add frontend skills

skills/frontend-design/reference/typography.md

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+# Typography
+
+## Classic Typography Principles
+
+### Vertical Rhythm
+
+Your line-height should be the base unit for ALL vertical spacing. If body text has `line-height: 1.5` on `16px` type (= 24px), spacing values should be multiples of 24px. This creates subconscious harmony—text and space share a mathematical foundation.
+
+### Modular Scale & Hierarchy
+
+The common mistake: too many font sizes that are too close together (14px, 15px, 16px, 18px...). This creates muddy hierarchy.
+
+**Use fewer sizes with more contrast.** A 5-size system covers most needs:
+
+| Role | Typical Ratio | Use Case |
+|------|---------------|----------|
+| xs | 0.75rem | Captions, legal |
+| sm | 0.875rem | Secondary UI, metadata |
+| base | 1rem | Body text |
+| lg | 1.25-1.5rem | Subheadings, lead text |
+| xl+ | 2-4rem | Headlines, hero text |
+
+Popular ratios: 1.25 (major third), 1.333 (perfect fourth), 1.5 (perfect fifth). Pick one and commit.
+
+### Readability & Measure
+
+Use `ch` units for character-based measure (`max-width: 65ch`). Line-height scales inversely with line length—narrow columns need tighter leading, wide columns need more.
+
+**Non-obvious**: Increase line-height for light text on dark backgrounds. The perceived weight is lighter, so text needs more breathing room. Add 0.05-0.1 to your normal line-height.
+
+## Font Selection & Pairing
+
+### Choosing Distinctive Fonts
+
+**Avoid the invisible defaults**: Inter, Roboto, Open Sans, Lato, Montserrat. These are everywhere, making your design feel generic. They're fine for documentation or tools where personality isn't the goal—but if you want distinctive design, look elsewhere.
+
+**Better Google Fonts alternatives**:
+- Instead of Inter → **Instrument Sans**, **Plus Jakarta Sans**, **Outfit**
+- Instead of Roboto → **Onest**, **Figtree**, **Urbanist**
+- Instead of Open Sans → **Source Sans 3**, **Nunito Sans**, **DM Sans**
+- For editorial/premium feel → **Fraunces**, **Newsreader**, **Lora**
+
+**System fonts are underrated**: `-apple-system, BlinkMacSystemFont, "Segoe UI", system-ui` looks native, loads instantly, and is highly readable. Consider this for apps where performance > personality.
+
+### Pairing Principles
+
+**The non-obvious truth**: You often don't need a second font. One well-chosen font family in multiple weights creates cleaner hierarchy than two competing typefaces. Only add a second font when you need genuine contrast (e.g., display headlines + body serif).
+
+When pairing, contrast on multiple axes:
+- Serif + Sans (structure contrast)
+- Geometric + Humanist (personality contrast)
+- Condensed display + Wide body (proportion contrast)
+
+**Never pair fonts that are similar but not identical** (e.g., two geometric sans-serifs). They create visual tension without clear hierarchy.
+
+### Web Font Loading
+
+The layout shift problem: fonts load late, text reflows, and users see content jump. Here's the fix:
+
+```css
+/* 1. Use font-display: swap for visibility */
+@font-face {
+  font-family: 'CustomFont';
+  src: url('font.woff2') format('woff2');
+  font-display: swap;
+}
+
+/* 2. Match fallback metrics to minimize shift */
+@font-face {
+  font-family: 'CustomFont-Fallback';
+  src: local('Arial');
+  size-adjust: 105%;        /* Scale to match x-height */
+  ascent-override: 90%;     /* Match ascender height */
+  descent-override: 20%;    /* Match descender depth */
+  line-gap-override: 10%;   /* Match line spacing */
+}
+
+body {
+  font-family: 'CustomFont', 'CustomFont-Fallback', sans-serif;
+}
+```
+
+Tools like [Fontaine](https://github.com/unjs/fontaine) calculate these overrides automatically.
+
+## Modern Web Typography
+
+### Fluid Type
+
+Use `clamp(min, preferred, max)` for fluid typography. The middle value (e.g., `5vw + 1rem`) controls scaling rate—higher vw = faster scaling. Add a rem offset so it doesn't collapse to 0 on small screens.
+
+**When NOT to use fluid type**: Button text, labels, UI elements (should be consistent), very short text, or when you need precise breakpoint control.
+
+### OpenType Features
+
+Most developers don't know these exist. Use them for polish:
+
+```css
+/* Tabular numbers for data alignment */
+.data-table { font-variant-numeric: tabular-nums; }
+
+/* Proper fractions */
+.recipe-amount { font-variant-numeric: diagonal-fractions; }
+
+/* Small caps for abbreviations */
+abbr { font-variant-caps: all-small-caps; }
+
+/* Disable ligatures in code */
+code { font-variant-ligatures: none; }
+
+/* Enable kerning (usually on by default, but be explicit) */
+body { font-kerning: normal; }
+```
+
+Check what features your font supports at [Wakamai Fondue](https://wakamaifondue.com/).
+
+## Typography System Architecture
+
+Name tokens semantically (`--text-body`, `--text-heading`), not by value (`--font-size-16`). Include font stacks, size scale, weights, line-heights, and letter-spacing in your token system.
+
+## Accessibility Considerations
+
+Beyond contrast ratios (which are well-documented), consider:
+
+- **Never disable zoom**: `user-scalable=no` breaks accessibility. If your layout breaks at 200% zoom, fix the layout.
+- **Use rem/em for font sizes**: This respects user browser settings. Never `px` for body text.
+- **Minimum 16px body text**: Smaller than this strains eyes and fails WCAG on mobile.
+- **Adequate touch targets**: Text links need padding or line-height that creates 44px+ tap targets.
+
+---
+
+**Avoid**: More than 2-3 font families per project. Skipping fallback font definitions. Ignoring font loading performance (FOUT/FOIT). Using decorative fonts for body text.