates it, creating feedback systems that can overcome performance plateaus
• True reasoning will come from agents that are designed to disagree in loops rather than simple chain-of-thought approaches

CSS typed arithmetic is genuinely exciting! It opens the door to new kinds of layout composition and animation logic we could only hack before. The first time I published something that leaned on typed arithmetic was in this animation:

CodePen Embed Fallback

But before we dive into what is happening in there, let’s pause and get clear on what typed arithmetic actually is and why it matters for CSS.

Browser Support: The CSS feature discussed in this article, typed arithmetic, is on the cutting edge. As of the time of writing, browser support is very limited and experimental. To ensure all readers can understand the concepts, the examples throughout this article are accompanied by videos and images, demonstrating the results for those whose browsers do not yet support this functionality. Please check resources like MDN or Can I Use for the latest support status.

The Types

If you really want to get what a “type” is in CSS, think about TypeScript. Now forget about TypeScript. This is a CSS article, where semantics actually matter.

In CSS, a type describes the unit space a value lives in, and is called a data-type. Every CSS value belongs to a specific type, and each CSS property and function only accepts the data type (or types) it expects.

• Properties like opacity or scale use a plain <number> with no units.
• width, height, other box metrics, and many additional properties use <length> units like px, rem, cm, etc.
• Functions like rotate() or conic-gradient() use an <angle> with deg, rad, or turn.
• animation and transition use <time> for their duration in seconds (s) or milliseconds (ms).

Note: You can identify CSS data types in the specs, on MDN, and other official references by their angle brackets: <data-type>.

There are many more data types like <percentage>, <frequency>, and <resolution>, but the types mentioned above cover most of our daily use cases and are all we will need for our discussion today. The mathematical concept remains the same for (almost) all types.

I say “almost” all types for one reason: not every data type is calculable. For instance, types like <color>, <string>, or <image> cannot be used in mathematical operations. An expression like "foo" * red would be meaningless. So, when we discuss mathematics in general, and typed arithmetic in particular, it is crucial to use types that are inherently calculable, like <length>, <angle>, or <number>.

The Rules of Typed Arithmetic

Even when we use calculable data types, there are still limitations and important rules to keep in mind when performing mathematical operations on them.

Addition and Subtraction

Sadly, a mix-and-match approach doesn’t really work here. Expressions like calc(3em + 45deg) or calc(6s - 3px) will not produce a logical result. When adding or subtracting, you must stick to the same data type.

Of course, you can add and subtract different units within the same type, like calc(4em + 20px) or calc(300deg - 1rad).

Multiplication

With multiplication, you can only multiply by a plain <number> type. For example: calc(3px * 7), calc(10deg * 6), or calc(40ms * 4). The result will always adopt the type and unit of the first value, with the new value being the product of the multiplication.

But why can you only multiply by a number? If we tried something like calc(10px * 10px) and assumed it followed “regular” math, we would expect a result of 100px². However, there are no squared pixels in CSS, and certainly no square degrees (though that could be interesting…). Because such a result is invalid, CSS only permits multiplying typed values by unitless numbers.

Division

Here, too, mixing and matching incompatible types is not allowed, and you can divide by a number just as you can multiply a number. But what happens when you divide a type by the same type?

Hint: this is where things get interesting.

Again, if we were thinking in terms of regular math, we would expect the units to cancel each other out, leaving only the calculated value. For example, 90x / 6x = 15. In CSS, however, this isn’t the case. Sorry, it wasn’t the case.

Previously, an expression like calc(70px / 10px) would have been invalid. But starting with Safari 18.2 and Chrome 140 (and hopefully soon in all other browsers), this expression now returns a valid number, which winds up being 7 in this case. This is the major change that typed arithmetic enables.

Is that all?!

That little division? Is that the big thing I called “genuinely exciting”? Yes! Because this one little feature opens the door to a world of creative possibilities. Case in point: we can convert values from one data type to another and mathematically condition values of one type based on another, just like in the swirl example I demoed at the top.

So, to understand what is happening there, let’s look at a more simplified swirl:

CodePen Embed Fallback

I have a container<div> with 36 <i> elements in the markup that are arranged in a spiral with CSS. Each element has an angle relative to the center point, rotate(var(--angle)), and a distance from that center point, translateX(var(--distance)).

The angle calculation is quite direct. I take the index of each <i> element using sibling-index() and multiply it by 10deg. So, the first element with an index of 1 will be rotated by 10 degrees (1 * 10deg), the second by 20 degrees (2 * 10deg), the third by 30 degrees (3 * 10deg), and so on.

i { --angle: calc(sibling-index() * 10deg); }

As for the distance, I want it to be directly proportional to the angle. I first use typed arithmetic to divide the angle by 360 degrees: var(--angle) / 360deg.

This returns the angle’s value, but as a unitless number, which I can then use anywhere. In this case, I can multiply it by a <length> value (e.g. 180px) that determines the element’s distance from the center point.

i { --angle: calc(sibling-index() * 10deg); --distance: calc(var(--angle) / 360deg * 180px); }

This way, the ratio between the angle and the distance remains constant. Even if we set the angle of each element differently, or to a new value, the elements will still align on the same spiral.

The Importance of the Divisor’s Unit

It’s important to clarify that when using typed arithmetic this way, you get a unitless number, but its value is relative to the unit of the divisor.

In our simplified spiral, we divided the angle by 360deg. The resulting unitless number, therefore, represents the value in degrees. If we had divided by 1turn instead, the result would be completely different — even though 1turn is equivalent to 360deg, the resulting unitless number would represent the value in turns.

A clearer example can be seen with <length> values.

Let’s say we are working with a screen width of 1080px. If we divide the screen width (100vw) by 1px, we get the number of pixels that fit into the screen width, which is, of course, 1080.

calc(100vw / 1px) /* 1080 */

However, if we divide that same width by 1em (and assume a font size of 16px), we get the number of em units that fit across the screen.

calc(100vw / 1em) /* 67.5 */

The resulting number is unitless in both cases, but its meaning is entirely dependent on the unit of the value we divided by.

From Length to Angle

Of course, this conversion doesn’t have to be from a type <angle> to a type <length>. Here is an example that calculates an element’s angle based on the screen width (100vw), creating a new and unusual kind of responsiveness.

CodePen Embed Fallback

And get this: There are no media queries in here! it’s all happening in a single line of CSS doing the calculations.

To determine the angle, I first define the width range I want to work within. clamp(300px, 100vw, 700px) gives me a closed range of 400px, from 300px to 700px. I then subtract 700px from this range, which gives me a new range, from -400px to 0px.

Using typed arithmetic, I then divide this range by 400px, which gives me a normalized, unitless number between -1 and 0. And finally, I convert this number into an <angle> by multiplying it by -90deg.

Here’s what that looks like in CSS when we put it all together:

p { rotate: calc(((clamp(300px, 100vw, 700px) - 700px) / 400px) * -90deg); } From Length to Opacity

Of course, the resulting unitless number can be used as-is in any property that accepts a <number> data type, such as opacity. What if I want to determine the font’s opacity based on its size, making smaller fonts more opaque and therefore clearer? Is it possible? Absolutely.

CodePen Embed Fallback

In this example, I am setting a different font-size value for each <p> element using a --font-size custom property. and since the range of this variable is from 0.8rem to 2rem, I first subtract 0.8rem from it to create a new range of 0 to 1.2rem.

I could divide this range by 1.2rem to get a normalized, unitless value between 0 and 1. However, because I don’t want the text to become fully transparent, I divide it by twice that amount (2.4rem). This gives me a result between 0 and 0.5, which I then subtract from the maximum opacity of 1.

p { font-size: var(--font-size, 1rem); opacity: calc(1 - (var(--font-size, 1rem) - 0.8rem) / 2.4rem); }

Notice that I am displaying the font size in pixel units even though the size is defined in rem units. I simply use typed arithmetic to divide the font size by 1px, which gives me the size in pixels as a unitless value. I then inject this value into the content of the the paragraph’s ::after pseudo-element.

p::after { counter-reset: px calc(var(--font-size, 1rem) / 1px); content: counter(px) 'px'; } Dynamic Width Colors

Of course, the real beauty of using native CSS math functions, compared to other approaches, is that everything happens dynamically at runtime. Here, for example, is a small demo where I color the element’s background relative to its rendered width.

p { --hue: calc(100cqi / 1px); background-color: hsl(var(--hue, 0) 75% 25%); }

You can drag the bottom-right corner of the element to see how the color changes in real-time.

CodePen Embed Fallback

Here’s something neat about this demo: because the element’s default width is 50% of the screen width and the color is directly proportional to that width, it’s possible that the element will initially appear in completely different colors on different devices with different screens. Again, this is all happening without any media queries or JavaScript.

An Extreme Example: Chaining Conversions

OK, so we’ve established that typed arithmetic is cool and opens up new and exciting possibilities. Before we put a bow on this, I wanted to pit this concept against a more extreme example. I tried to imagine what would happen if we took a <length> type, converted it to a <number> type, then to an <angle> type, back to a <number> type, and, from there, back to a <length> type.

Phew!

I couldn’t find a real-world use case for such a chain, but I did wonder what would happen if we were to animate an element’s width and use that width to determine the height of something else. All the calculations might not be necessary (maybe?), but I think I found something that looks pretty cool.

CodePen Embed Fallback

In this demo, the animation is on the solid line along the bottom. The vertical position of the ball, i.e. its height, relative to the line, is proportional to the line’s width. So, as the line expands and contracts, so does the path of the bouncing ball.

To create the parabolic arc that the ball moves along, I take the element’s width (100cqi) and, using typed arithmetic, divide it by 300px to get a unitless number between 0 and 1. I multiply that by 180deg to get an angle that I use in a sin() function (Juan Diego has a great article on this), which returns another unitless number between 0 and 1, but with a parabolic distribution of values.

