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 animations, enter/exit transitions, icon animations, scale on press, motion restraint
Icons	Icon stroke weight, states via currentColor, outline vs fill, sizing, RTL flipping
Performance	Transition specificity, will-change usage

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.

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.

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. Never use a value smaller than 0.95: anything below feels exaggerated. Add a static prop to disable it when motion would be distracting.

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. Never Use transition: all

Always specify exact properties: transition-property: scale, opacity. Tailwind's transition-transform covers transform, translate, scale, rotate.

12. 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.

13. 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.

14. 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.

15. 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
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

Review Output Format

Use this format only when the user asks for a standalone UI-polish review. When better-interface orchestrates the review, provide domain evidence and findings to that skill and let its output format, severity scale, consolidation rules, cap, and verdict take precedence.

Present the standalone review in two parts.

Findings

Group all confirmed findings by principle. Use a markdown table with Severity, Location, Before, After, and Why columns. Never use separate "Before:" / "After:" lines.

• Severity: HIGH makes an interaction misleading, unresponsive, or repeatedly disruptive; MEDIUM creates a noticeable craft or consistency problem; LOW is isolated polish.
• Location: cite path/to/file:line. If the artifact has no source files, cite the exact screen and component instead.
• Before / After: show the current implementation and an actionable replacement.
• Why: name the violated principle and explain how it affects the interface.

Consolidate a repeated systemic issue into one row and list every affected location. Omit principles with no findings.

Example

Concentric border radius

Severity	Location	Before	After	Why
LOW	src/Card.tsx:28	rounded-xl on card + rounded-xl on inner button (p-2)	rounded-2xl on card (8 + 8 = 16), rounded-lg on inner button	Nested corners should be concentric
LOW	src/card.css:11	border-radius: 16px on both nested surfaces	Outer 24px, inner 16px with 8px padding	Equal nested radii make the inner surface look pinched

Scale on press

Severity	Location	Before	After	Why
LOW	src/Button.tsx:19	<button className="...">	Add active:scale-[0.96] transition-transform	Press feedback makes the control feel responsive
MEDIUM	src/button.css:24	scale(0.9) on press	Raise to scale(0.96)	Anything below 0.95 feels exaggerated

Verification and Verdict

After the findings:

1. Verification: list the exact checks run and their observed results. Walk every relevant state and inspect motion at 10% speed when animation is involved. If a check was not run, state what still needs verification.
2. Verdict: Block if any HIGH finding remains, Needs changes if only MEDIUM or LOW findings remain, and Approve only when no actionable findings remain.

When there are no findings, omit the tables, state "No actionable UI-polish findings", report verification, and end with Approve.