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

Core Principles

1. Concentric Border Radius

outerRadius = innerRadius + 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 need manual adjustment — icon-side padding = text-side padding - 2px.

3. Shadows Over Borders

Layer multiple transparent box-shadow 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 translateY(-12px) instead of full height. Exits should be softer and shorter than enters.

7. Contextual Icon Animations

Animate icons with opacity, scale (0.25→1), and blur (4px→0). Use spring with bounce=0 if Motion available; CSS cross-fade if not.

8. Font Smoothing

Apply -webkit-font-smoothing: antialiased on macOS for crisper text.

9. Tabular Numbers

Use font-variant-numeric: tabular-nums for dynamically updating numbers to prevent layout shift.

10. Text Wrapping

text-wrap: balance on headings (≤6 lines). text-wrap: pretty on body text to avoid orphans.

11. Image Outlines

Add 1px outline: pure black rgba(0,0,0,0.1) in light mode, pure white rgba(255,255,255,0.1) in dark mode. Never use tinted neutrals.

12. Scale on Press

scale(0.96) on click gives buttons tactile feedback. Never below 0.95. Add static prop to disable when distracting.

13. Skip Animation on Page Load

initial={false} on AnimatePresence for default-state elements. Verify it doesn't break intentional entrance animations.

14. Never Use transition: all

Always specify exact properties. Tailwind: transition-transform or transition-[scale,opacity].

15. Use will-change Sparingly

Only for transform, opacity, filter — GPU-compositable properties. Never will-change: all. Only add when you notice first-frame stutter.

16. Minimum Hit Area

44×44px for touch/mobile, ≥40×40px for dense desktop. Extend with pseudo-element. Never let two hit areas overlap.

Common Mistakes

Review Output Format

Always present changes as a markdown table with Before and After columns. Group by principle with a heading. Only include principles where changes were made — omit empty tables.

Example

Concentric border radius

Scale on press

Review Checklist

• Nested rounded elements use concentric border radius
• Icons are optically centered, not just geometrically
• Shadows used instead of borders where appropriate
• Enter animations are split and staggered
• Exit animations are subtle
• Dynamic numbers use tabular-nums
• Font smoothing is applied
• Headings use text-wrap: balance
• Images have subtle outlines (pure black/white, not tinted)
• Buttons use scale(0.96) on press where appropriate
• AnimatePresence uses initial={false} for default-state elements
• No transition: all — only specific properties
• will-change only on transform/opacity/filter, never all
• Interactive elements have ≥44×44px hit areas (touch) or ≥40×40px (desktop)