Finally, I multiply this number by -200px, which outputs the ball’s vertical position relative to the line.

.ball { --translateY: calc(sin(calc(100cqi / 300px) * 180deg) * -200px) ; translate: -50% var(--translateY, 0); }

And again, because the ball’s position is relative to the line’s width, the ball’s position will remain on the same arc, no matter how we define that width.

Wrapping Up: The Dawn of Computational CSS

The ability to divide one typed value by another to produce a unitless number might seem like no big deal; more like a minor footnote in the grand history of CSS.

But as we’ve seen, this single feature is a quiet revolution. It dismantles the long-standing walls between different CSS data types, transforming them from isolated silos into a connected, interoperable system. We’ve moved beyond simple calculations, and entered the era of true Computational CSS.

This isn’t just about finding new ways to style a button or animate a loading spinner. It represents a fundamental shift in our mental model. We are no longer merely declaring static styles, but rather defining dynamic, mathematical relationships between properties. The width of an element can now intrinsically know about its color, an angle can dictate a distance, and a font’s size can determine its own visibility.

This is CSS becoming self-aware, capable of creating complex behaviors and responsive designs that adapt with a precision and elegance that previously required JavaScript.

So, the next time you find yourself reaching for JavaScript to bridge a gap between two CSS properties, pause for a moment. Ask yourself if there’s a mathematical relationship you can define instead. You might be surprised at how far you can go with just a few lines of CSS.

The Future is Calculable

The examples in this article are just the first steps into a much larger world. What happens when we start mixing these techniques with scroll-driven animations, view transitions, and other modern CSS features? The potential for creating intricate data visualizations, generative art, and truly fluid user interfaces, all natively in CSS, is immense. We are being handed a new set of creative tools, and the instruction manual is still being written.

CSS Typed Arithmetic originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

I’m inclined to take a few notes on Eric Bailey’s grand post about the use of inclusive personas in user research. As someone who has been in roles that have both used and created user personas, there’s so much in here

What’s the big deal, right? We’re often taught and encouraged to think about users early in the design process. It’s user’ centric design, so let’s personify 3-4 of the people we think represent our target audiences so our work is aligned with their objectives and needs. My master’s program was big on that and went deep into different approaches, strategies, and templates for documenting that research.

And, yes, it is research. The idea, in theory, is that by understanding the motivations and needs of specific users (gosh, isn’t “users” an awkward term?), we can “design backwards” so that the end goal is aligned to actions that get them there.

Eric sees holes in that process, particularly when it comes to research centered around inclusiveness. Why is that? Very good reasons that I’m compiling here so I can reference it later. There’s a lot to take in, so you’d do yourself a solid by reading Eric’s post in full. Your takeaways may be different than mine.

Traditional vs. Inclusive user research

First off, I love how Eric distinguishes what we typically refer to as the general type of user personas, like the ones I made to generalize an audience, from inclusive user personas that are based on individual experiences.

Inclusive user research practices are different than a lot of traditional user research. While there is some high-level overlap in approach, know the majority of inclusive user research is more focused on the individual experience and less about more general trends of behavior.

So, right off the bat we have to reframe what we’re talking about. There’s blanket personas that are placeholders for abstracting what we think we know about specific groups of people versus individual people that represent specific experiences that impact usability and access to content.

A primary goal in inclusive user research is often to identify concrete barriers that prevent someone from accessing the content they want or need. While the techniques people use are varied, these barriers represent insurmountable obstacles that stymie a whole host of navigation techniques and approaches.

If you’re looking for patterns, trends, and customer insights, know that what you want is regular user testing. Here, know that the same motivating factors you’re looking to uncover also exist for disabled people. This is because they’re also, you know, people.

Assistive technology is not exclusive to disabilities

It’s so easy to assume that using assistive tools automatically means accommodating a disability or impairment, but that’s not always the case. Choice points from Eric:

• First is that assistive technology is a means, and not an end.
• Some disabled people use more than one form of assistive technology, both concurrently and switching them in and out as needed.
• Some disabled people don’t use assistive technology at all.
• Not everyone who uses assistive technology has also mastered it.
• Disproportionate attention placed on one kind of assistive technology at the expense of others.
• It’s entirely possible to have a solution that is technically compliant, yet unintuitive or near-impossible to use in the actual. 

I like to keep in mind that assistive technologies are for everyone. I often think about examples in the physical world where everyone benefits from an accessibility enhancement, such as cutting curbs in sidewalks (great for skateboarders!), taking elevators (you don’t have to climb stairs in some cases), and using TV subtitles (I often have to keep the volume low for sleeping kids).

That’s the inclusive part of this. Everyone benefits rather than a specific subset of people.

Different personas, different priorities

What happens when inclusive research is documented separately from general user research?

Another folly of inclusive personas is that they’re decoupled from regular personas. This means they’re easily dismissible as considerations.

[…]

Disability is diversity, and the plain and honest truth is that diversity is missing from your personas if disability conditions are not present in at least some of them. This, in turn, means your personas are misrepresentative of the people in the abstract you claim to serve.

In practice, that means:

[…] we also want to hold space for things that need direct accessibility support and remediation when this consideration of accessibility fails to happen. It’s all about approach.

An example of how to consider your approach is when adding drag and drop support to an experience. […] [W]e want to identify if drag and drop is even needed to achieve the outcome the organization needs.

Thinking of a slick new feature that will impress your users? Great! Let’s make sure it doesn’t step on the toes of other experiences in the process, because that’s antithetical to inclusiveness. I recognize this temptation in my own work, particularly if I land on a novel UI pattern that excites me. The excitement and tickle I get from a “clever” idea gives me a blind side to evaluating the overall effectiveness of it.

Radical participatory design

Gosh dang, why didn’t my schoolwork ever cover this! I had to spend a little time reading the Cambridge University Press article explaining radical participatopry design (RPD) that Eric linked up.

Therefore, we introduce the term RPD to differentiate and represent a type of PD that is participatory to the root or core: full inclusion as equal and full members of the research and design team. Unlike other uses of the term PD, RPD is not merely interaction, a method, a way of doing a method, nor a methodology. It is a meta-methodology, or a way of doing a methodology. 

Ah, a method for methodology! We’re talking about not only including community members into the internal design process, but make them equal stakeholders as well. They get the power to make decisions, something the article’s author describes as a form of decolonization.

Or, as Eric nicely describes it:

Existing power structures are flattened and more evenly distributed with this approach.

Bonus points for surfacing the model minority theory:

The term “model minority” describes a minority group that society regards as high-performing and successful, especially when compared to other groups. The narrative paints Asian American children as high-achieving prodigies, with fathers who practice medicine, science, or law and fierce mothers who force them to work harder than their classmates and hold them to standards of perfection.

It introduces exclusiveness in the quest to pursue inclusiveness — a stereotype within a stereotype.

Thinking bigger

Eric caps things off with a great compilation of actionable takeaways for avoiding the pitfalls of inclusive user personas:

• Letting go of control leads to better outcomes.
• Member checking: letting participants review, comment on, and correct the content you’ve created based on their input.
• Take time to scrutinize the functions of our roles and how our organizations compel us to undertake them in order to be successful within them.
• Organizations can turn inwards and consider the artifacts their existing design and research processes produce. They can then identify opportunities for participants to provide additional clarity and corrections along the way.

On inclusive personas and inclusive user research originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

Several weeks ago, I participated in Front End Study Hall. Front End Study Hall is an HTML and CSS focused meeting held on Zoom every two weeks. It is an opportunity to learn from one another as we share our common interest in these two building blocks of the Web. Some weeks, there is more focused discussion while other weeks are more open ended and members will ask questions or bring up topics of interest.

Joe, the moderator of the group, usually starts the discussion with something he has been thinking about. In this particular meeting, he asked us about Sass. He asked us if we used it, if we liked it, and then to share our experience with it. I had planned to answer the question but the conversation drifted into another topic before I had the chance to answer. I saw it as an opportunity to write and to share some of the things that I have been thinking about recently.

Beginnings

I started using Sass in March 2012. I had been hearing about it through different things I read. I believe I heard Chris Coyier talk about it on his then-new podcast, ShopTalk Show. I had been interested in redesigning my personal website and I thought it would be a great chance to learn Sass. I bought an e-book version of Pragmatic Guide to Sass and then put what I was learning into practice as I built a new version of my website. The book suggested using Compass to process my Sass into CSS. I chose to use SCSS syntax instead of indented syntax because SCSS was similar to plain CSS. I thought it was important to stay close to the CSS syntax because I might not always have the chance to use Sass, and I wanted to continue to build my CSS skills.

It was very easy to get up and running with Sass. I used a GUI tool called Scout to run Compass. After some frustration trying to update Ruby on my computer, Scout gave me an environment to get up and going quickly. I didn’t even have to use the command line. I just pressed “Play” to tell my computer to watch my files. Later I learned how to use Compass through the command line. I liked the simplicity of that tool and wish that at least one of today’s build tools incorporated that same simplicity.

I enjoyed using Sass out of the gate. I liked that I was able to create reusable variables in my code. I could set up colors and typography and have consistency across my code. I had not planned on using nesting much but after I tried it, I was hooked. I really liked that I could write less code and manage all the relationships with nesting. It was great to be able to nest a media query inside a selector and not have to hunt for it in another place in my code.

Fast-forward a bit…

After my successful first experience using Sass in a personal project, I decided to start using it in my professional work. And I encouraged my teammates to embrace it. One of the things I liked most about Sass was that you could use as little or as much as you liked. I was still writing CSS but now had the superpower that the different helper functions in Sass enabled.

