# DESIGN.md: Heroku-style design system

Measured from https://www.heroku.com/ on 2026-10-15 by PikSpec (https://www.pikspec.com). An independent measurement of the rendered page, not Heroku's official design system, and not affiliated with Heroku.

Use it to build your own product in this design language: put this file in your project root and tell your AI tool (Claude Code, Cursor, Codex, Lovable, v0) to follow DESIGN.md. Never use the original's name, logo, copy or images; licensed fonts are replaced with the closest free Google Fonts.

To capture any other page, or get a ready project for your tool: https://www.pikspec.com/build-with-ai

HOW IT SHOULD LOOK
Build it in the design language of heroku.com, measured from the live site: it should feel designed by the same team as heroku.com — the same temperament, colour, type and density — for a different product. Never use heroku.com's name, logo, words or images.

Stack: use the one your project already has. Starting fresh: React + Vite + TypeScript + Tailwind CSS v4, with no UI kit (no shadcn/ui, MUI or Chakra) — their defaults would override this system. In a chat that shows one file (an artifact or canvas), build one HTML file instead, with the tokens below in its <style> block.
Use every value exactly as written. Do not round, rename, approximate or substitute a colour, size, radius, shadow or easing (fonts: see section 1). Anything not listed here does not exist in this system.

THE WEBSITE THIS SYSTEM COMES FROM
- Reference page: https://www.heroku.com/ — "www.heroku.com" (home page).
- Page frame: a top navigation bar and a footer.
- Content is grouped in cards (1 on the page). Keep cards for grouped content only, not for every section.
- It uses 111 images, 3 of them large. Large, real product imagery is part of the look — leave clearly labelled image slots at those sizes rather than stock photos or abstract 3D shapes.
- Interaction: 20 buttons on one page.
- The page runs about 8 screens long at 1440px wide.
- Density is moderate.

HOW IT LOOKS (WHAT MAKES IT LOOK LIKE ITSELF, BEYOND THE VALUES)
- Almost entirely neutral: 97% of the page is painted in #FFFFFF and #F9F9FB.
- #300B60 is an accent: 1.5% of the page, used for text only. Don't fill large areas with it.
- #0176D3 is an accent: 1.3% of the page, used for backgrounds and text and small fills such as buttons. Don't fill large areas with it.
- The largest type (40px Avant Garde) is semibold (600).
- Balanced: text covers 16% of the page.
- Share of the painted page: #FFFFFF 81.1% (dominant, backgrounds); #F9F9FB 7.1% (supporting, backgrounds); #EEF1F6 3.8% (detail, backgrounds); #181818 3% (supporting, text); #300B60 1.5% (accent, text); #0176D3 1.3% (accent, backgrounds and text); #F7F6F8 1.1% (detail, backgrounds); #240643 0.5% (accent, text). Keep accents at these proportions; do not promote them to fills.
- Hairline dividers: 1px lines in #E2E8F0 separate sections and rows (4 of them).
- Type as set (size, weight and tracking measured together; use these pairs): 40px weight 600; 32px weight 600; 25px weight 400; 24px weight 700; 20px weight 400; 18px weight 400 tracking -0.003em.

