# Typography Systems Reference
## Type Scale Construction
### Modular Scale
A modular scale creates harmonious relationships between font sizes using a mathematical ratio.
```tsx
// Common ratios
const RATIOS = {
minorSecond: 1.067, // 16:15
majorSecond: 1.125, // 9:8
minorThird: 1.2, // 6:5
majorThird: 1.25, // 5:4
perfectFourth: 1.333, // 4:3
augmentedFourth: 1.414, // √2
perfectFifth: 1.5, // 3:2
goldenRatio: 1.618, // φ
};
function generateScale(baseSize: number, ratio: number, steps: number): number[] {
const scale: number[] = [];
for (let i = -2; i <= steps; i++) {
scale.push(Math.round(baseSize * Math.pow(ratio, i) * 100) / 100);
}
return scale;
}
// Generate a scale with 16px base and perfect fourth ratio
const typeScale = generateScale(16, RATIOS.perfectFourth, 6);
// Result: [9, 12, 16, 21.33, 28.43, 37.9, 50.52, 67.34, 89.76]
```
### CSS Custom Properties
```css
:root {
/* Base scale using perfect fourth (1.333) */
--font-size-2xs: 0.563rem; /* ~9px */
--font-size-xs: 0.75rem; /* 12px */
--font-size-sm: 0.875rem; /* 14px */
--font-size-base: 1rem; /* 16px */
--font-size-md: 1.125rem; /* 18px */
--font-size-lg: 1.333rem; /* ~21px */
--font-size-xl: 1.5rem; /* 24px */
--font-size-2xl: 1.777rem; /* ~28px */
--font-size-3xl: 2.369rem; /* ~38px */
--font-size-4xl: 3.157rem; /* ~50px */
--font-size-5xl: 4.209rem; /* ~67px */
/* Font weights */
--font-weight-normal: 400;
--font-weight-medium: 500;
--font-weight-semibold: 600;
--font-weight-bold: 700;
/* Line heights */
--line-height-tight: 1.1;
--line-height-snug: 1.25;
--line-height-normal: 1.5;
--line-height-relaxed: 1.625;
--line-height-loose: 2;
/* Letter spacing */
--letter-spacing-tighter: -0.05em;
--letter-spacing-tight: -0.025em;
--letter-spacing-normal: 0;
--letter-spacing-wide: 0.025em;
--letter-spacing-wider: 0.05em;
--letter-spacing-widest: 0.1em;
}
```
## Font Loading Strategies
### FOUT Prevention
```css
/* Use font-display to control loading behavior */
@font-face {
font-family: 'Inter';
src: url('/fonts/Inter-Variable.woff2') format('woff2-variations');
font-weight: 100 900;
font-style: normal;
font-display: swap; /* Show fallback immediately, swap when loaded */
}
/* Optional: size-adjust for better fallback matching */
@font-face {
font-family: 'Inter Fallback';
src: local('Arial');
size-adjust: 107%; /* Adjust to match Inter metrics */
ascent-override: 90%;
descent-override: 22%;
line-gap-override: 0%;
}
body {
font-family: 'Inter', 'Inter Fallback', system-ui, sans-serif;
}
```
### Preloading Critical Fonts
```html
```
### Variable Fonts
```css
/* Variable font with weight and width axes */
@font-face {
font-family: 'Inter';
src: url('/fonts/Inter-Variable.woff2') format('woff2');
font-weight: 100 900;
font-stretch: 75% 125%;
}
/* Use font-variation-settings for fine control */
.custom-weight {
font-variation-settings: 'wght' 450, 'wdth' 95;
}
/* Or use standard properties */
.semi-expanded {
font-weight: 550;
font-stretch: 110%;
}
```
## Responsive Typography
### Fluid Type Scale
```css
/* Using clamp() for responsive sizing */
h1 {
/* min: 32px, preferred: 5vw + 16px, max: 64px */
font-size: clamp(2rem, 5vw + 1rem, 4rem);
line-height: 1.1;
}
h2 {
font-size: clamp(1.5rem, 3vw + 0.5rem, 2.5rem);
line-height: 1.2;
}
p {
font-size: clamp(1rem, 1vw + 0.75rem, 1.25rem);
line-height: 1.6;
}
/* Fluid line height */
.fluid-text {
--min-line-height: 1.3;
--max-line-height: 1.6;
--min-vw: 320;
--max-vw: 1200;
line-height: calc(
var(--min-line-height) +
(var(--max-line-height) - var(--min-line-height)) *
((100vw - var(--min-vw) * 1px) / (var(--max-vw) - var(--min-vw)))
);
}
```
### Viewport-Based Scaling
```tsx
// Tailwind config for responsive type
module.exports = {
theme: {
fontSize: {
xs: ['0.75rem', { lineHeight: '1rem' }],
sm: ['0.875rem', { lineHeight: '1.25rem' }],
base: ['1rem', { lineHeight: '1.5rem' }],
lg: ['1.125rem', { lineHeight: '1.75rem' }],
xl: ['1.25rem', { lineHeight: '1.75rem' }],
'2xl': ['1.5rem', { lineHeight: '2rem' }],
'3xl': ['1.875rem', { lineHeight: '2.25rem' }],
'4xl': ['2.25rem', { lineHeight: '2.5rem' }],