I did not get as deep into Sass as I could have. I used the Sass @extend rule more in the beginning. There are a lot of features that I did not take advantage of, like placeholder selectors and for loops. I have never been one to rely much on shortcuts. I use very few of the shortcuts on my Mac. I have dabbled in things like Emmet but tend to quickly abandon them because I am just use to writing things out and have not developed the muscle memory of using shortcuts.

Is it time to un-Sass?

By my count, I have been using Sass for over 13 years. I chose Sass over Less.js because I thought it was a better direction to go at the time. And my bet paid off. That is one of the difficult things about working in the technical space. There are a lot of good tools but some end up rising to the top and others fall away. I have been pretty fortunate that most of the decisions I have made have gone the way that they have. All the agencies I have worked for have used Sass.

At the beginning of this year, I finally jumped into building a prototype for a personal project that I have been thinking about for years: my own memory keeper. One of the few things that I liked about Facebook was the Memories feature. I enjoyed visiting that page each day to remember what I had been doing on that specific day in years past. But I felt at times that Facebook was not giving me all of my memories. And my life doesn’t just happen on Facebook. I also wanted a way to view memories from other days besides just the current date.

As I started building my prototype, I wanted to keep it simple. I didn’t want to have to set up any build tools. I decided to write CSS without Sass.

Okay, so that was my intention. But I soon realized that that I was using nesting. I had been working on it a couple of days before I realized it.

But my code was working. That is when I realized that the native nesting in CSS works much the same nesting in Sass. I had followed the discussion about implementing nesting in native CSS. At one point, the syntax was going to be very different. To be honest, I lost track of where things had landed because I was continuing to use Sass. Native CSS nesting was not a big concern to me right then.

I was amazed when I realized that nesting works just the same way. And it was in that moment that I began to wonder:

Is this finally the time to un-Sass?

I want to give credit where credit is due. I’m borrowing the term “un-Sass” from Stu Robson, who is actually in the middle of writing a series called “Un-Sass’ing my CSS” as I started thinking about writing this post. I love the term “un-Sass” because it is easy to remember and so spot on to describe what I have been thinking about.

Here is what I am taking into consideration:

Custom Properties

I knew that a lot about what I liked about Sass had started to make its way into native CSS. Custom properties were one of the first things. Custom properties are more powerful than Sass variables because you can assign a new value to a custom property in a media query or in a theming system, like light and dark modes. That’s something Sass is unable to do since variables become static once they are compiled into vanilla CSS. You can also assign and update custom properties with JavaScript. Custom properties also work with inheritance and have a broader scope than Sass variables.

So, yeah. I found that not only was I already fairly familiar with the concept of variables, thanks to Sass, but the native CSS version was much more powerful.

I first used CSS Custom Properties when building two different themes (light and dark) for a client project. I also used them several times with JavaScript and liked how it gave me new possibilities for using CSS and JavaScript together. In my new job, we use custom properties extensively and I have completely switched over to using them in any new code that I write. I made use of custom properties extensively when I redesigned my personal site last year. I took advantage of it to create a light and dark theme and I utilized it with Utopia for typography and spacing utilities.

Nesting

When Sass introduced nesting, it simplified the writing of CSS code because you write style rules within another style rule (usually a parent). This means that you no longer had to write out the full descendent selector as a separate rule. You could also nest media queries, feature queries, and container queries.

This ability to group code together made it easier to see the relationships between parent and child selectors. It was also useful to have the media queries, container queries, or feature queries grouped inside those selectors rather than grouping all the media query rules together further down in the stylesheet.

I already mentioned that I stumbled across native CSS nesting when writing code for my memory keeper prototype. I was very excited that the specification extended what I already knew about nesting from Sass.

Two years ago, the nesting specification was going to require you to start the nested query with the & symbol, which was different from how it worked in Sass.

.footer { a { color: blue } } /* 2023 */ .footer { & a { color: blue } /* This was valid then */ }

But that changed sometime in the last two years and you no longer need the ampersand (&) symbol to write a nested query. You can write just as you had been writing it in Sass. I am very happy about this change because it means native CSS nesting is just like I have been writing it in Sass.

/* 2025 */ .footer { a { color: blue } /* Today's valid syntax */ }

There are some differences in the native implementation of nesting versus Sass. One difference is that you cannot create concatenated selectors with CSS. If you love BEM, then you probably made use of this feature in Sass. But it does not work in native CSS.

.card { &__title {} &__body {} &__footer {} }

It does not work because the & symbol is a live object in native CSS and it is always treated as a separate selector. Don’t worry, if you don’t understand that, neither do I. The important thing is to understand the implication – you cannot concatenate selectors in native CSS nesting.

If you are interested in reading a bit more about this, I would suggest Kevin Powell’s, “Native CSS Nesting vs. Sass Nesting” from 2023. Just know that the information about having to use the & symbol before an element selector in native CSS nesting is out of date.

I never took advantage of concatenated selectors in my Sass code so this will not have an impact on my work. For me, nesting is native CSS is equivalent to how I was using it in Sass and is one of the reasons why to consider un-Sassing.

My advice is to be careful with nesting. I would suggest trying to keep your nested code to three levels at the most. Otherwise, you end up with very long selectors that may be more difficult to override in other places in our codebase. Keep it simple.

The color-mix() function

I liked using the Sass color module to lighten or darken a color. I would use this most often with buttons where I wanted the hover color to be different. It was really easy to do with Sass. (I am using $color to stand in for the color value).

background-color: darken($color, 20%);

The color-mix() function in native CSS allows me to do the same thing and I have used it extensively in the past few months since learning about it from Chris Ferdinandi.

background-color: color-mix(in oklab, var(--color), #000000 20%); Mixins and functions

I know that a lot of developers who use Sass make extensive use of mixins. In the past, I used a fair number of mixins. But a lot of the time, I was just pasting mixins from previous projects. And many times, I didn’t make as much use of them as I could because I would just plain forget that I had them. They were always nice helper functions and allowed me to not have to remember things like clearfix or font smoothing. But those were also techniques that I found myself using less and less.

I also utilized functions in Sass and created several of my own, mostly to do some math on the fly. I mainly used them to convert pixels into ems because I liked being able to define my typography and spacing as relative and creating relationships in my code. I also had written a function to covert pixels to ems for custom media queries that did not fit within the breakpoints I normally used. I had learned that it was a much better practice to use ems in media queries so that layouts would not break when a user used page zoom.

Currently, we do not have a way to do mixins and functions in native CSS. But there is work being done to add that functionality. Geoff wrote about the CSS Functions and Mixins Module.

I did a little experiment for the use case I was using Sass functions for. I wanted to calculate em units from pixels in a custom media query. My standard practice is to set the body text size to 100% which equals 16 pixels by default. So, I wrote a calc() function to see if I could replicate what my Sass function provided me.

@media (min-width: calc((600 / 16) * 1em));

This custom media query is for a minimum width of 600px. This would work based on my setting the base font size to 100%. It could be modified.

Tired of tooling

Another reason to consider un-Sassing is that I am simply tired of tooling. Tooling has gotten more and more complex over the years, and not necessarily with a better developer experience. From what I have observed, today’s tooling is predominantly geared towards JavaScript-first developers, or anyone using a framework like React. All I need is a tool that is easy to set up and maintain. I don’t want to have to learn a complex system in order to do very simple tasks.

Another issue is dependencies. At my current job, I needed to add some new content and styles to an older WordPress site that had not been updated in several years. The site used Sass, and after a bit of digging, I discovered that the previous developer had used CodeKit to process the code. I renewed my Codekit license so that I could add CSS to style the content I was adding. It took me a bit to get the settings correct because the settings in the repo were not saving the processed files to the correct location.

Once I finally got that set, I continued to encounter errors. Dart Sass, the engine that powers Sass, introduced changes to the syntax that broke the existing code. I started refactoring a large amount of code to update the site to the correct syntax, allowing me to write new code that would be processed. 

I spent about 10 minutes attempting to refactor the older code, but was still getting errors. I just needed to add a few lines of CSS to style the new content I was adding to the site. So, I decided to go rogue and write the new CSS I needed directly in the WordPress template. I have had similar experiences with other legacy codebases, and that’s the sort of thing that can happen when you’re super reliant on third-party dependencies. You spend more time trying to refactor the Sass code so you can get to the point where you can add new code and have it compiled.

All of this has left me tired of tooling. I am fortune enough at my new position that the tooling is all set up through the Django CMS. But even with that system, I have run into issues. For example, I tried using a mixture of percentage and pixels values in a minmax() function and Sass was trying to evaluate it as a math function and the units were incompatible.

grid-template-columns: repeat(auto-fill, minmax(min(200px, 100%), 1fr));

I needed to be able to escape and not have Sass try to evaluate the code as a math function:

grid-template-columns: repeat(auto-fill, minmax(unquote("min(200px, 100%)"), 1fr));

This is not a huge pain point but it was something that I had to take some time to investigate that I could have been using to write HTML or CSS. Thankfully, that is something Ana Tudor has written about.

All of these different pain points lead me to be tired of having to mess with tooling. It is another reason why I have considered un-Sassing.

Verdict

So what is my verdict — is it time to un-Sass?

Please don’t hate me, but my conclusion is: it depends. Maybe not the definitive answer you were looking for.

But you probably are not surprised. If you have been working in web development even a short amount of time, you know that there are very few definitive ways of doing things. There are a lot of different approaches, and just because someone else solves it differently, does not mean you are right and they are wrong (or vice versa). Most things come down to the project you are working on, your audience, and a host of other factors.

For my personal site, yes, I would like to un-Sass. I want to kick the build process to the curb and eliminate those dependencies. I would also like for other developers to be able to view source on my CSS. You can’t view source on Sass. And part of the reason I write on my site is to share solutions that might benefit others, and making code more accessible is a nice maintenance enhancement.