1. DESIGN TOKENS — PASTE INTO YOUR GLOBAL CSS
Allowed colours, with how the original uses each. Use no other colour, including in hover states:
- #FFFFFF — 81.1% · backgrounds (var(--color-background))
- #F9F9FB — 7.1% · backgrounds (var(--color-f9f9fb))
- #EEF1F6 — 3.8% · backgrounds (var(--color-eef1f6))
- #181818 — 3% · text (var(--color-text))
- #300B60 — 1.5% · text
- #0176D3 — 1.3% · backgrounds, text (var(--color-action))
- #F7F6F8 — 1.1% · backgrounds (var(--color-f7f6f8))
- #240643 — 0.5% · text
- #333D47 — 0.4% · text (var(--color-text-muted))
- #211746 — 0.1% · text
- #E2E8F0 — hairlines and grid lines
- #DDDDDD — Surface (var(--color-surface))
Fonts — put these first in your global CSS (one import per font, so one that fails cannot stop the others):
```css
@import url("https://fonts.googleapis.com/css2?family=Figtree:wght@300;400;600;700&display=swap");
@import url("https://fonts.googleapis.com/css2?family=JetBrains+Mono:wght@400&display=swap");
```
Font: heroku.com uses Salesforce Sans (body), BentonSans (display), Avant Garde (interface) and SFMono-Regular (code) — its own licensed faces, not available to download. This kit uses Figtree for body, display and interface and JetBrains Mono for code, the closest free matches, already in the tokens. If you own the original, add it with @font-face and it is used first; to use another font, change the --font-* variables.
Keep every size, weight, line height and tracking exactly as listed whichever font renders.
```css
:root {
  --color-background: #FFFFFF; /* Background */
  --color-surface: #DDDDDD; /* Surface */
  --color-text: #181818; /* Text */
  --color-text-muted: #333D47; /* Text muted */
  --color-border: #DDDDDD; /* Border */
  --color-action: #0176D3; /* Action */
  --color-on-action: #FFFFFF; /* On action */
  --color-link: #0176D3; /* Link */
  --color-f9f9fb: #F9F9FB; /* 7.1% of the page, as fills */
  --color-eef1f6: #EEF1F6; /* 3.8% of the page, as fills */
  --color-f7f6f8: #F7F6F8; /* 1.1% of the page, as fills */
  --font-body: "Salesforce Sans", "Figtree", sans-serif; /* Salesforce Sans on the site; Figtree renders */
  --font-display: "BentonSans", "Figtree", sans-serif; /* BentonSans on the site; Figtree renders */
  --font-interface: "Avant Garde", "Figtree", sans-serif; /* Avant Garde on the site; Figtree renders */
  --font-code: "SFMono-Regular", "JetBrains Mono", monospace; /* SFMono-Regular on the site; JetBrains Mono renders */
  --type-display: 40px; /* Display, weight 600 */
  --type-display-leading: 48px;
  --type-headline-large: 32px; /* Headline Large, weight 600 */
  --type-headline-large-leading: 40px;
  --type-headline-medium: 25px; /* Headline Medium, weight 400 */
  --type-headline-medium-leading: 25px;
  --type-headline-small: 24px; /* Headline Small, weight 700 */
  --type-headline-small-leading: 32px;
  --type-title-large: 20px; /* Title Large, weight 400 */
  --type-title-large-leading: 30px;
  --type-title-small: 18px; /* Title Small, weight 400 */
  --type-title-small-leading: 25.2px;
  --type-title-small-tracking: -0.003em;
  --type-body-large: 16px; /* Body Large, weight 400 */
  --type-body-large-leading: 25.6px;
  --type-body-medium: 15px; /* Body Medium, weight 400 */
  --type-body-medium-leading: 20px;
  --type-body-small: 14px; /* Body Small, weight 400 */
  --type-body-small-leading: 22.4px;
  --type-label: 12px; /* Label, weight 700 */
  --type-label-leading: 18px;
  --type-label-tracking: 0.05em;
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;
  --space-10: 40px;
  --space-12: 48px;
  --space-14: 56px;
  --space-15: 60px;
  --space-18: 72px;
  --space-20: 80px;
  --space-25: 100px;
  --space-37: 148px;
  --radius-xs: 2px;
  --radius-sm: 3px;
  --radius-md: 4px;
  --radius-lg: 5px;
  --radius-2xl: 17px;
  --radius-3xl: 20px;
  --elevation-1: rgb(199, 197, 199) 0px 0px 12px 2px;
  --elevation-2: rgba(0, 0, 0, 0.1) 0px 10px 15px 0px, rgba(0, 0, 0, 0.05) 0px 4px 6px 0px;
  --duration-1: 0.1s;
  --duration-2: 0.3s;
  --duration-3: 0.4s;
}
```
Tailwind CSS v4 (the default for new projects): put this after `@import "tailwindcss";`. It removes Tailwind's own palette, so only these colours exist as utilities:
```css
@theme {
  --color-*: initial;
  --color-background: #FFFFFF;
  --color-surface: #DDDDDD;
  --color-text: #181818;
  --color-text-muted: #333D47;
  --color-border: #DDDDDD;
  --color-action: #0176D3;
  --color-on-action: #FFFFFF;
  --color-link: #0176D3;
  --color-f9f9fb: #F9F9FB;
  --color-eef1f6: #EEF1F6;
  --color-f7f6f8: #F7F6F8;
  --font-body: "Salesforce Sans", "Figtree", sans-serif;
  --font-display: "BentonSans", "Figtree", sans-serif;
  --font-interface: "Avant Garde", "Figtree", sans-serif;
  --font-code: "SFMono-Regular", "JetBrains Mono", monospace;
  --text-display: 40px;
  --text-display--line-height: 48px;
  --text-headline-large: 32px;
  --text-headline-large--line-height: 40px;
  --text-headline-medium: 25px;
  --text-headline-medium--line-height: 25px;
  --text-headline-small: 24px;
  --text-headline-small--line-height: 32px;
  --text-title-large: 20px;
  --text-title-large--line-height: 30px;
  --text-title-small: 18px;
  --text-title-small--line-height: 25.2px;
  --text-title-small--letter-spacing: -0.003em;
  --text-body-large: 16px;
  --text-body-large--line-height: 25.6px;
  --text-body-medium: 15px;
  --text-body-medium--line-height: 20px;
  --text-body-small: 14px;
  --text-body-small--line-height: 22.4px;
  --text-label: 12px;
  --text-label--line-height: 18px;
  --text-label--letter-spacing: 0.05em;
  --radius-xs: 2px;
  --radius-sm: 3px;
  --radius-md: 4px;
  --radius-lg: 5px;
  --radius-2xl: 17px;
  --radius-3xl: 20px;
  --shadow-e1: rgb(199, 197, 199) 0px 0px 12px 2px;
  --shadow-e2: rgba(0, 0, 0, 0.1) 0px 10px 15px 0px, rgba(0, 0, 0, 0.05) 0px 4px 6px 0px;
}
```
Tailwind CSS v3 only: extend the theme with these instead, and use no other palette:
```js
// tailwind.config — theme.extend
{
  colors: { "background": "var(--color-background)", "surface": "var(--color-surface)", "text": "var(--color-text)", "text-muted": "var(--color-text-muted)", "border": "var(--color-border)", "action": "var(--color-action)", "on-action": "var(--color-on-action)", "link": "var(--color-link)" },
  fontFamily: { "body": ["var(--font-body)"], "display": ["var(--font-display)"], "interface": ["var(--font-interface)"], "code": ["var(--font-code)"] },
  borderRadius: { "xs": "var(--radius-xs)", "sm": "var(--radius-sm)", "md": "var(--radius-md)", "lg": "var(--radius-lg)", "2xl": "var(--radius-2xl)", "3xl": "var(--radius-3xl)" },
  boxShadow: { "e1": "var(--elevation-1)", "e2": "var(--elevation-2)" },
}
```

