Make Interfaces Feel Better

Source: salvaged from stale community PR #1659 by linus707.

Core Principles

Concentric Radius

For nearby nested rounded surfaces:

outer radius = inner radius + padding

If padding is large, treat layers as separate surfaces instead of forcing the math. The point is optical coherence, not formula worship.

Optical Alignment

Geometric centering is not always visual centering. Icon buttons, play triangles, arrows, stars, and asymmetric icons often need a small offset. Fix the SVG when possible; otherwise adjust with a pixel-level margin or padding change.

Shadows And Borders

Use borders for separation and focus rings. Use layered shadows when a card, button, dropdown, or popover needs depth. Shadows should be transparent and subtle enough to work across backgrounds.

Text Wrapping

• Use text-wrap: balance on headings and short titles.
• Use text-wrap: pretty on short-to-medium body text, captions, descriptions, and list items.
• Avoid both on long prose, code, and preformatted content.
• Use font-variant-numeric: tabular-nums for counters, timers, prices, tables, and other updating numbers.

Font Smoothing

On macOS, apply antialiased font smoothing at the root layout when the project does not already do so:

html {
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

Image Outlines

Images often need a subtle inset outline so their edges do not blur into the surface.

img {
  outline: 1px solid rgba(0, 0, 0, 0.1);
  outline-offset: -1px;
}

@media (prefers-color-scheme: dark) {
  img {
    outline-color: rgba(255, 255, 255, 0.1);
  }
}

Use neutral black or white alpha outlines. Do not tint image outlines with the brand palette.

Motion

Use CSS transitions for interactive state changes because they can retarget when the user changes intent mid-motion. Reserve keyframes for staged one-shot entrances or loading sequences.

Good motion defaults:

• Enter: combine opacity, small translateY, and optionally blur.
• Exit: shorter and quieter than enter, usually 150ms.
• Press: scale(0.96) for tactile buttons, with a way to disable it when the movement distracts.
• Icon swaps: cross-fade with opacity, scale, and blur instead of instant visibility toggles.

Transition Scope

Never use transition: all. Specify the changed properties:

.button {
  transition-property: transform, background-color, box-shadow;
  transition-duration: 150ms;
  transition-timing-function: ease-out;
}

Use will-change only for first-frame stutter on compositor-friendly properties such as transform, opacity, and filter. Never use will-change: all.

Hit Areas

Interactive controls should have at least a 40x40px hit area, ideally 44x44px where the layout allows it. Expand with a pseudo-element when the visible icon is smaller, but do not let expanded hit areas overlap.

Review Output

When reviewing a UI polish pass, report concrete changes in before/after rows:

Include file paths and properties when they are not obvious from the snippets. Omit principles that you checked but did not change.

Checklist

• Nested rounded elements are optically coherent.
• Icons are visually centered.
• Buttons, cards, and popovers use borders or shadows for the right reason.
• Headings and short text avoid awkward wrapping.
• Dynamic numbers use tabular numerals.
• Images have neutral outlines where needed.
• Enter and exit animations are split, subtle, and interruptible where appropriate.
• Buttons have tactile active states without exaggerated motion.
• transition: all and will-change: all are absent.
• Small controls still have usable hit areas.