My personal site does not have a very large codebase. I could probably easily un-Sass it in a couple of days or over a weekend.

But for larger sites, like the codebase I work with at my job. I wouldn’t suggest un-Sassing it. There is way too much code that would have to be refactored and I am unable to justify the cost for that kind of effort. And honestly, it is not something I feel motivated to tackle. It works just fine the way that it is. And Sass is still a very good tool to use. It’s not “breaking” anything.

Your project may be different and there might be more gains from un-Sassing than the project I work on. Again, it depends.

The way forward

It is an exciting time to be a CSS developer. The language is continuing to evolve and mature. And every day, it is incorporating new features that first came to us through other third-party tools such as Sass. It is always a good idea to stop and re-evaluate your technology decisions to determine if they still hold up or if more modern approaches would be a better way forward.

That does not mean we have to go back and “fix” all of our old projects. And it might not mean doing a complete overhaul. A lot of newer techniques can live side by side with the older ones. We have a mix of both Sass variables and CSS custom properties in our codebase. They don’t work against each other. The great thing about web technologies is that they build on each other and there is usually backward compatibility.

Don’t be afraid to try new things. And don’t judge your past work based on what you know today. You did the best you could given your skill level, the constraints of the project, and the technologies you had available. You can start to incorporate newer ways right alongside the old ones. Just build websites!

Is it Time to Un-Sass? originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

With each new technology platform shift, what defines a software application changes dramatically. Even though we're still in the midst of the AI shift, there's emergent properties that seem to be shaping what at least a subset of AI applications, let's call them chat apps, might look like going forward.

At a high level, applications are defined by the systems they're discovered and operated in. This frames what capabilities they can utilize, their primary inputs, outputs, and more. That sounds abstract so let's make it concrete. Applications during the PC era were compiled binaries sold as shrink-wrapped software that used local compute and storage, monitors as output, and the mouse and keyboard as input.

These capabilities defined not only their interfaces (GUI) but their abilities as well. The same is true for applications born of the AI era. How they're discovered and where they operate will also define them. And that's particularly true of "chat apps".

So what's a chat app? Most importantly a chat app's compute engine is an AI model which means all the capabilities of the model also become capabilities of the app. If the model can translate from one language to another, the app can. If a model can generate PDF files, the app can. It's worth noting that "model" could be a combination of AI models (with routing), prompts and tools. But to an end user, it would appear as a singular entity like ChatGPT or Claude.

When an application runs in Claude or ChatGPT, it's like running in an OS (windows during the PC era, iOS during the mobile era). So how do you run a chat app in an AI model like Claude and what happens when you do? Today an application can be added to Claude as a "connector" probably running as a remote Model Context Protocol (MCP) server. The process involves some clicking through forms and dialog boxes but once setup, Claude has the ability to use the application on behalf of the person that added it.

As mentioned above, the capabilities of Claude are now the capabilities of the app. Claude can accept natural language as input, so can the app. When people upload an image to Claude, it understands its content, so does the app. Claude can search and browse the Web, so can the app. The same is true for output. If Claude can turn information into a PDF, so can the app. If Claude can add information to Salesforce, so can the app. You get the idea.

So what's left for the application to do? If the AI model provides input, output, and processing capabilities, what does a chat app do? In it's simplest form a chat app can be a database that stores the information the app uses for input, output, and processing and a set of dynamic instructions for the AI model on how to use it.

As always, a tangible example makes this clear. Let's say I want to make a chat app for tracking the concerts I'm attending. Using a service like AgentDB, I can start with an existing file of concerts I'm tracking or ask a model to create one. I then have a remote MCP server backed by a database of concert information and a dynamic template that continually instructs an AI model on to use it.

When I add that remote MCP link to Claude, I can: upload screenshots of upcoming concerts to track using Claude's image parsing ability); generate a calendar view of all my concerts (using Claude's coding ability); find additional information about an upcoming show (using Claude's Web search tools); and so on. All of these capabilities of the Claude "model" work with my database plus template, aka my chat app.

You can make your own chat apps instantly by using AgentDB to create a remote MCP link and adding it to Claude as a connector. It's not a very intuitive process today but will very likely feel as simple as using a mobile app store in the not too distant future. At which point, chat apps will probably proliferate.

When I first started messing around with code, rounded corners required five background images or an image sprite likely created in Photoshop, so when border-radius came onto the scene, I remember everybody thinking that it was the best thing ever. Web designs were very square at the time, so to have border-radius was super cool, and it saved us a lot of time, too.

Chris’ border-radius article from 2009, which at the time of writing is 16 years old (wait, how old am I?!), includes vendor prefixes for older web browsers, including “old Konqueror browsers” (-khtml-border-radius). What a time to be alive!

We’re much less excited about rounded corners nowadays. In fact, sharp corners have made a comeback and are just as popular now, as are squircles (square-ish circles or circle-y squares, take your pick), which is exactly what the corner-shape CSS property enables us to create (in addition to many other cool UI effects that I’ll be walking you through today).

At the time of writing, only Chrome 139 and above supports corner-shape, which must be used with the border-radius property or/and any of the related individual properties (i.e., border-top-left-radius, border-top-right-radius, border-bottom-right-radius, and border-bottom-left-radius):

CodePen Embed Fallback Snipped corners using corner-shape: bevel

These snipped corners are becoming more and more popular as UI designers embrace brutalist aesthetics.

In the example above, it’s as easy as using corner-shape: bevel for the snipped corners effect and then border-bottom-right-radius: 16px for the size.

corner-shape: bevel; border-bottom-right-radius: 16px;

We can do the same thing and it really works with a cyberpunk aesthetic:

CodePen Embed Fallback Slanted sections using corner-shape: bevel

Slanted sections is a visual effect that’s even more popular, probably not going anywhere, and again, helps elements to look a lot less like the boxes that they are.

Before we dive in though, it’s important to keep in mind that each border radii has two semi-major axes, a horizontal axis and a vertical axis, with a ‘point’ (to use vector terminology) on each axis. In the example above, both are set to 16px, so both points move along their respective axis by that amount, away from their corner of course, and then the beveled line is drawn between them. In the slanted section example below, however, we need to supply a different point value for each axis, like this:

corner-shape: bevel; border-bottom-right-radius: 100% 50px; CodePen Embed Fallback

The first point moves along 100% of the horizontal axis whereas the second point travels 50px of the vertical axis, and then the beveled line is drawn between them, creating the slant that you see above.

By the way, having different values for each axis and border radius is exactly how those cool border radius blobs are made.

Sale tags using corner-shape: round bevel bevel round

You’ve see those sale tags on almost every e-commerce website, either as images or with rounded corners and not the pointy part (other techniques just aren’t worth the trouble). But now we can carve out the proper shape using two different types of corner-shape at once, as well as a whole set of border radius values:

CodePen Embed Fallback

You’ll need corner-shape: round bevel bevel round to start off. The order flows clockwise, starting from the top-left, as follows:

• top-left
• top-right
• bottom-right
• bottom-left

Just like with border-radius. You can omit some values, causing them to be inferred from other values, but both the inference logic and resulting value syntax lack clarity, so I’d just avoid this, especially since we’re about to explore a more complex border-radius:

corner-shape: round bevel bevel round; border-radius: 16px 48px 48px 16px / 16px 50% 50% 16px;

Left of the forward slash (/) we have the horizontal-axis values of each corner in the order mentioned above, and on the right of the /, the vertical-axis values. So, to be clear, the first and fifth values correspond to the same corner, as do the second and sixth, and so on. You can unpack the shorthand if it’s easier to read:

border-top-left-radius: 16px; border-top-right-radius: 48px 50%; border-bottom-right-radius: 48px 50%; border-bottom-left-radius: 16px;

Up until now, we’ve not really needed to fully understand the border radius syntax. But now that we have corner-shape, it’s definitely worth doing so.

As for the actual values, 16px corresponds to the round corners (this one’s easy to understand) while the 48px 50% values are for the bevel ones, meaning that the corners are ‘drawn’ from 48px horizontally to 50% vertically, which is why and how they head into a point.

Regarding borders — yes, the pointy parts would look nicer if they were slightly rounded, but using borders and outlines on these elements yields unpredictable (but I suspect intended) results due to how browsers draw the corners, which sucks.

Arrow crumbs using the same method

Yep, same thing.

CodePen Embed Fallback

We essentially have a grid row with negative margins, but because we can’t create ‘inset’ arrows or use borders/outlines, we have to create an effect where the fake borders of certain arrows bleed into the next. This is done by nesting the exact same shape in the arrows and then applying something to the effect of padding-right: 3px, where 3px is the value of the would-be border. The code comments below should explain it in more detail (the complete code in the Pen is quite interesting, though):

<nav> <ol> <li> <a>Step 1</a> </li> <li> <a>Step 2</a> </li> <li> <a>Step 3</a> </li> </ol> </nav> ol { /* Clip n’ round */ overflow: clip; border-radius: 16px; li { /* Arrow color */ background: hsl(270 100% 30%); /* Reverses the z-indexes, making the arrows stack */ /* Result: 2, 1, 0, ... (sibling-x requires Chrome 138+) */ z-index: calc((sibling-index() * -1) + sibling-count()); &:not(:last-child) { /* Arrow width */ padding-right: 3px; /* Arrow shape */ corner-shape: bevel; border-radius: 0 32px 32px 0 / 0 50% 50% 0; /* Pull the next one into this one */ margin-right: -32px; } a { /* Same shape */ corner-shape: inherit; border-radius: inherit; /* Overlay background */ background: hsl(270 100% 50%); } } } Tooltips using corner-shape: scoop CodePen Embed Fallback

To create this tooltip style, I’ve used a popover, anchor positioning (to position the caret relative to the tooltip), and corner-shape: scoop. The caret shape is the same as the arrow shape used in the examples above, so feel free to switch scoop to bevel if you prefer the classic triangle tooltips.

