---
name: make-interfaces-feel-better
description: Design engineering principles for making 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 UI code.

## Quick Reference

| Category | When to Use |
| --- | --- |
| [Typography](typography.md) | Text wrapping, font smoothing, tabular numbers |
| [Surfaces](surfaces.md) | Border radius, optical alignment, shadows, image outlines, hit areas |
| [Animations](animations.md) | Interruptible animations, enter/exit transitions, icon animations, scale on press |
| [Performance](performance.md) | 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.

### 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.

### 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` 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)` — this gives both enter and exit animations without any dependency.

### 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 `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. The color must be pure black in light mode (`rgba(0, 0, 0, 0.1)`) and pure white in dark mode (`rgba(255, 255, 255, 0.1)`) — never a near-black like slate, zinc, or any tinted neutral. A tinted outline picks up the surface color underneath it and reads as dirt on the image edge.

### 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 |
| 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 |

## Review Output Format

Always present changes as a markdown table with **Before** and **After** columns. Include every change you made — not just a subset. Never list findings as separate "Before:" / "After:" lines outside of a table. Group changes by principle using a heading above each table, and keep each row focused on a single diff so the reader can scan the whole list quickly.

### Example

#### Concentric border radius
| Before | After |
| --- | --- |
| `rounded-xl` on card + `rounded-xl` on inner button (`p-2`) | `rounded-2xl` on card (`12 + 8`), `rounded-lg` on inner button |
| `border-radius: 16px` on both nested surfaces | Outer `24px`, inner `16px` with `8px` padding |

#### Tabular numbers
| Before | After |
| --- | --- |
| `<span>{count}</span>` on animated counter | `<span className="tabular-nums">{count}</span>` |
| Default numerals on timer | Added `font-variant-numeric: tabular-nums` to root |

#### Scale on press
| Before | After |
| --- | --- |
| `<button className="...">` | Added `active:scale-[0.96] transition-transform` |
| `scale(0.9)` on press | Raised to `scale(0.96)` — anything below `0.95` feels exaggerated |

Rows should cite the specific file and the specific property that changed when it isn't obvious from the snippet. If a principle was reviewed but nothing needed to change, omit that table entirely — empty tables add noise.

## 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
- [ ] Buttons use scale 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 at least 40×40px hit area

## Reference Files

- [typography.md](typography.md) — Text wrapping, font smoothing, tabular numbers
- [surfaces.md](surfaces.md) — Border radius, optical alignment, shadows, image outlines
- [animations.md](animations.md) — Interruptible animations, enter/exit transitions, icon animations, scale on press
- [performance.md](performance.md) — Transition specificity, `will-change` usage