2. BASE STYLES
```css
html { background: var(--color-background); }
body { margin: 0; font-family: var(--font-body); font-size: var(--type-body-large); line-height: var(--type-body-large-leading); color: var(--color-text); -webkit-font-smoothing: antialiased; -moz-osx-font-smoothing: grayscale; }
h1, h2, h3 { font-family: var(--font-display); margin: 0; }
a { color: var(--color-link); }
:focus-visible { outline: 2px solid var(--color-action); outline-offset: 2px; }
```

3. COMPONENTS — MATCH THESE EXACTLY
```css
.link { /* Inline */
  background: transparent;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: 10px 10px 10px 10px;
  color: var(--color-link);
  font-family: var(--font-body);
  font-size: var(--type-body-large);
  font-weight: 400;
  line-height: 25.6px;
  /* recorded states: focus-visible, hover, focus, active */
}
.link-2 { /* Inline 2 */
  background: transparent;
  color: var(--color-link);
  font-family: var(--font-body);
  font-size: var(--type-body-large);
  font-weight: 400;
  line-height: 25.6px;
  /* recorded states: focus-visible, hover, focus, active */
}
.link-3 { /* Strong */
  background: transparent;
  color: #240643;
  font-family: var(--font-body);
  font-size: var(--type-title-small);
  font-weight: 700;
  line-height: 23px;
  /* recorded states: focus-visible, hover, focus, active */
}
.nav-2 { /* Alternative 1 */
  background: transparent;
  font-family: var(--font-body);
  font-size: var(--type-body-large);
  font-weight: 400;
  line-height: 27.2px;
}
.nav-3 { /* Alternative 2 */
  background: transparent;
  min-height: 40px;
  color: #211746;
  font-family: var(--font-body);
  font-size: var(--type-body-large);
  font-weight: 400;
  line-height: 25px;
}
.card { /* Default */
  background: var(--color-background);
  border: 1px solid #E2E8F0;
  border-radius: var(--radius-lg);
  min-height: 300px;
  box-shadow: var(--elevation-2);
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--type-body-large);
  font-weight: 400;
  line-height: 25.6px;
}
.button { /* Primary */
  background: var(--color-action);
  border: 2px solid #0176D3;
  border-radius: var(--radius-md);
  padding: 12px 32px 12px 32px;
  min-height: 52px;
  color: var(--color-on-action);
  font-family: var(--font-body);
  font-size: var(--type-body-large);
  font-weight: 700;
  line-height: 24px;
  /* recorded states: focus-visible, hover, focus, active */
}
.button-2 { /* Secondary */
  background: var(--color-background);
  border-radius: var(--radius-md);
  padding: 12px 15px 12px 15px;
  min-height: 38px;
  color: var(--color-link);
  font-family: var(--font-body);
  font-size: var(--type-body-small);
  font-weight: 700;
  line-height: 14px;
  /* recorded states: focus-visible, hover, focus, active */
}
```
Where a component lists recorded states, write those states using only the colours above; the capture saw that the state exists, not its values. Never invent a state colour.