A quick walkthrough:

<!-- Connect button to tooltip --> <button popovertarget="tooltip" id="button">Click for tip</button> <!-- Anchor tooltip to button --> <div anchor="button" id="tooltip" popover>Don’t eat yellow snow</div> #tooltip { /* Define anchor */ anchor-name: --tooltip; /* Necessary reset */ margin: 0; /* Center vertically */ align-self: anchor-center; /* Pin to right side + 15 */ left: calc(anchor(right) + 15px); &::after { /* Create caret */ content: ""; width: 5px; height: 10px; corner-shape: scoop; border-top-left-radius: 100% 50%; border-bottom-left-radius: 100% 50%; /* Anchor to tooltip */ position-anchor: --tooltip; /* Center vertically */ align-self: anchor-center; /* Pin to left side */ right: anchor(left); /* Popovers have this already (required otherwise) */ position: fixed; } }

If you’d rather these were hover-triggered, the upcoming Interest Invoker API is what you’re looking for.

Realistic highlighting using corner-shape: squircle bevel

The <mark> element, used for semantic highlighting, defaults with a yellow background, but it doesn’t exactly create a highlighter effect. By adding the following two lines of CSS, which admittedly I discovered by experimenting with completely random values, we can make it look more like a hand-waved highlight:

mark { /* A...squevel? */ corner-shape: squircle bevel; border-radius: 50% / 1.1rem 0.5rem 0.9rem 0.7rem; /* Prevents background-break when wrapping */ box-decoration-break: clone; } CodePen Embed Fallback

We can also use squircle by itself to create those fancy-rounded app icons, or use them on buttons/cards/form controls/etc. if you think the ‘old’ border radius is starting to look a bit stale:

CodePen Embed Fallback CodePen Embed Fallback Hand-drawn boxes using the same method

Same thing, only larger. Kind of looks like a hand-drawn box?

CodePen Embed Fallback

Admittedly, this effect doesn’t look as awesome on a larger scale, so if you’re really looking to wow and create something more akin to the Red Dead Redemption aesthetic, this border-image approach would be better.

Clip a background with corner-shape: notch

Notched border radii are ugly and I won’t hear otherwise. I don’t think you’ll want to use them to create a visual effect, but I’ve learned that they’re useful for background clipping if you set the irrelevant axis to 50% and the axis of the side that you want to clip by the amount that you want to clip it by. So if you wanted to clip 30px off the background from the left for example, you’d choose 30px for the horizontal axes and 50% for the vertical axes (for the -left-radius properties only, of course).

corner-shape: notch; border-top-left-radius: 30px 50%; border-bottom-left-radius: 30px 50%; CodePen Embed Fallback Conclusion

So, corner-shape is actually a helluva lot of fun. It certainly has more uses than I expected, and no doubt with some experimentation you’ll come up with some more. With that in mind, I’ll leave it to you CSS-Tricksters to mess around with (remember though, you’ll need to be using Chrome 139 or higher).

As a parting gift, I leave you with this very cool but completely useless CSS Tie Fighter, made with corner-shape and anchor positioning:

CodePen Embed Fallback

What Can We Actually Do With corner-shape? originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

Every time I present on AI product design, I'm asked about AI and intellectual property. Specifically: aren't you worried about AI models "stealing" your work? I always answer that if I accused AI models of theft, I'd have to accuse myself as well. Let me explain…

I've spent 30 years writing three books and over two thousand articles on digital product design and strategy. But during those same 30 years? I've consumed exponentially more. Countless books, articles, tweets. Thousands of conversations. Products I've used, solutions I've analyzed. All of it shaped what I know and how I write.

If you asked me to trace the next sentence I type back to its sources, to properly attribute the influences that led to those specific words, I couldn't do it. The synthesis happens at a level I can't fully decompose.

AI models are doing what we do. Reading, viewing, learning, synthesizing. The only difference is scale. They process vastly more information than any human could. When they generate text, they're drawing from that accumulated knowledge. Sound familiar?

So when an AI model produces something influenced by my writings, how is that different from a designer who read my book and applies those principles? I put my books out there for people to buy and learn from. My articles? Free for anyone to read. Why should machines be excluded from that learning opportunity?

"But won't AI companies unfairly profit from training on your content?"

From AI model companies, for $20 per month, I get an assistant that's read more than I ever could, available instantly, capable of helping with everything from code reviews to strategic analysis. That same $20 couldn't buy me two hours of entry-level human assistance.

The benefit I receive from these models, trained on the collective knowledge of millions of contributors, including my microscopic contribution, dwarfs any hypothetical loss from my content being training data. In fact, I'm humbled that my thoughts could even be part of a knowledge base used by billions of people.

So let machines learn, just like humans do. For me, the value I get back from well-trained AI models far exceeds what my contribution puts in.

Stu Robson is on a mission to “un-Sass” his CSS. I see articles like this pop up every year, and for good reason as CSS has grown so many new legs in recent years. So much so that much of the core features that may have prompted you to reach for Sass in the past are now baked directly into CSS. In fact, we have Jeff Bridgforth on tap with a related article next week.

What I like about Stu’s stab at this is that it’s an ongoing journey rather than a wholesale switch. In fact, he’s out with a new post that pokes specifically at compiling multiple CSS files into a single file. Splitting and organizing styles into separate files is definitely the reason I continue to Sass-ify my work. I love being able to find exactly what I need in a specific file and updating it without having to dig through a monolith of style rules.

But is that a real reason to keep using Sass? I’ve honestly never questioned it, perhaps due to a lizard brain that doesn’t care as long as something continues to work. Oh, I want partialized style files? Always done that with a Sass-y toolchain that hasn’t let me down yet. I know, not the most proactive path.

Stu outlines two ways to compile multiple CSS files when you aren’t relying on Sass for it:

Using PostCSS

Ah, that’s right, we can use PostCSS both with and without Sass. It’s easy to forget that PostCSS and Sass are compatible, but not dependent on one another.

postcss main.css -o output.css

Stu explains why this could be a nice way to toe-dip into un-Sass’ing your work:

PostCSS can seamlessly integrate with popular build tools like webpack, Gulp, and Rollup, allowing you to incorporate CSS compilation into your existing development workflow without potential, additional configuration headaches.

Custom Script for Compilation

The ultimate thing would be eliminating the need for any dependencies. Stu has a custom Node.js script for that:

const fs = require('fs'); const path = require('path'); // Function to read and compile CSS function compileCSS(inputFile, outputFile) { const cssContent = fs.readFileSync(inputFile, 'utf-8'); const imports = cssContent.match(/@import\s+['"]([^'"]+)['"]/g) || []; let compiledCSS = ''; // Read and append each imported CSS file imports.forEach(importStatement => { const filePath = importStatement.match(/['"]([^'"]+)['"]/)[1]; const fullPath = path.resolve(path.dirname(inputFile), filePath); compiledCSS += fs.readFileSync(fullPath, 'utf-8') + '\n'; }); // Write the compiled CSS to the output file fs.writeFileSync(outputFile, compiledCSS.trim()); console.log(`Compiled CSS written to ${outputFile}`); } // Usage const inputCSSFile = 'index.css'; // Your main CSS file const outputCSSFile = 'output.css'; // Output file compileCSS(inputCSSFile, outputCSSFile);

Not 100% free of dependencies, but geez, what a nice way to reduce the overhead and still combine files:

node compile-css.js

This approach is designed for a flat file directory. If you’re like me and prefer nested subfolders:

With the flat file structure and single-level import strategy I employ, nested imports (you can do with postcss-import aren’t necessary for my project setup, simplifying the compilation process while maintaining clean organisation.

Very cool, thanks Stu! And check out the full post because there’s a lot of helpful context behind this, particularly with the custom script.

Compiling Multiple CSS Files into One originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

That’s what Donnie D’Amato asks in a recent post:

You are asked to build a website but you can use only 4 CSS properties, what are those?

This really got the CSS-Tricks team talking. It’s the nerdy version of “if you could only take one album with you on a remote island…” And everyone had a different opinion which is great because it demonstrates the messy, non-linear craft that is thinking like a front-end developer.

Seems like a pretty straightforward thing to answer, right? But like Donnie says, this takes some strategy. Like, say spacing is high on your priority list. Are you going to use margin? padding? Perhaps you’re leaning into layout and go with gap as part of a flexbox direction… but then you’re committing to display as one of your options. That can quickly eat up your choices!

Our answers are pretty consistent, but converged even more as the discussion wore on and all of us were coming at it with different priorities. I’ll share each person’s “gut” reaction because I like how raw it is. I think you’ll see that there’s always a compromise in the mix, but those compromises really reveal a person’s cards as far as what they think is most important in a situation with overly tight constraints.

Juan Diego Rodriguez

Juan and I came out pretty close to the same choices, as we’ll see in a bit:

• font: Typography is a priority and we get a lot of constituent properties with this single shorthand.
• padding: A little padding makes things breath and helps with visual separation.
• background: Another shorthand with lots of styling possibilities in a tiny package.
• color: More visual hierarchy.

But he was debating with himself a bit in the process:

Thinking about switching color with place-items, since it works in block elements. grid would need display, though).

Ryan Trimble

Ryan’s all about that bass structure:

• display: This opens up a world of layouts, but most importantly flex.
• flex-direction: It’s a good idea to consider multi-directional layouts that are easily adjustable with media queries.
• width: This helps constrain elements and text, as well as divide up flex containers.
• margin: This is for spacing that’s bit more versatile than gap, while also allowing us to center elements easily.

