<!-- SPDX-License-Identifier: MIT -->
<!-- SPDX-FileCopyrightText: 2025-2026 Marcus Quinn -->

# Design System: Notion — Typography Rules

## Font Family

- **Primary**: `NotionInter`, with fallbacks: `Inter, -apple-system, system-ui, Segoe UI, Helvetica, Apple Color Emoji, Arial, Segoe UI Emoji, Segoe UI Symbol`
- **OpenType Features**: `"lnum"` (lining numerals) and `"locl"` (localized forms) enabled on display and heading text.

## Hierarchy

| Role | Font | Size | Weight | Line Height | Letter Spacing | Notes |
|------|------|------|--------|-------------|----------------|-------|
| Display Hero | NotionInter | 64px (4.00rem) | 700 | 1.00 (tight) | -2.125px | Maximum compression, billboard headlines |
| Display Secondary | NotionInter | 54px (3.38rem) | 700 | 1.04 (tight) | -1.875px | Secondary hero, feature headlines |
| Section Heading | NotionInter | 48px (3.00rem) | 700 | 1.00 (tight) | -1.5px | Feature section titles, with `"lnum"` |
| Sub-heading Large | NotionInter | 40px (2.50rem) | 700 | 1.50 | normal | Card headings, feature sub-sections |
| Sub-heading | NotionInter | 26px (1.63rem) | 700 | 1.23 (tight) | -0.625px | Section sub-titles, content headers |
| Card Title | NotionInter | 22px (1.38rem) | 700 | 1.27 (tight) | -0.25px | Feature cards, list titles |
| Body Large | NotionInter | 20px (1.25rem) | 600 | 1.40 | -0.125px | Introductions, feature descriptions |
| Body | NotionInter | 16px (1.00rem) | 400 | 1.50 | normal | Standard reading text |
| Body Medium | NotionInter | 16px (1.00rem) | 500 | 1.50 | normal | Navigation, emphasized UI text |
| Body Semibold | NotionInter | 16px (1.00rem) | 600 | 1.50 | normal | Strong labels, active states |
| Body Bold | NotionInter | 16px (1.00rem) | 700 | 1.50 | normal | Headlines at body size |
| Nav / Button | NotionInter | 15px (0.94rem) | 600 | 1.33 | normal | Navigation links, button text |
| Caption | NotionInter | 14px (0.88rem) | 500 | 1.43 | normal | Metadata, secondary labels |
| Caption Light | NotionInter | 14px (0.88rem) | 400 | 1.43 | normal | Body captions, descriptions |
| Badge | NotionInter | 12px (0.75rem) | 600 | 1.33 | 0.125px | Pill badges, tags, status labels |
| Micro Label | NotionInter | 12px (0.75rem) | 400 | 1.33 | 0.125px | Small metadata, timestamps |

## Principles

- **Compression at scale**: NotionInter at display sizes uses -2.125px letter-spacing at 64px, progressively relaxing to -0.625px at 26px and normal at 16px. The compression creates density at headlines while maintaining readability at body sizes.
- **Four-weight system**: 400 (body/reading), 500 (UI/interactive), 600 (emphasis/navigation), 700 (headings/display). The broader weight range compared to most systems allows nuanced hierarchy.
- **Warm scaling**: Line height tightens as size increases -- 1.50 at body (16px), 1.23-1.27 at sub-headings, 1.00-1.04 at display. This creates denser, more impactful headlines.
- **Badge micro-tracking**: The 12px badge text uses positive letter-spacing (0.125px) -- the only positive tracking in the system, creating wider, more legible small text.
