The latest CSS features, similar to What you need to know about modern CSS (2025 edition) from Frontend Masters

Note animations does not work on Firefox.

1) Top-Level Media Query
2) Nested Media Query
3) Variablizing the Columns
4) Using a Custom Function
5) Custom Function + if()

Fix the overflow on hover correctly

The snippet:

legend {
  padding: 0;
  display: table;
}
fieldset {
  border: 0;
  padding: 0.01em 0 0 0;
  margin: 0;
  min-width: 0;
}
body:not(:-moz-handler-blocked) fieldset {
  display: table-cell;
}

-apple-visual-effect: -apple-system-glass-material;

Whoever it was at Apple that decided to make this a CSS property is a genius because it makes it incredibly easy to provide different rules based on Liquid Glass support.

But it's not documented! So we can assume Apple use the property somewhere in a WebView in order to make the web app looks like native.

Similar to tailwind, but somehow better?

CSS anchor positioning includes many advantages!

It can be placed upon an element, origin from the center of the element, or next to it with position-area inside a 3x3 grid area. The position-area can span cells.
It can also have fallbacks with flip-blocks, flip-inline and flip-start.

Related CSS properties:

• anchor-name
• position-anchor
• position-area
• position-try-fallbacks

The post does not relate how to handle spacing though.

em unit compound when value are greater or lower than 1.
Except that, they are awesome :)

Interactive examples for CSS grid, flexbox, the edge case with absolute positioning.

I didn't know flex with safe that preserves the alignment with the scrollbar.

How CSS handles things already.

#todo what does CSS handle?

interpolate-size is a way to animate height: auto or width. It is only supported in Chrome for now.

A quick example:

@supports (interpolate-size: allow-keywords) {
  :root {
    interpolate-size: allow-keywords;
  }

  details {
    transition: height 0.5s ease;
    height: 2.5rem;

    &[open] {
      height: auto;
      overflow: clip;
    }
  }
}

A more generic one:

:root {
  interpolate-size: allow-keywords;
}

details {
  --calculated-details-padding: var(--details-padding, 1em);

  transition: height var(--details-transition-speed, 150ms) linear;
  height: calc(1lh + (var(--calculated-details-padding) * 2));
  padding: var(--calculated-details-padding);
  background: var(--details-bg, white);
  color: var(--details-color, currentColor);
}

details[open] {
  height: auto;
  overflow: clip;
}

If the maximum font size is less than or equal to 2.5 times the minimum font size, then the text will always pass WCAG SC 1.4.4, at least on all modern browsers.

The author also cites https://utopia.fyi/type/calculator/

How to load font the most efficient way in 2025 for nearly every cases.

To keep the code maintainable, keep the css specificity as low as possible.

BEM falls short: class names can get really long; reusability might not be prioritized; and things must be named.

Another case is to use utility classes (atomic css) to avoid css specificity.

A new approach is with cascade layers.

Anyways, Cascade Layers (@layers) groups styles and declares what order the groups should be, regardless of the specificity scores of those rules.

Each has a sweet spot:

• BEM for clear design system that needs to be consistent; team with different philosophies; styles are less likely to leak between components.
• utility classes: build fast, like prototypes or MVPs and component based JS framework
• cascade layers: legacy codebases where you need full specificity control; integrate third party libraries or styles from other sources; working on a large, complex application or projects with long-term maintenance

How they can work together?
The cascade layers can be seen as an orchestrator: one layer for components (BEM); one layer for utilities (utility classes)

While the CSS specificity is low, everything else is kept simple.

Only up the specificity lightly, and note it; the minimum is another class, :where() or the HTML tag.

A single class ".override" can also be used; but "If you’re ever overriding an override, that’s a good place to stop and re-consider. "

Instead of specifying Block or Element specific Modifiers, you create generic semantic classes that apply those repeatable styles to any element that needs them.

When I started creating Kelp, I went down the BEM path. I quickly switched to semantic CSS, and the file size decreased dramatically as a result.

After programming for years, I find creating a class system is better than BEM.

TL;DR js solutions is often better for accessibility. At least information is conveyed.

Popover will be more useful than ever.

The tradeoff is currently the <details> tag with two limitations: the element does not announce a navigation menu is exposed; clicking outside or pressing Esc does nothing.

The author of Kelp use public and private cascade layer.

Public layers are: theme, extend, overrides and effects.