And Ryan couldn’t resist reaching a little out of bounds:

For automatic color theme support, and no extra CSS properties required: <meta name="color-scheme" content="dark light"> 

Danny Schwarz

Every team needs a wild card:

On the contrary I think I’d choose font, padding, and color. I wouldn’t even choose a 4th.

• font: This isn’t a big surprise if you’re familiar with Danny’s writing.
• padding: So far, Ryan’s the only one to eschew padding as a core choice!
• color: Too bad this isn’t baked right into font!

I’ll also point out that Danny soon questioned his decision to use all four choices:

I supposed we’d need width to achieve a good line length.

Sunkanmi Fafowora

This is the first list to lean squarely into CSS Grid, allowing the grid shorthand to take up a choice in favor of having a complete layout system:

• font: This is a popular one, right?
• display: Makes grid available
• grid: Required for this display approach
• color: For sprinkling in text color where it might help

I love that Ryan and Sunkanmi are thinking in terms of structure, albeit in very different ways for different reasons!

Zell Liew

In Zell’s own words: “Really really plain and simple site here.”

• font: Content is still the most important piece of information.
• max-width: Ensures type measure is ok.
• margin: Lets me play around with spacing.
• color: This ensures there’s no pure black/white contrast that hurts the eyes. I’d love for background as well, but we only have four choices.

But there’s a little bit of nuance in those choices, as he explains: “But I’d switch up color for background on sites with more complex info that requires proper sectioning. In that case I’d also switch margin with padding.”

Amit Sheen

Getting straight to Amit’s selections:

• font
• color
• background
• color-scheme

The choices are largely driven by wanting to combat default user agent styles:

The thing is, if we only have four properties, we end up relying heavily on the user agents, and the only thing I’d really want to change is the fonts. But while we are at it, let’s add some color control. I’m not sure how much I’d actually use them, but it would be good to have them available.

Geoff Graham

Alright, I’m not quite as exciting now that you’ve seen everyone else’s choices. You’ll see a lot of overlap here:

• font: A shorthand for a whopping SEVEN properties for massaging text styles.
• color: Seems like this would come in super handy for establishing a visual hierarchy and distinguishing one element from another.
• padding: I can’t live without a little breathing room between an element’s content box and its inner edge.
• color-scheme: Good minimal theming that’ll work nicely alongside color and support the light-dark() function.

Clearly, I’m all in on typography. That could be a very good thing or it could really constrain me when it comes to laying things out. I really had to fight the urge to use display because I always find it incredibly useful for laying things out side-by-side that wouldn’t otherwise be possible with block-level elements.

Your turn!

Curious minds want to know! Which four properties would you take with you on a desert island?

What’re Your Top 4 CSS Properties? originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

Web forms exist to put information from people into databases. The input fields and formatting rules in online forms are there to make sure the information fits the structure a database needs. But unstructured input in AI-enabled applications means machines, instead of humans, can do this work.

17 years ago, I wrote a book on Web Form Design that started with "Forms suck." Fast forward to today and the sentiment still holds true. No one likes filling in forms but forms remain ubiquitous because they force people to provide information in the way it's stored within the database of an application. You know the drill: First Name, Last Name, Address Line 2, State abbreviation, and so on.

With Web forms, the burden is on people to adapt to databases. Today's AI models, however, can flip this requirement. That is, they allow people to provide information in whatever form they like and use AI do the work necessary to put that information into the right structure for a database.

How does this work? Instead of a Web form enforcing the database's input requirements a dynamic context system can handle it. One way of doing this is with AgentDB's templating system, which provides instructions to AI models for reading and writing information to a database.

With AgentDB connected to an AI model (via an MCP server), a person can simply say "add this" and provide an image, PDF, audio, video, you name it. The model will use AgentDB's template to decide what information to extract from this unstructured input and how to format it for the database. In the case where something is missing or incomplete, the model can ask for clarification or use tools (like search) to find possible answers.

In the example above, I upload a screenshot from Instagram announcing a concert and ask the AI model to add it to my concert tracker. The AgentDB template tells the model it needs Show, Date, Venue, City, Time, and Ticket Price for each database entry. So the AI model pulls this information from the unstructured input (screenshot) and, if complete, turns it into the structured format a database needs.

Of course, the unstructured input can also be a photo, a link to a Web page, a Word document, a PDF file, or even just audio where you say what you want to add. In each case the combination of AI model and AgentDB will fill in the database for you.

No Web form required. And no form is the best kind of Web Form Design.

Color interpolation, loosely speaking, is the process of determining the colors between two color points. It allows us to create unique colors, beautiful palettes, better gradients, and smooth transitions.

I recently wrote a Guide to CSS Color Functions but didn’t have the chance to explain color interpolation in any great depth — which is a shame, since it allows us to create cool demos like this one:

CodePen Embed Fallback

Did you notice how oklch(80% 0.3 340) interpolates to oklch(80% 0.3 60), then to oklch(80% 0.3 180), then to oklch(80% 0.3 270) and back to oklch(80% 0.3 340) using CSS animation? Well, I did! And that’s just a powerful use of interpolation.

Where can we use color interpolation?

Again, color interpolation is all over CSS. These properties and functions support color interpolation either through direct mixing, gradients, or transitions:

• All color gradients, likelinear-gradient(), conic-gradient(), etc.)
• color-mix()
• animation
• transition
• filter
• All functions in the relative color syntax

In gradients and the color-mix() function, we even have a formal syntax for color interpolation:

<color-interpolation-method> = in [ <rectangular-color-space> | <polar-color-space> <hue-interpolation-method>? ] <color-space> = <rectangular-color-space> | <polar-color-space> <rectangular-color-space> = srgb | srgb-linear | display-p3 | a98-rgb | prophoto-rgb | rec2020 | lab | oklab | xyz | xyz-d50 | xyz-d65 <polar-color-space> = hsl | hwb | lch | oklch <hue-interpolation-method> = [ shorter | longer | increasing | decreasing ] hue

Yes, that’s a convoluted definition, but if we go ahead and inspect how this syntax works in color-mix(), for example, we would have something like this:

.element{ color: color-mix(in lch longer hue, red, blue); }

The CSS color-mix() function provides a way for us to mix different colors in any color space, which is all what color interpolation is about: going from color to another.

Our key focus is the in lab longer hue part, which specifies how color-mix() does the interpolation. This is basically saying, “Hey CSS, interpolate the next colors in the CIELCH color space using a longer hue arc.” Yes, the in lab part means the interpolation is done in CIELCH, one of the many CSS color spaces, but we’ll get to what longer hue exactly means later.

Just remember:

• The in keyword always precedes the color interpolation method.
• The second value is the color space used for mixing.
• The third value is an optional hue interpolation method ending with the hue keyword.

This same syntax appears in all gradient functions, where colors are interpolated gradually to get a smooth gradient. Look at how tweaking the gradient with the color interpolation syntax can give us a completely new gradient:

.element { background: linear-gradient(in oklch longer hue 90deg, magenta, cyan); } CodePen Embed Fallback

Let’s backtrack a little, though. Interpolation can occur in two major color spaces: rectangular and polar.

Rectangular color spaces

Rectangular color spaces represent colors using Cartesian coordinates on a three-dimensional plane, which you might already know as the X (horizontal), Y (vertical), and Z (depth) axes on a graph.

Rectangular color spaces are like the same sort of graph, but is a map of color points instead. For example, the sRGB color space has three axes, responsible for the amount of a color’s redness, blueness, and greenness.

Polar color spaces

Polar color spaces also represent colors in a three-dimensional plane, just like rectangular color spaces, but it is shaped like a cylinder instead of a rectangular. A color point is represented by three values:

• The height from the point to the center, usually assigned to lightness or brightness.
• The radial distance from the center, usually assigned to chroma or saturation.
• The angle around the center, assigned to the hue.

Credit: Wikipedia

What makes polar color spaces unique is the hue angle. Since it’s an angle, and they are cyclic (like a continuous circle), we have more options for how it can be interpolated.

Hue interpolation

Think of hue interpolation like finding the distance between the two times on a clock.

Let’s assume the clock can go clockwise (forwards) or counterclockwise (backwards) in time.

The minute hand is at 10 minutes (2). If we want to take the shortest distance between 50 minutes (10), then we would make a counterclockwise turn, like going back in time since that is shorter than moving forward in a clockwise direction.

That’s because if you take the longer route, you’ll have to pass through 3, 4, 5, etc. all the way to 10. Taking the shorter counterclockwise) route , you would reach 10 in less time (15 minutes).

Hue interpolation works similarly. It is a CSS algorithm that determines how you want hue colors in polar color spaces to be mixed, and the direction you want to take between two hue points.

There are four types of hue interpolation in CSS. Let’s go over those next.

shorter and longer

The shorter (default value) hue interpolation method simply takes the shorter route, while the longer hue interpolation method takes the longer route when mixing colors between two hue points.

Imagine blending two hue values red (0deg) and blue (240deg). There are two ways to do this:

• Go the longer route (distance of 240deg).
• Go the shorter route (distance of 120deg).

If shorter is used, the browser takes the shorter route (120deg). Otherwise, if longer is used, the browser takes the longer route (240deg).

CodePen Embed Fallback

This offers up a nice and unique blend of colors depending on your preferences. Hue interpolation is useful in creating smooth color transitions and gradients, giving plenty of life to the websites using color.

The shorter or longer hue interpolation, depending on the shortest or longest distances between two hue value points, can either go clockwise or counterclockwise. We can also set this automatically without actually using one of these keywords, which we will look at next.

increasing and decreasing

Sticking with our clock analogy, the increasing hue interpolation method is like moving the minutes hand from 2 to 10, always in a clockwise direction. Even if the final value is 1, it would still go in a clockwise direction, doing almost a full turn.

