substack-ui-skills

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Substack's UI design system. Use when building interfaces inspired by Substack's aesthetic - light mode, Inter font, 4px grid.

설치 방법

프로젝트 폴더에서 아래 명령어를 실행하고, 설치할 에이전트를 선택하세요.

설치 명령을 직접 실행해야 적용됩니다. 지원 에이전트와 필요한 권한·라이선스는 제작자의 안내를 확인하세요.

스킬 원문 파일

{
  "version": "1.0.0",
  "organization": "Substack",
  "source": "https://substack.com",
  "extracted": "2026-02-04",
  "categories": [
    "ui-design",
    "light-mode"
  ],
  "tokens": {
    "colors": 8,
    "typography": 42,
    "spacing": 0,
    "borders": 8
  }
}

---
name: substack-ui-skills
description: Substack's UI design system. Use when building interfaces inspired by Substack's aesthetic - light mode, Inter font, 4px grid.
license: MIT
metadata:
  author: design-skills
  version: "1.0.0"
  source: https://substack.com
---

# Substack UI Skills

Opinionated constraints for building Substack-style interfaces with AI agents.

## When to Apply

Reference these guidelines when:
- Building light-mode interfaces
- Creating Substack-inspired design systems
- Implementing UIs with Inter font and 4px grid

## Colors

- SHOULD use light backgrounds for primary surfaces
- MUST use `#FFFFFF` as page background (`surface-base`)
- SHOULD reduce color palette (currently 15 colors detected)
- MUST maintain text contrast ratio of at least 4.5:1 for accessibility

### Semantic Tokens

| Token | HEX | RGB | Usage |
|-------|-----|-----|-------|
| `surface-base` | #FFFFFF | rgb(255,255,255) | Page background |
| `surface-raised` | #FC5013 | rgb(252,80,19) | Cards, modals, raised surfaces |
| `surface-overlay` | #E9E9E9 | rgb(233,233,233) | Overlays, tooltips, dropdowns |
| `text-primary` | #999999 | rgb(153,153,153) | Headings, body text |
| `text-2` | #515151 | rgb(81,81,81) | Additional text |
| `text-secondary` | #717171 | rgb(113,113,113) | Secondary, muted text |
| `border-default` | #E7E7E7 | rgb(231,231,231) | Subtle borders, dividers |
| `destructive` | #E26739 | rgb(226,103,57) | Error states, delete actions |

## Typography

- MUST use `Inter` as primary font family
- SHOULD use single font family for consistency
- MUST use `36px` / `semi_bold` for primary headings
- MUST use `17px` / `500` for body text
- SHOULD reduce font weights (currently 4 detected)
- MUST use `text-balance` for headings and `text-pretty` for body text
- SHOULD use `tabular-nums` for numeric data
- NEVER modify letter-spacing unless explicitly requested

### Text Styles

| Style | Font | Size | Weight | Color | Count |
|-------|------|------|--------|-------|-------|
| `heading-1` | Inter | 36px | semi_bold | #BCDBD7 | 1 |
| `text-19px` | Inter | 19px | semi_bold | #4C4D4D | 1 |
| `body` | Inter | 17px | 500 | #535353 | 1 |
| `body-secondary` | Inter | 16px | 400 | #717171 | 1 |
| `body-secondary` | Inter | 16px | 400 | #6E6E6F | 1 |
| `body-secondary` | Inter | 16px | 400 | #F5C0A3 | 1 |
| `body-secondary` | Inter | 15px | 400 | #969696 | 2 |
| `body-secondary` | Inter | 15px | 500 | #515151 | 1 |
| `body-secondary` | Inter | 15px | 400 | #6F6F6F | 1 |
| `body-secondary` | Inter | 15px | 500 | #5D5D5D | 1 |

### Typography Reference

**Font Families:**
- `Inter` (used 43x)

**Font Sizes:** 5px, 9px, 10px, 11px, 12px, 13px, 14px, 15px, 16px, 17px, 19px, 36px

## Spacing

- MUST use 4px grid for spacing
- SHOULD use spacing from scale: 1px, 3px, 4px, 5px, 8px, 9px, 10px, 13px
- SHOULD use 4px as default gap between elements
- NEVER use arbitrary spacing values (use design scale)
- SHOULD maintain consistent padding within containers

## Borders

- MUST use border-radius from scale: 3px, 4px, 6px, 7px, 8px, 9px, 16px, 18px
- MUST use 1px border width consistently
- SHOULD use 9px as default border-radius
- NEVER use arbitrary border-radius values (use design scale)
- SHOULD use subtle borders (1px) for element separation

### Border Radius Reference

**Scale:** 3px, 4px, 6px, 7px, 8px, 9px, 16px, 18px

## Layout

- MUST design for 1920px base viewport width
- SHOULD use consistent element widths: 12px, 16px, 18px, 17px, 22px
- SHOULD maintain text-heavy layout with clear hierarchy
- NEVER use `h-screen`, use `h-dvh` for full viewport height
- MUST respect `safe-area-inset` for fixed elements
- SHOULD use `size-*` for square elements instead of `w-*` + `h-*`

### Detected Layout Patterns

- **Main Content**: width: 1920px, height: 1080px

## Components

- MUST use `0px` height for input fields

### Buttons

| Variant | Background | Text | Border | Height | Radius |
|---------|------------|------|--------|--------|--------|
| Ghost | transparent | #515151 | none | - | - |

### Inputs

- Height: `0px`

## Interactive States

### Focus

- MUST use `2px` outline with accent color (`#5E6AD2`)
- MUST use `2px` outline-offset
- NEVER remove focus indicators

### Hover

- Buttons (primary): lighten background by 10%
- Buttons (secondary): use `#FC5013` background
- List items: use `#FC5013` background

### Disabled

- MUST use `opacity: 0.5`
- MUST use `cursor: not-allowed`

## Interaction

- MUST use an `AlertDialog` for destructive or irreversible actions
- SHOULD use structural skeletons for loading states
- MUST show errors next to where the action happens
- NEVER block paste in `input` or `textarea` elements
- MUST add an `aria-label` to icon-only buttons

## Animation

- NEVER add animation unless it is explicitly requested
- MUST animate only compositor props (`transform`, `opacity`)
- NEVER animate layout properties (`width`, `height`, `top`, `left`, `margin`, `padding`)
- SHOULD use `ease-out` on entrance animations
- NEVER exceed `200ms` for interaction feedback
- SHOULD respect `prefers-reduced-motion`

## Performance

- NEVER animate large `blur()` or `backdrop-filter` surfaces
- NEVER apply `will-change` outside an active animation
- NEVER use `useEffect` for anything that can be expressed as render logic