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.
Quick Reference
| Category | When to Use |
|---|
| Typography | Text wrapping, font smoothing, tabular numbers |
| Layout & Spacing | Border radius, optical alignment, shadows, image outlines |
| Animations | Interruptible animations, enter/exit transitions, icon animations |
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 Over Borders
Layer multiple transparent
values for natural depth. Shadows adapt to any background; solid borders don't.
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
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
instead of full height. Exits should be softer than enters.
7. Contextual Icon Animations
Animate icons with
,
, and
instead of toggling visibility. Spring animations work well here.
8. Font Smoothing
Apply
-webkit-font-smoothing: antialiased
to the root layout on macOS for crisper text.
9. Tabular Numbers
Use
font-variant-numeric: tabular-nums
for any dynamically updating numbers to prevent layout shift.
10. Text Wrapping
Use
on headings. Use
for body text to avoid orphans.
11. Image Outlines
Add a subtle
outline with low opacity to images for consistent depth.
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 with transparency |
| Jarring enter/exit animations | Split, stagger, and keep exits subtle |
| Numbers cause layout shift | Apply |
| Heavy text on macOS | Apply to root |
Review Checklist
Reference Files
- typography.md — Text wrapping, font smoothing, tabular numbers
- layout-and-spacing.md — Border radius, optical alignment, shadows, image outlines
- animations.md — Interruptible animations, enter/exit transitions, icon animations