'5xl': ['3rem', { lineHeight: '1' }],
},
},
};
// Component with responsive classes
function Heading({ children }) {
return (
{children}
);
}
```
## Readability Guidelines
### Optimal Line Length
```css
/* Optimal reading width: 45-75 characters */
.prose {
max-width: 65ch; /* ~65 characters */
}
/* Narrower for callouts */
.callout {
max-width: 50ch;
}
/* Wider for code blocks */
pre {
max-width: 80ch;
}
```
### Vertical Rhythm
```css
/* Establish baseline grid */
:root {
--baseline: 1.5rem; /* 24px at 16px base */
}
/* All margins should be multiples of baseline */
h1 {
font-size: 2.5rem;
line-height: calc(var(--baseline) * 2);
margin-top: calc(var(--baseline) * 2);
margin-bottom: var(--baseline);
}
h2 {
font-size: 2rem;
line-height: calc(var(--baseline) * 1.5);
margin-top: calc(var(--baseline) * 1.5);
margin-bottom: calc(var(--baseline) * 0.5);
}
p {
font-size: 1rem;
line-height: var(--baseline);
margin-bottom: var(--baseline);
}
```
### Text Wrapping
```css
/* Prevent orphans and widows */
p {
text-wrap: pretty; /* Experimental: improves line breaks */
widows: 3;
orphans: 3;
}
/* Balance headings */
h1, h2, h3 {
text-wrap: balance;
}
/* Prevent breaking in specific elements */
.no-wrap {
white-space: nowrap;
}
/* Hyphenation for justified text */
.justified {
text-align: justify;
hyphens: auto;
-webkit-hyphens: auto;
}
```
## Font Pairing Guidelines
### Contrast Pairings
```css
/* Serif heading + Sans body */
:root {
--font-heading: 'Playfair Display', Georgia, serif;
--font-body: 'Source Sans Pro', -apple-system, sans-serif;
}
/* Geometric heading + Humanist body */
:root {
--font-heading: 'Space Grotesk', sans-serif;
--font-body: 'IBM Plex Sans', sans-serif;
}
/* Modern sans heading + Classic serif body */
:root {
--font-heading: 'Inter', system-ui, sans-serif;
--font-body: 'Georgia', Times, serif;
}
```
### Superfamily Approach
```css
/* Single variable font family for all uses */
:root {
--font-family: 'Inter', system-ui, sans-serif;
}
h1 {
font-family: var(--font-family);
font-weight: 800;
letter-spacing: -0.02em;
}
p {
font-family: var(--font-family);
font-weight: 400;
letter-spacing: 0;
}
.caption {
font-family: var(--font-family);
font-weight: 500;
font-size: 0.875rem;
text-transform: uppercase;
letter-spacing: 0.05em;
}
```
## Semantic Typography Classes
```css
/* Text styles by purpose, not appearance */
.text-display {
font-size: var(--font-size-5xl);
font-weight: var(--font-weight-bold);
line-height: var(--line-height-tight);
letter-spacing: var(--letter-spacing-tight);
}
.text-headline {
font-size: var(--font-size-3xl);
font-weight: var(--font-weight-semibold);
line-height: var(--line-height-snug);
}
.text-title {
font-size: var(--font-size-xl);
font-weight: var(--font-weight-semibold);
line-height: var(--line-height-snug);
}
.text-body {
font-size: var(--font-size-base);
font-weight: var(--font-weight-normal);
line-height: var(--line-height-normal);
}
.text-body-sm {
font-size: var(--font-size-sm);
font-weight: var(--font-weight-normal);
line-height: var(--line-height-normal);
}
.text-caption {
font-size: var(--font-size-xs);
font-weight: var(--font-weight-medium);
line-height: var(--line-height-normal);
text-transform: uppercase;
letter-spacing: var(--letter-spacing-wide);
}
.text-overline {
font-size: var(--font-size-2xs);
font-weight: var(--font-weight-semibold);
line-height: var(--line-height-normal);
text-transform: uppercase;
letter-spacing: var(--letter-spacing-widest);
}
```
## OpenType Features
```css
/* Enable advanced typography features */
.fancy-text {
/* Small caps */
font-variant-caps: small-caps;
/* Ligatures */
font-variant-ligatures: common-ligatures;
/* Numeric features */
font-variant-numeric: tabular-nums lining-nums;
/* Fractions */
font-feature-settings: 'frac' 1;
}
/* Tabular numbers for aligned columns */
.data-table td {
font-variant-numeric: tabular-nums;
}
/* Old-style figures for body text */
.prose {
font-variant-numeric: oldstyle-nums;
}
/* Discretionary ligatures for headings */
.fancy-heading {
font-variant-ligatures: discretionary-ligatures;
}
```