If, however, the hue interpolation method is set to decreasing, the minutes hand will always go in a counterclockwise direction. As the specification says, “[d]epending on the difference between the two angles, this will either look the same as shorter or as longer.”

If the angle goes from 20deg to 50deg using the increasing hue interpolation value, the value will move clockwise from 20deg to 50deg, displaying the colors in between. However, if the hue interpolation method is set to decreasing, then the algorithm takes the value from 20deg to 50deg in a counterclockwise direction.

Since increasing means the clock’s minute hand is constantly moving forward, this means the value can reach up to 360deg, a full circle. If the angle reaches 360deg, it resets back to 0deg until it reaches the next point. But if decreasing reaches 0deg, then it resets to 360deg, keeping the hue change consistent.

CodePen Embed Fallback How is this useful?

Yes, all this theory is great: we can use interpolation to get the intermediary color(s) between two colors and make new kinds of colors, but how can we actually use it to create better color experiences in CSS?

Creating gradients

Color interpolation happens frequently in all CSS gradient functions. Take, for example, the conic-gradient() function, which makes it easy to create a smooth transition of colors that rotate around a center point:

background: conic-gradient( from 0deg, oklch(70% 0.3 0deg), oklch(70% 0.3 120deg), oklch(70% 0.3 240deg), oklch(70% 0.3 360deg) ); CodePen Embed Fallback

Notice how the hue blends smoothly between each color stop point? It’s beautiful.

Color mixing

Reading about color-mix() in the CSS-Tricks Almanac will give you a basic idea of how this is done, but if you’re like me and want the raw code, here it is:

/* First Box */ background-color: color-mix(in oklch, rgb(255 0 0) 50%, lch(60% 40% 220deg) 50%); /* Second Box */ background-color: color-mix(in oklch longer hue, rgb(255 0 0) 50%, lch(60% 40% 220deg) 50%); CodePen Embed Fallback

A great advantage of color-mix() is that you gain the ability to mix colors in different color spaces within another color space, thereby producing a unique color. Again, it’s moving from one color into another and the direction we take for mixing colors matters.

Animation

We can animate the transition between colors! So, instead of mixing two specific points, we can watch the color transition between all of the colors in between the two points!

@keyframes bg-shift { from { background-color: oklch(30% 0.3 20deg); /* dark pink */ } to { background-color: oklch(70% 0.3 200deg); /* Cool bluish */ } } CodePen Embed Fallback References

• Okay, Color Spaces by Eric Portis
• ColorAide Color Interpolation Documentation
• CSS Color Module Level 4
• Interpolating Colors by Chris Brunell

What You Need to Know About CSS Color Interpolation originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

Applications built on top of large-scale AI models benefit from the AI model's built-in capabilities without requiring app developers to write additional code. Essentially if the AI model can do it, an application built on top of it can do it as well. To illustrate, let's look at the impact of a model's World knowledge on an app.

For years, software applications consisted of running code and a database. As a result, their capabilities were defined by coded features and what was inside the database. When the running code is replaced by a large language model (LLM), however, the information encoded in model's weights instantly becomes part of the capabilities of the application.

With AI apps, end users are no longer constrained by the code developers had the time and foresight to write. All the World knowledge (and other capabilities) in an AI model are now part of the application's logic. Since that sounds abstract let's look at a concrete example.

I created an AI app with AgentDB by uploading a database of NBA statistics spanning 77 years and 13.6 million play-by-play records. When I add the MCP link AgentDB makes for me to Anthropic's Claude, I have an application consisting of a database optimized for AI model use, and an AI model (Claude) to use as the application's brain. Here's a video tutorial on how to do this yourself.

In the past a developer would need to write code to render the user interface for an application front-end to this database. That code would determine what kind of questions people could get answers to. Usually this meant a bunch of UI input elements to search and filter games by date, team, player, etc. The NBA's stats page (below) is a great example of this kind of interface.

But no matter how much code developers write, they can't cover all the ways people might want to interact with information about the NBA's 77 years. For instance, a question like "What were the last 5 plays in the Malice in the Palace game?" requires either running code that can translate malice in the palace to a specific date and game or an extra field in the database for game nicknames.

When a large language model is an application's compute, however, no extra code needs to be written. The association between Malice in the Palace and November 19, 2004 is present in an AI model's weights and it can translate the natural language question into a form the associated database can answer.

An AI model can use its World knowledge to translate people's questions into the kind of multi-step queries needed to answer what seem like simple questions. Consider the example below of: "Who was the tallest player drafted in Ant-Man’s NBA draft class?" We need to figure what player Ant-Man refers to, what year he was drafted, who else was drafted then, get all their heights, and then compare them. Not a simple query to write by hand but with AI acting as an application's brain... it's quick and easy.

World knowledge, of course, isn't the only capability built-in to large-language models. There's multi-language support, vision (for image parsing), tool use, and more emerging. All of these are also application capabilities when you build apps on top of AI models.

One of the newer CSS features that has piqued my interest: the light-dark() function. And I’ve been closely following it ever since it became Baseline back in May 2024.

The light-dark() function, briefly

If you don’t know, the light-dark() function takes two color arguments: one for light mode and one for dark mode. Hence, the name light-dark(). It toggles between the two light and dark values based on a user’s preferences. Sara Joy has a wonderful article where you can get a much more detailed explanation.

The key thing is that the function requires you to use the color-scheme property to activate those two color modes:

:root { color-scheme: light dark; } .element { color: light-dark(brown, black); }

And, depending on the user’s preference, one of those two modes is applied.

Just two modes?

That said, I’ve been wondering for a while now: Should the light-dark() function support more than light and dark color modes?

I wrote about light-dark() for the CSS-Tricks Almanac. During my research, I found myself wishing the function could do more, specifically that it lacks support for other types of color schemes that a user might prefer, such as grayscale, high contrast, and low contrast.

Does light-dark() even need a high-contrast mode?

I’d say both yes and no. Let’s go back in time to when light-dark() was initially proposed somewhere around 2022. Emilio Cobos asked for a function to support light and dark mode changes, and it was added to the specifications.

Done and handled, right? Not so fast. The ticket was indeed closed when Jacob Miller chimed in:

Just saw this from @bramus‘s post, and I suspect that things are already closed / there’s no changing things now, but I see this as an approach that doesn’t actually solve for the issues people are facing with theming, and does so in a way that will create a trap for them when pursuing proper theming support.

[…]

We shouldn’t ship single-purpose tools for the browser, but rather ones that scale and we can build upon.

Good thing he chimed in, because that prompted Bramus to reopen the ticket:

I think this was mistakingly done so. The end goal is to have something like schemed-value(), with light-dark() being an intermediary step towards the final solution.

That’s a big deal! Bramus is saying that the light-dark() function is an intermediary solution on the way to a  schemed-value() function. In other words, shipping light-dark() was never the intended end goal. It’s a step along the way to this other more robust schemed-value() feature.

Custom color schemes

Bramus has already written a bunch about the schemed-value() concept. It could look something like this:

:root { color-scheme: dark light custom; } body { color: schemed-value( light lightblue, /* Value used for light color-scheme */ dark crimson, /* Value used for dark color-scheme */ --custom green /* Value used for --custom color-scheme */ ); }

This isn’t possible with light-dark(). In fact, before the function can support more than two modes, the color-scheme property has to be extended with more than the light and dark values. Only then can light-dark() be extended because, remember, light-dark() needs the color-scheme property in order to do its thing.

Specifically, we’d need color-scheme to accept some sort of “custom” color scheme value. Tab Atkins provides a possible example in the ticket. The idea is to register a custom color scheme using a @color-scheme at-rule that defines the scheme’s properties, such as what particular color keywords are mapped to, and then use that color scheme’s ident on the color-scheme property that is declared on the root element:

@color-scheme --high-contast { base-scheme: dark; canvascolor: black; canvastext: white; accentcolor: white; /* other properties set to specific colors */ } html { color-scheme: --high-contrast; }

With that in place, the custom color scheme can be used as its own standalone value in the forthcoming schemed-value() function:

@color-scheme --high-contast { /* ... */ } html { color-scheme: --high-contrast light dark; } body { color: schemed-value(--high-contrast, black, white); }

Breaking it all down:

• We register a custom color scheme (e.g. --high-contrast) in a @color-scheme at-rule.
• We define the color scheme’s properties in the at-rule, such as whether its base theme is light or dark and what certain values color keywords map to.
• We declare the custom color scheme on the color-scheme property at the root level (i.e., html { color-scheme: --high-contrast;}).
• We apply the custom color scheme by declaring it on color-related properties by way of the schemed-value() function.

So, not only will light-dark() change, the CSS color-scheme property will most likely have its own at-rule to allow for custom color-scheme values.

We need more color theme support, but not in light-dark()

This begs my earlier question: Does the light-dark() function really need to support more than two color scheme modes? Bramus has an answer:

When schemed-value() ever becomes a thing, light-dark() would become syntactic sugar for it.

A-ha! This means light-dark() doesn’t need to support multiple modes because schemed-value() has the power to extend light-dark() by its own virtue:

light-dark(<color>, <color>); = schemed-value(light <color>, dark <color>);

Is light-dark() an intermediary step? Yes, it is. And should it be extended to support multiple modes, including custom color schemes? It certainly could, but it doesn’t have to be. Instead, we can register and define a custom color scheme in an at-rule and make sure the color-scheme property can read it. That way, we get the simplicity of a two-mode function that can be further abstracted to support additional custom modes, if needed.

