Details that make interfaces feel better
Great interfaces rarely come from a single thing. It's usually a collection of small details that compound into a great experience. Apply these principles when building or reviewing UI code.
When reviewing, slow the interface down: replay motion at 10% speed in the browser's Animations panel and walk every state: hover, focus, active, loading, empty. What feels off at 10% speed is what's subtly wrong at full speed.
Preserve the project's component library, tokens, and density. Match its established motion language except where a principle below prescribes an exact interaction pattern.
Typography (text wrapping, font rendering, tabular numbers, spacing) is covered by the better-typography skill; use that for anything text-related. Accessibility (hit areas, focus states, keyboard support, ARIA, reduced motion) is covered by the better-accessibility skill. Layout structure (grouping, spacing between sections, breakpoints, spatial RTL) is covered by the better-layout skill.
Quick Reference
| Category | When to Use |
|---|---|
| Surfaces | Border radius, optical alignment, shadows, image outlines |
| Animations | Interruptible transitions, scale on press, skipping animation on page load, theme switching, motion restraint |
| Enter & Exit | Staged entrances, stagger timing, exit transitions |
| Icon Transitions | Cross-fading an icon on state change, with and without a motion library |
| Icons | Icon stroke weight, states via currentColor, outline vs fill, sizing, RTL flipping |
| Performance | Transition specificity, will-change usage |
| Review Output Format | Severity scale, findings table, verification, verdict |
Core Principles
1. Concentric Border Radius
Outer radius = inner radius + padding. Mismatched radii on nested elements is the most common thing that makes interfaces feel off.
2. Optical Over Geometric Alignment
When geometric centering looks off, align optically. Buttons with icons, play triangles, and asymmetric icons all need manual adjustment.
3. Shadows for Elevation, Borders for Structure
For buttons, cards, and containers whose border exists only to create depth, prefer layered transparent box-shadow values. Keep borders that communicate structure or state: dividers, layout separators, and selected or focus states.
4. Interruptible Animations
Use CSS transitions for interactive state changes: they can be interrupted mid-animation. Reserve keyframes for staged sequences that run once.
5. Split and Stagger Enter Animations
For an infrequent staged entrance where sequence helps communicate hierarchy, break content into semantic chunks and stagger them by ~100ms instead of animating one container. Do not stagger routine, high-frequency interactions. Stagger and exit recipes.
6. Subtle Exit Animations
Use a small fixed translateY instead of full height. Exits should be softer than enters. Use ease-out for both enter and exit transitions.
7. Contextual Icon Animations
Animate icons with opacity, scale, and blur instead of toggling visibility. Use exactly these values: scale from 0.25 to 1, opacity from 0 to 1, blur from 4px to 0px. If the project has motion or framer-motion in package.json, match that package's import path (or the established nearby imports when both exist) and use transition: { type: "spring", duration: 0.3, bounce: 0 }; bounce must always be 0. If no motion library is installed, keep both icons in the DOM (one absolute-positioned) and cross-fade with CSS transitions using cubic-bezier(0.2, 0, 0, 1); this gives both enter and exit animations without any dependency. Both recipes.
8. Image Outlines
Add a subtle 1px outline with low opacity to images for consistent depth. The color must be pure black in light mode (oklch(0 0 0 / 0.1)) and pure white in dark mode (oklch(1 0 0 / 0.1)), never a near-black like slate, zinc, or any tinted neutral. A tinted outline picks up the surface color underneath it and reads as dirt on the image edge.
9. Scale on Press
A subtle scale(0.96) on click gives buttons tactile feedback. Always use 0.96; anything below 0.95 feels exaggerated. Add a static prop to disable it when motion would be distracting. Recipes for CSS, Tailwind, and Motion.
10. Skip Animation on Page Load
Use initial={false} on AnimatePresence to prevent enter animations on first render. Verify it doesn't break intentional entrance animations.
11. Suppress Transitions on Theme Switch
A theme flip changes color, background, border, and shadow on nearly every element at once, so every transition on those properties fires together and the switch smears instead of snapping. Inject *,*::before,*::after{transition:none !important}, force a reflow, then remove it on the next frame. Recipe.
12. Transition Only What Changes
Always specify exact properties: transition-property: scale, opacity. Tailwind's transition-transform covers transform, translate, scale, rotate.
13. Use will-change Sparingly
Only for transform, opacity, filter, the properties the GPU can composite. Never use will-change: all. Only add when you notice first-frame stutter.
14. Match Icon Stroke to Text Weight
An icon next to text carries the text's optical weight: 1.5px stroke beside regular (400) text, 2px beside semibold (600). One stroke weight per icon set; never mix libraries on one surface.
15. One SVG, Recolored per State
Icons use currentColor and get their states (hover, selected, disabled) from CSS color and opacity, never from separate assets. Outline variant is the default; fill variant marks the active state.
16. Motion Restraint
No custom animation on high-frequency interactions: the attention cost repeats on every trigger. Motion is never the only feedback channel; every animated state change also needs a static cue (color, icon, label).
Common Mistakes
| Mistake | Fix |
|---|---|
| Same border radius on closely nested parent and child | Calculate outerRadius = innerRadius + padding |
| Icons look off-center | Adjust optically with padding or fix SVG directly |
| Border used only to fake elevation | Use layered box-shadow with transparency; keep structural and state borders |
| Jarring staged entrance or contextual exit | Stagger infrequent entrances and keep context-preserving exits subtle |
| Stateful icon or toggle animates its default state on page load | Add initial={false} to that AnimatePresence; preserve intentional page entrances |
| Theme toggle crossfades the whole page | Disable transitions for the swap, force a reflow, restore on the next frame |
transition: all on elements | Specify exact properties |
| First-frame animation stutter | Add will-change: transform (sparingly) |
| Hairline icon beside bold text | Match the stroke width to the text weight |
| Separate icon assets per state | One currentColor SVG, states via CSS |
| Filled icons everywhere | Outline as default, fill only for the active state |
| Entrance animation on every hover or keystroke | Instant feedback or ≤150ms opacity/color transition |
Reporting
A standalone UI-polish review is finished when every confirmed finding is reported in the format in review-output.md, with verification and a verdict. Under better-interface, its format governs instead.