4. PAGE COMPOSITION
- Light interface on #FFFFFF. Keep that ground; do not add a dark mode.
- Sections change ground between Background (#FFFFFF), #F9F9FB and #EEF1F6; use only those.
- #0176D3 is the action colour. Fill the primary action with it and little else — at most one #0176D3-filled element per screen; other accents keep to the uses listed above.
- Type: Figtree (standing in for Salesforce Sans) for body; Figtree (standing in for BentonSans) for display; Figtree (standing in for Avant Garde) for interface; JetBrains Mono (standing in for SFMono-Regular) for code. Hierarchy comes from size and weight, not colour or decoration.
- Everything sits on a 4px grid.
- Corner radii are 2px, 3px, 4px, 5px, 17px, 20px — nothing else.
- Body text uses Salesforce Sans at around 16px, weights 400, 700.
- Headings use BentonSans; the largest heading is 42px.
- Primary buttons are #0176D3, 4px radius, weight 700.
- Cards use 5px corners with a soft shadow.
- Corner radii in use: 4px, 2px, 3px, 5px, 20px.

HOW THE ORIGINAL PACES ITS PAGE (BORROW THE RHYTHM — THE OPENING, THE COLOURED BANDS, THE CARD GRIDS — NOT THE LIST; BUILD THE SECTIONS YOUR PRODUCT NEEDS)
1. Hero — 518px tall, centred 40px heading (weight 600) set mid-band.
2. Grid — 1148px tall, 12 items in 3 columns with 50px gaps, centred 32px heading (weight 600), on #FFFFFF.
3. Statement — 518px tall, a strip of 9 small items (logos, links or icons), centred 32px heading (weight 600), on #F9F9FB.
4. Cards — 612px tall, 3 equal columns, 50px gap, centred 32px heading (weight 600), on #FFFFFF.
5. Grid — 596px tall, 7 items in 6 columns with 30px gaps, centred 32px heading (weight 600) set mid-band, on #EEF1F6.
6. Split — 474px tall, split 7 / 5, 50px gap, left-aligned 32px heading (weight 600), image on the left.
7. Cards — 302px tall, 6 equal columns, 30px gap, centred 32px heading (weight 600), on #FFFFFF.
8. Split — 517px tall, split 4 / 8, left-aligned 18px heading (weight 400), image on the left, on #FFFFFF.
9. Grid — 923px tall, 6 items in 3 columns with 50px gaps, centred 32px heading (weight 600) set mid-band, on #FFFFFF.
10. Cards — 619px tall, 3 equal columns, 30px gap, centred 32px heading (weight 700), on #F9F9FB.
11. Statement — 276px tall, centred 32px heading (weight 600).
12. Footer — 916px tall, split 3 / 3 / 2 / 2 / 2, 50px gap, left-aligned 18px heading (weight 700).
- Content sits in a 1200px container, 120px from the edge at 1440px wide.
- A 167px header scrolls away, transparent over the first section.
- The hero is 518px (0.6 screens): centred 40px heading (weight 600) set mid-band.
- Column splits on a 12-column grid: thirds (4×), sixths (2×), 7/5, 4/8; gaps of 50px.
- Headings are centred (9 of 12 sections).
- Sections change background 8 times, between #FFFFFF, #F9F9FB, #EEF1F6: colour comes in full-width bands; #FFFFFF is large rounded panels inside a section instead.
- A typical section is about 596px tall.

