moai-ref-ui-polish

# UI Polish Reference

## Target Agents

- `manager-develop` - Applies polish rules during frontend/UI component implementation (`cycle_type=tdd` or `cycle_type=ddd` context)
- `/moai review` - UI-design review surface; equivalently available as a per-spawn `Agent(general-purpose)` frontend specialist per `archived-agent-rejection.md` §C

## Core Philosophy

Great interfaces are a collection of small details that compound into a great experience. AI agents frequently miss these details — an `ease-in` easing on an enter animation (should be `ease-out`), a solid border where a semi-transparent shadow reads better, or mismatched radii on nested elements. None of these is catastrophic; together they separate "polished" from "generic".

Before suggesting polish changes, identify the project's existing styling system (design tokens, spacing scale, motion library). Never introduce a second styling system for polish fixes — extend the existing one.

## Geometry and Alignment

| Principle | Rule | Rationale |
|-----------|------|-----------|
| Concentric Border Radius | `outerRadius = innerRadius + padding` | Mismatched radii on nested elements is the most common cause of an interface "feeling off" |
| Optical over Geometric Alignment | When geometric centering looks wrong, align optically | Buttons with icons, play triangles, and asymmetric icons need a manual nudge; geometric center is visually off-center for these shapes |

## Elevation and Structure

| Element | Use | Avoid |
|---------|-----|-------|
| Semi-transparent layered `box-shadow` | Depth, elevation, floating surfaces | Solid borders for depth (they read heavy and flat) |
| Borders | Structure, dividers, separators, selected/focus state | Using shadows for structural separation (ambiguous) |

## Motion

| Pattern | Rule | Common Mistake |
|---------|------|----------------|
| Enter animation easing | `ease-out` (decelerate) — element arrives calmly | `ease-in` on enter (element appears to slam into place) |
| Exit animation easing | `ease-in` (accelerates away), mirroring the enter curve (small fixed `translateY`) | Full-height collapse, or harsher-than-enter motion |
| Interruptible state changes | CSS `transition` (can be interrupted mid-animation) | `keyframes` for interactive states (cannot interrupt) |
| Staged entrances | Stagger semantic chunks ~100ms — only for infrequent staged entrances | Staggering routine, high-frequency interactions (feels sluggish) |
| Contextual icon animation | `opacity`/`scale`/`blur` cross-fade (scale 0.25→1, opacity 0→1, blur 4px→0) | Toggling `visibility` (jarring, no transition) |
| Press feedback | `scale(0.96)` on click — always 0.96 | Smaller than 0.95 (reads as a bug, not a press) |
| First-render enter | Skip with `initial={false}` on `AnimatePresence` (or equivalent) | Enter animation fires on page load (disorienting) |
| Motion restraint | No custom animation on high-frequency interactions; motion is never the only feedback channel | Animating everything (noise, performance cost, accessibility) |

### Motion Easing Values (Web/CSS)

| Case | Value |
|------|-------|
| With motion library (Framer Motion et al.) | `transition: { type: "spring", duration: 0.3, bounce: 0 }` |
| Without motion library (CSS) | `cubic-bezier(0.2, 0, 0, 1)` for the standard "decelerate" curve |
| Never | `transition: all` — always specify exact properties (`transition-property: scale, opacity`) |

### Motion Accessibility and Cost

| Rule | Detail |
|------|--------|
| Reduced-motion branch (required) | Every non-decorative animation needs a `prefers-reduced-motion: reduce` path. Vestibular-disorder users are physically harmed by large-displacement and parallax motion. Reduce to an opacity cross-fade or remove the animation — never merely shorten it. The branch is authored at the same time as the animation, not retrofitted |
| Animate the compositor, not the layout | `transform` and `opacity` are composited and skip layout and most paint. `width`, `height`, `top`, `left`, `margin`, and `padding` trigger layout on every frame (thrashing), which is why the same visual effect janks when driven by the wrong property. Move with `translate`, resize with `scale` |

> Motion principles behind these rules — the three decision passes, motion layers, the
> 1/3 rules, stagger budgets, personality archetypes, Disney-adapted ranges, and the
> emotion-to-motion map — live in `references/motion-principles.md` (L3, load on demand
> when motion is the substance of the work).

## Typography

| Rule | Implementation (Web/CSS) | When |
|------|--------------------------|------|
| Font smoothing | `-webkit-font-smoothing: antialiased` on root layout | macOS targets (sharper rendering) |
| Tabular numbers | `font-variant-numeric: tabular-nums` | Dynamically updating numbers (counters, timers, prices) — prevents layout shift |
| Heading wrapping | `text-wrap: balance` | Headings (prevents orphan words, evens line lengths) |
| Body wrapping | `text-wrap: pretty` | Body paragraphs (avoids orphan widows) |

## Imagery

| Rule | Value |
|------|-------|
| Image outline | `1px` subtle outline at low opacity |
| Outline color (light mode) | pure black — `oklch(0 0 0 / 0.1)` |
| Outline color (dark mode) | pure white — `oklch(1 0 0 / 0.1)` |
| Never | Tinted neutral outlines (read as a color choice, not a separation cue) |

## Interaction

| Rule | Value |
|------|-------|
| Minimum hit area (touch/mobile) | 44 × 44 px |
| Minimum hit area (dense desktop) | 40 × 40 px (extend with pseudo-element if the visual is smaller) |
| Hit area overlap | Never let hit areas overlap |
| Hover on touch (never load-bearing) | `:hover` does not exist on touch — anything reachable only by hover is simply gone on a phone. Keep affordances visible by default and gate hover styling behind `@media (hover: hover) and (pointer: fine)` |
| Hover on pointer (always present) | The inverse rule: on a pointer device every clickable surface needs a distinct hover state,