Design engineering principles for making interfaces feel polished. Use when building UI components, reviewing frontend code, implementing animations, hover states, shadows, borders, micro-interactions, enter/exit animations, or any visual detail work. Triggers on UI polish, design details, "make it feel better", "feels off", stagger animations, border radius, optical alignment, image outlines, box shadows.
Real-world examples
Live HTML demos for this skill — rendered directly in the page. 4 examples.
- 01
Concentric surfaces & shadows
Nested radii use outer = inner + padding; layered transparent box-shadows replace hard borders; images get pure black/white inset outlines.
- 02
Optical alignment & hit areas
Play triangles shift right, icon-side padding is tighter, and small controls expand to 44×44px hit areas without overlapping.
- 03
Staggered enter, subtle exit
Content splits into chunks with ~100ms stagger (opacity + blur + translateY); exits use a soft −12px lift at 150ms, not a dramatic collapse.
- 04
Scale on press & icon swaps
Buttons use scale(0.96) via interruptible transitions; play/pause icons cross-fade with scale 0.25→1, opacity, and blur — never transition: all.
Skill markdown
# UI polish This skill holds the visual polish for surfaces, icons and motion, with the exact value each detail takes. It applies once the underlying interaction is sound, and a polish finding never outranks a broken interaction. ## Exact values, optional polish The values below are exact, not ranges to approximate. `cubic-bezier(0.2, 0, 0, 1)` is not `cubic-bezier(0.4, 0, 0.2, 1)`, and `0.96` is not `0.95`. The optical nudges and the concentric padding cutoff are the exceptions. They are starting points, judged by eye. Keep the project's component library, tokens and density, and match its motion language wherever no rule here gives a value. A deliberate and consistent project convention, such as a style with no shadows, is a preference and not a finding. The same detail done two ways within the project is a finding. Text wrapping, font rendering, tabular numbers and text spacing belong to `better-typography`. Hit areas, keyboard support, ARIA and the reduced-motion requirement belong to `better-accessibility`. Grouping, section spacing, breakpoints and spatial RTL belong to `better-layout`, except directional icon mirroring. Color tokens and contrast measurement belong to `better-colors`. ## Outer radius equals inner radius plus padding Where nested surfaces share a visible, even inset, the outer radius is the inner radius plus the padding plus any border width. Past `24px` of padding, or where the padding is deliberately asymmetric, treat the layers as separate surfaces and keep each one's radius token. Recipes are in [surfaces.md](surfaces.md). ## Align optically where geometry looks off Where geometric centering looks off, nudge by eye. Give a button `2px` less padding on its icon side, shift a play triangle toward its point and fix asymmetric glyphs in the SVG itself. Recipes are in [surfaces.md](surfaces.md#optical-alignment). ## Shadows for elevation, borders for structure Where a border exists only to create depth, replace it with layered transparent `box-shadow` values. Keep borders on dividers, separators, table cells and selected states. Keep them on form inputs too, whose boundary needs 3:1 non-text contrast under `better-accessibility`. Focus rings belong to `better-accessibility` as well. Forced-colors mode removes every `box-shadow`. Keep `border: 1px solid transparent` under a shadow ring so that mode still draws an edge. Recipes are in [surfaces.md](surfaces.md#shadow-recipes). ## Outline images in pure black or white Give content images a `1px` outline inset by `1px`. Use `oklch(0 0 0 / 0.1)` in light mode and `oklch(1 0 0 / 0.1)` in dark. Never use a palette near-black, a tinted neutral or the accent color, because the tint shows as a colored fringe on the image edge. Skip transparent artwork such as logos and illustrations. The recipe is in [surfaces.md](surfaces.md#image-outlines). ## Transitions, not keyframes, for interactive state Drive interactive state changes with CSS transitions or a motion library's springs, which retarget when the user reverses mid-flight. Keyframes run a fixed timeline and cannot reverse, so reserve them for sequences that run once. See [animations.md](animations.md). ## Press scales to 0.96 A pressed button scales to `0.96` over `150ms` with `ease-out`, and a disabled one never scales. Give the button an opt-out where the motion would distract, through the component's existing variant API or a `static` prop. See [recipes for CSS, Tailwind and Motion](animations.md#scale-on-press). ## High-frequency interactions get no animation Keystrokes, row hovers and tab switches get instant feedback, or a transition of `150ms` or less on `opacity` or `background-color`. Reserve expressive motion for infrequent moments such as a view's first load, a success state or an empty state. Every animated state change also leaves a static cue in the form of a color, icon or label. Motion is never the only feedback channel. ## Gate motion behind the reduced-motion preference `better-accessibility` owns the requirement, and no recipe here ships without it. Run movement, scale and blur only under `prefers-reduced-motion: no-preference`. Under reduced motion, replace them with an opacity cross-fade rather than removing the element instantly. Recipes for CSS, Tailwind and Motion are in [animations.md](animations.md#reduced-motion-fallback). ## Stagger infrequent entrances by 100ms Where sequence communicates hierarchy in a staged entrance, split the content into semantic chunks such as title, description and actions. Stagger them `100ms` apart, each entering with opacity, `4px` of blur and `12px` of `translateY` over `300ms` with `ease-out`. Never stagger routine interactions. See [enter-exit.md](enter-exit.md). ## Exits are shorter and smaller than enters Exit with opacity, `4px` of blur and a fixed `-12px` `translateY` over `150ms` with `ease-out`, never the full container height. Slide fully out only where the destination carries meaning, such as a drawer …
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