In fact, it goes beyond color schemes. There is even an open ticket to extend light-dark() for images, and the discussions surrounding it seem to agree on a new function specifically designed for it.

What about custom functions?

But, wait! Doesn’t a lot of this sound a lot like what we’ve been hearing about the work happening with custom functions? Indeed, Tab came back with a possible approach using the if() function, and the Chris Lilley retagged the ticket as a result. That’s when Bramus demonstrated how we could reasonably replicate the light-dark() function with a custom CSS function:

:root { /* ensures light mode comes first */ --scheme: light; /* dark mode is set here */ @media (prefers-color-scheme: dark) { --scheme: dark; } } /* custom function returns any two values depending on whether system is in light or dark mode */ @function --light-dark(--light-color, --dark-color) { result: if(style(--scheme: dark): var(--dark-color) ; else: var(--light-color)); } p { font-size: --light-dark( 2rem, 2.5rem ); /* returns 2rem if system is in light mode and 2.5rem if system is in dark mode */ }

Nothing is set in stone! The only thing we know for sure is that we have a working light-dark() function and it’s Baseline widely available for use. Custom functions a work in progress and only available in Chromium-based browsers at the time I’m writing this.

The path forward

I’ve been exploring everything color-related for a while now, and I’d like to know your thoughts: Are you excited about the upcoming changes to light-dark()? Do you think light-dark() should support more color modes like high contrast?

Let me know your thoughts in the comment section below. Feel free to also comment on any of the W3C GitHub comment threads linked in this post to share your thoughts and concerns for the coming new features.

More on light-dark() Almanac on Oct 7, 2025 light-dark() html { color: light-dark(#000, #fff); } accessibility color Sunkanmi Fafowora Article on Oct 29, 2024 Come to the light-dark() Side Sara Joy Article on Jun 5, 2025 Exploring the CSS contrast-color() Function… a Second Time Daniel Schwarz Article on Jun 26, 2025 Poking at the CSS if() Function a Little More: Conditional Color Theming CSS functions Daniel Schwarz

Should the CSS light-dark() Function Support More Than Light and Dark Values? originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.

Read the book, Typographic Firsts

Without screwing up the space/time continuum, if I could go back in time, let’s say 45 years ago when I edited, art directed and designed underground tabloid magazine-newspapers, and I could take back a contemporary font family to use as the exclusive typeface for one of those periodicals, I would choose Ritualist designed by Justin […]

The post Steven Heller’s Font of the Month: Ritualist appeared first on I Love Typography.

As the proliferation of AI-powered chat interfaces in software continues, people increasingly take one of two sides. Chat is the future of all UI or chat is a terrible UI. Turns out there's reason to believe both, here's a bunch of them.

Back in 2013, I proposed a variant of Jamie Zawinski's popular Law of Software Envelopment reframed as:

Every mobile app attempts to expand until it includes chat. Those applications which do not are replaced by ones which can.

Today every major mobile app has some form of chat function whether social network, e-commerce, ride-share, and so on. So chat is already pervasive and thereby familiar, which made it a great interface to usher in the age of AI. But is it AI's final form?

“Chat is the future of software.”

• People already know how to use chat interfaces. This familiarity means people can jump right in and start using powerful AI systems.
• An empty text box is great at capturing user intent: people can simply tell chat apps what they want to get done. “Just look at Google.”
• Natural language allows people to communicate what they want like they would in the real World, no need to learn a UI.
• The best interface is…  no interface, an invisible interface, etc.
• Conversational interfaces can shift topics and goals, providing a way to compose information and actions that’s just right for specific. needs.
• Voice input means people don’t have to type but can still simply chat with powerful systems.
• Chat user interfaces for AI models are a fundamental shift from forcing humans to learn computers to computers understanding human language.

“Chat is a terrible user interface.”

• Chat interfaces face the classic "invisible UI" problem: without clear affordances, people don't know what they can do, nor how to get the best results from them.
• Walls of text are suboptimal to communicate and display complex information and relationships unlike images, tables, charts, ad more.
• Scrolling through conversation threads to find and extract relevant information is painful, especially as chat conversations run long.
• Context gets lost in back and forth interactions which slow everything down. Typing everything you want to do is cumbersome.
• Language is a terrible way to describe visual, spatial, and temporal things.
• Voice-based interfaces make it even harder to communicate information better suited to images and user interfaces.
• We’re very early in the evolution of AI-powered software and lots of different and useful interfaces for interacting with AI will emerge.

It's also worth noting that chat isn't the only way to integrate AI in software products and increasingly agent-based applications outperform chat-only solutions. So expect things to keep changing.

Editor’s note: This is a really clever idea that Preethi shared, but you will also see that it comes with accessibility drawbacks because it uses duplicated interactive elements. There are other ways to approach this sort of thing, as Preethi mentions, and we’ll look at one of them in a future article.

Two large pizzas for yourself, or twelve small ones for the kids party — everyone’s gone through the process of adding items to an online cart. Groceries. Clothing. Deli orders. It’s great when that process is simple, efficient, and maybe even a little quirky.

This post covers a design referred as infinite selection. Metaphorically infinite.

Here’s how it works:

CodePen Embed Fallback

That’s right, you click an item and it jumps right into the shopping cart, complete with a smooth transition that shows it happening. You can add as many items as you want!

And guess what: all of it is done in CSS — well, except the part that keeps count of selected items — and all it took is a combination of radio form inputs in the markup.

I’m going to walk you through the code, starting with the layout, but before that, I want to say up-front that this is just one approach. There are for sure other ways to go about this, and this specific way comes with its own considerations and limitations that we’ll get into.

The Layout

Each item (or product, whatever you want to call it) is a wrapper that contains two radio form inputs sharing the same name value — a radio group.

<div class="items flat-white"> <input type="radio" name="r3" title="Flat White"> <input type="radio" name="r3" title="Flat White"> </div>

When you check one in a duo, the other gets unchecked automatically, leading to a see-saw of check and uncheck between the two, no matter which one is clicked.

Each item (or radio group) is absolutely positioned, as are the two inputs it contains:

.items { position: absolute; input { position: absolute; inset: 0; } }

The inset property is stretching the inputs to cover the entire space, making sure they are clickable without leaving any dead area around them.

Now we arrange everything in a layout. We’ll use translate to move the items from a single point (where the centered cart is) to another point that is a litte higher and spread out. You can code this layout anyway you like, as long as the radio buttons inside can make their way to the cart when they are selected.

.items { --y: 100px; /* Vertical distance from the cart */ &:not(.cart) { transform: translate(var(--x), calc(-1 * var(--y))); } &.espresso { --x: 0px; /* Horizontal dist. from the cart */ } &.cappuccino { --x: -100%; } &.flat-white { --x: 100%; } }

So, yeah, a little bit of configuration to get things just right for your specific use case. It’s a little bit of magic numbering that perhaps another approach could abstract away.

Selecting Items

When an item (<input>) is selected (:checked), it shrinks and moves (translate) to where the cart is:

input:checked { transform: translate(calc(-1 * var(--x)), var(--y)) scale(0); }

What happens under the hood is that the second radio input in the group is checked, which immediately unchecks the first input in the group, thanks to the fact that they share the same name attribute in the HTML. This gives us a bit of boolean logic a là the Checkbox Hack that we can use to trigger the transition.

So, if that last bit of CSS moves the selected item to the shopping cart, then we need a transition to animate it. Otherwise, the item sorta zaps itself over, Star Trek style, without you telling.

input:checked{ transform: translate(calc(-1 * var(--x)), var(--y)) scale(0); transition: transform .6s linear; } Keeping Count

The whole point of this post is getting a selected item to the cart. There’s no “Cart” page to speak of, at least for the purposes of this demo. So, I thought it would be a good idea to show how many items have been added to the cart. A little label with the count should do the trick.

let n = 0; const CART_CNT = document.querySelector("output"); document.querySelectorAll("[type='radio']").forEach(radio => { radio.onclick = () => { CART_CNT.innerText = ++n; CART_CNT.setAttribute("arial-label", `${n}`) } });

Basically, we’re selecting the cart object (the <output> element) and, for each click on a radio input, we increase an integer that represents the count, which is slapped onto the shopping card icon as a label. Sorry, no removing items from the cart for this example… you’re completely locked in. &#x1f605;

Accessibility?

Honestly, I wrestled with this one and there probably isn’t a bulletproof way to get this demo read consistently by screen readers. We’re working with two interactive elements in each group, and need to juggle how they’re exposed to assistive tech when toggling their states. As it is, there are cases where one radio input is read when toggling into an item, and the other input is read when toggling back to it. In other cases, both inputs in the groups are announced, which suggests multiple options in each group when there’s only one.

I did add a hidden <span> in the markup that is revealed with keyboard interaction as a form of instruction. I’ve also inserted an aria-label on the <output> that announces the total number of cart items as they are added.

Here’s the final demo once again:

CodePen Embed Fallback Maybe Use View Transitions Instead?

I wanted to share this trick because I think it’s a clever approach that isn’t immediately obvious at first glance. But this also smells like a situation where the modern View Transition API might be relevant.

Adrian Bece writes all about it in a Smashing Magazine piece. In fact, his example is exactly the same: animating items added to a shopping cart. What’s nice about this is that it only takes two elements to build the transition: the item and the cart label. Using CSS, we can hook those elements up with a view-transition-name, define a @keyframes animation for moving the item, then trigger it on click. No duplicate elements or state juggling needed!

Alternatively, if you’re working with just a few items then perhaps a checkbox input is another possible approach that only requires a single element per item. the downside, of course, is that it limits how many items you can add to the card.

But if you need to add an infinite number of items and the View Transition API is out of scope, then perhaps this radio input approach is worth considering.

A Radio Button Shopping Cart Trick originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.