---
version: alpha
name: Y Combinator
description: Light design system extracted from www.ycombinator.com (DOM-true values, Emblematic extractor 0.2.0, 2026-11-12).
colors:
  background: "#F5F5EE"
  on-surface: "#16140F"
  primary: "#000000"
  white: "#FFFFFF"
  color-5: "#0000001A"
  color-6: "#00000080"
  color-7: "#000000B3"
  color-8: "#00000066"
  on-primary: "#FFFFFF"
typography:
  display-lg:
    fontFamily: Source Serif 4
    fontSize: 84px
    fontWeight: 400
    lineHeight: 1.1
  headline-md:
    fontFamily: Source Serif 4
    fontSize: 48px
    fontWeight: 400
    lineHeight: 1.2
  title-md:
    fontFamily: Avenir Light
    fontSize: 14px
    fontWeight: 300
    lineHeight: 1.3
  body-md:
    fontFamily: Avenir Light
    fontSize: 16px
    fontWeight: 300
    lineHeight: 1.375
rounded:
  full: 9999px
spacing:
  xxs: 4px
  xs: 6px
  sm: 8px
  md: 12px
  lg: 16px
  xl: 20px
  2xl: 24px
  3xl: 32px
  4xl: 40px
  5xl: 60px
  6xl: 80px
  7xl: 120px
  8xl: 170px
  base: 4px
  container: 1100px
components:
  button-primary:
    backgroundColor: "{colors.primary}"
    textColor: "{colors.white}"
    rounded: "{rounded.full}"
    padding: 0px
    height: 40px
---

# Y Combinator

> Extracted from [https://www.ycombinator.com/](https://www.ycombinator.com/) on 2026-11-12 by Emblematic. Every value below was read from the rendered DOM (computed styles, `document.fonts`, and the fonts Chrome actually used to paint text), not estimated from pixels. When the YAML front matter and this prose disagree, the YAML wins. Copy values from this file exactly; don't transcribe them from memory. Don't copy logos, imagery, illustrations or marketing copy.

## Overview

Y Combinator uses a light canvas (#F5F5EE) with a monochrome palette led by #000000. Type is set in **Source Serif 4** (display), **Avenir Light**, with 16px body text. Layout: 1100px container, top-sticky navigation, 7 sections. Built with react, tailwind, posthog, google-tag-manager, cloudflare.

## Colors

Area-weighted from painted backgrounds, text and borders on the 1440px light capture. Roles are inferred from usage (largest background, most text, interactive fills). Every hex is an exact computed value; a role marked *unverified* is a best guess that has not passed review, so its canonical token (e.g. `primary`) is left out of the front matter.

| Token | Hex | OKLCH | Role | Share of paint | CSS variable |
|---|---|---|---|---|---|
| `background` | `#F5F5EE` | 0.968 0.009 106.6 | bg | 83.7% | — |
| `on-surface` | `#16140F` | 0.192 0.01 88.8 | text | 4.7% | — |
| `primary` | `#000000` | 0 0 0 | accent | 4.3% | `--color-black` |
| `white` | `#FFFFFF` | 1 0 0 | other | 2.8% | `--color-white` |
| `color-5` | `#0000001A` (on bg `#DDDDD6`) | 0 0 0 | other | 1.1% | — |
| `color-6` | `#00000080` (on bg `#7B7B77`) | 0 0 0 | other | 1.1% | — |
| `color-7` | `#000000B3` (on bg `#4A4A47`) | 0 0 0 | other | 1.1% | — |
| `color-8` | `#00000066` (on bg `#93938F`) | 0 0 0 | other | 0.96% | — |

Contrast: text on background 16.81:1, accent 19.18:1.

Gradients in use: `linear-gradient(rgba(0, 0, 0, 0) 0%, rgba(0, 0, 0, 0) 40%, rgba(0, 0, 0, 0.1) 60%, rgba(0, 0, 0, 0.5) 85%, rgba(0, 0, 0, 0.7) 100%)`.

The site does not change under `prefers-color-scheme: dark`.

## Typography

| Family | Role | Weights | Share of text | Source |
|---|---|---|---|---|
| **Source Serif 4** | display | 400 | 51.3% | webfont |
| **Avenir Light** (CSS: `Avenir`) | body | 300 | 42.4% | system (stack `Avenir, ui-sans-serif, system-ui, sans-serif, "Apple Color E`, resolved on macos) |
| **Avenir Book** (CSS: `Avenir`) | other | 400 | 5.9% | system (stack `Avenir, ui-sans-serif, system-ui, sans-serif, "Apple Color E`, resolved on macos) |

Declared in `@font-face` but not used to paint text on this page: Outfit, KaTeX Main, KaTeX SansSerif, DM Sans, KaTeX Fraktur, KaTeX Math. Don't treat these as the page's fonts.

Scale (px): 11, 14, 16, 18, 19, 20, 22, 32, 48, 60, 84. Effective ratio ≈ 1.23 (close to a major third). Body 16px at line-height 1.375; display 84px with tracking 0em. Headings are title case. On a 390px viewport the body is 19px and display 32px.

## Layout

Spacing follows a 4px base unit; the most used steps are 4, 6, 8, 12, 16, 20, 24, 32, 40, 60, 80, 120, 170px. Sections open with about 215px of space before their first line of text. Content sits in a 1100px container on a 3-column grid. Text density 0.086 (text area / page area).

Section order (desktop). Kinds below the review threshold are shown as *section*:

1. **nav** (64px, bg #F5F5EE)
2. **hero** (810px, bg #F5F5EE)
3. **section** (1892px, bg #F5F5EE)
4. **section** — “In Founders’ Words” (2467px, bg #F5F5EE)
5. **testimonials** (4307px, bg #F5F5EE)
6. **section** — “How To Build The Future: Paul Graham & Amjad Masad” (1673px, bg #F5F5EE)
7. **footer** — “Company” (525px, bg #000000)

## Shapes

Dominant corner radius 0px; radii in use: pill. Borders: hairline (1px).

## Components

- **button-primary**: backgroundColor `#000000`, textColor `#FFFFFF`, rounded `9999px`, padding `0px 20px`, height `40px`, fontFamily `Source Serif 4`, fontSize `14px`, fontWeight `400` (e.g. “Apply”)

## Do's and Don'ts

- Do reserve `#000000` for primary actions and highlights; it covers only 4.3% of the painted page.
- Do keep the palette monochrome; there is no chromatic brand accent on the page.
- Do set body copy in Avenir Light at 16px / 1.375.
- Do use Source Serif 4 only for display sizes, not for body text.
- Don't introduce font weights beyond 300, 400.
- Don't add drop shadows; depth comes from tone and borders.
- Do keep corners at 0px for most controls.
- Do snap spacing to multiples of 4px.
- Don't copy this site's logos, illustrations, photography or copy; use the system, not the brand assets.

## Provenance

Spec v2, extractor 0.2.0. Render quality: **ok**. Vision pass: not run. Fields below confidence 0.7 are hedged or left out above: `layout.columns`, `layout.hero`, `layout.section_count`, `sections[].kind`, `space.section_padding_px`. Full per-field provenance is in `spec.json`.