| name | sigil-polish |
| description | Design engineering principles for making Sigil interfaces feel polished. Use when building UI components, reviewing frontend code, implementing animations, hover states, shadows, borders, typography, 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, font smoothing, tabular numbers, image outlines, box shadows. |
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 Sigil UI code.
All visual values must flow through Sigil tokens (var(--s-*)). These principles explain what to do; the token system controls which values to use. Never hardcode colors, shadows, durations, or radii — read them from the active preset.
Quick Reference
| Category | When to Use |
|---|
| Typography | Text wrapping, font smoothing, tabular numbers |
| Surfaces | Border radius, optical alignment, shadows, image outlines, hit areas |
| Animations | Interruptible animations, enter/exit transitions, icon animations, scale on press |
| 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. In Sigil, radii come from var(--s-radius-*) — calculate concentrically from those values.
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 Over Borders
Layer multiple transparent box-shadow values for natural depth. Shadows adapt to any background; solid borders don't. Always use var(--s-shadow-*) tokens.
4. Interruptible Animations
Use CSS transitions for interactive state changes — they can be interrupted mid-animation. Reserve keyframes for staged sequences that run once. Durations come from var(--s-duration-*).
5. Split and Stagger Enter Animations
Don't animate a single container. Break content into semantic chunks and stagger each with ~100ms delay.
6. Subtle Exit Animations
Use a small fixed translateY instead of full height. Exits should be softer than enters.
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, 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).
8. Font Smoothing
Apply -webkit-font-smoothing: antialiased to the root layout on macOS for crisper text. Sigil sets this globally — never override to auto.
9. Tabular Numbers
Use font-variant-numeric: tabular-nums for any dynamically updating numbers to prevent layout shift.
10. Text Wrapping
Use text-wrap: balance on headings. Use text-wrap: pretty for body text to avoid orphans.
11. Image Outlines
Add a subtle 1px outline with low opacity to images for consistent depth.
12. 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.
13. 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.
14. Never Use transition: all
Always specify exact properties: transition-property: scale, opacity. Tailwind's transition-transform covers transform, translate, scale, rotate.
15. Use will-change Sparingly
Only for transform, opacity, filter — properties the GPU can composite. Never use will-change: all. Only add when you notice first-frame stutter.
16. Minimum Hit Area
Interactive elements need at least 40×40px hit area. Extend with a pseudo-element if the visible element is smaller. Never let hit areas of two elements overlap.
Common Mistakes
| Mistake | Fix |
|---|
| Same border radius on parent and child | Calculate outerRadius = innerRadius + padding |
| Icons look off-center | Adjust optically with padding or fix SVG directly |
| Hard borders between sections | Use layered box-shadow with transparency via var(--s-shadow-*) |
| Jarring enter/exit animations | Split, stagger, and keep exits subtle |
| Numbers cause layout shift | Apply tabular-nums |
| Heavy text on macOS | Apply antialiased to root |
| Animation plays on page load | Add initial={false} to AnimatePresence |
transition: all on elements | Specify exact properties |
| First-frame animation stutter | Add will-change: transform (sparingly) |
| Tiny hit areas on small controls | Extend with pseudo-element to 40×40px |
| Hardcoded shadow values | Use shadow-[var(--s-shadow-*)] tokens |
| Hardcoded duration values | Use duration-[var(--s-duration-*)] tokens |
| Hardcoded radii | Use rounded-[var(--s-radius-*)] tokens |
Review Checklist
Reference Files
- typography.md — Text wrapping, font smoothing, tabular numbers
- surfaces.md — Border radius, optical alignment, shadows, image outlines
- animations.md — Interruptible animations, enter/exit transitions, icon animations, scale on press
- performance.md — Transition specificity,
will-change usage