COPY SHAPE (MATCH THE LENGTH AND CASE; WRITE YOUR OWN WORDS)
- The main heading is 10 words long.
- Section headings are medium length: typically 4 words.
- Headings are in Title Case.
- The page describes itself in about 20 words; keep your intro paragraph to about that length.

5. MOTION
Interactive elements change colour, background, border and opacity with the measured timing. Animate nothing else.
```css
a, button, [role="button"], input { transition: color var(--duration-1) ease-out, background-color var(--duration-1) ease-out, border-color var(--duration-1) ease-out, opacity var(--duration-1) ease-out; }
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation-duration: 0.01ms !important; animation-iteration-count: 1 !important; transition-duration: 0.01ms !important; scroll-behavior: auto !important; }
}
```
No scroll-triggered fade-ins, parallax, typewriter text or bouncing elements.

6. RESPONSIVE
- The design was measured at 1440px wide. Lay it out for that width first, then let it reflow down to 360px.
- Content sits in a column at most 1296px wide, centred, with var(--space-4) (16px) side padding on small screens.
- The largest heading scales fluidly: font-size: clamp(24px, 2.8vw, 40px). Every other size stays fixed.
- Break on composition, not device names: a row of columns drops a column when any column would be narrower than 240px; side-by-side splits stack when either side would be narrower than 320px.
- Spacing steps never change between sizes; use smaller steps from the same list where space is tight.
- On touch screens, every link and button has a hit area of at least 44 × 44px without changing its drawn size.

7. ACCESSIBILITY
- Text pairs that pass for body copy: Text on Background (17.8:1), Text muted on Background (11.1:1), Action on Background (4.6:1), Link on Background (4.6:1), Text on Surface (13.1:1), Text muted on Surface (8.1:1) and On action on Action (4.6:1).
- Only for text 24px and up, or 18.66px bold: Action on Surface (3.4:1) and Link on Surface (3.4:1).
- Use no other text-on-background pairing.
- One h1 per page, headings in order, landmarks (header, nav, main, footer), real buttons and links, a label on every field, alt text on every image, an aria-label on icon-only buttons.
- Every interactive element shows the :focus-visible outline above.

8. DO NOT (THESE ARE WHAT MAKE AI-BUILT SITES LOOK GENERIC)
- Only the two shadows in the tokens, on the components that use them. (2 shadow values were measured; inventing softer ones changes the depth of the page.)
- No gradients: not in backgrounds, text, buttons or borders. (No gradient was measured.)
- Only these colours: #FFFFFF, #F9F9FB, #EEF1F6, #181818, #300B60, #0176D3, #F7F6F8, #240643, #333D47, #211746, #E2E8F0, #DDDDDD. No new tints, no Tailwind defaults (slate, indigo, violet). (They are every colour that covers a measurable part of the page, and the colours its lines and drawings use.)
- #300B60 only for text — never as a section background or a large panel. (It covers 1.5% of the page.)
- #0176D3 only for backgrounds and text and small fills such as buttons — never as a section background or a large panel. (It covers 1.3% of the page.)
- Only the fonts in the tokens: Figtree for body; Figtree for display; Figtree for interface; JetBrains Mono for code. No other typeface, and no Inter, Roboto or system UI font unless it is one of these. (The page is set in Salesforce Sans and Avant Garde and BentonSans; the tokens carry what stands in for them.)
- Headings and large text never heavier than weight 700. Do not make headlines bold to add emphasis. (Every size from 24px up is set at weight 700 or lighter.)
- No stock photography or AI-generated photos. (Photographs cover almost none of the page.)
- No icon above every feature, no emoji, no decorative blobs, sparkles or glows. (None of these is part of the captured design; they are a coding model's defaults.)
- Build the sections your product needs, not the original's list. Give each one this system's look: its kinds of section (hero, grid, statement, cards, split, footer), its colours, type, shapes and spacing. (The style carries to any kind of site; the original's page was for a different product.)
- No glassmorphism, backdrop blur, glowing orbs, noise blobs or neon outlines.
- No row of three identical feature cards as the default section. Vary the layout from section to section: a split, a list, a single large statement, a table.
- No centred-everything hero with a pill badge, a gradient headline and two buttons. Lead with the most specific thing about the product.
- No filler copy: no "Unlock your potential", "Revolutionize", "Seamless", "Elevate", "Supercharge", "Next-gen" or lorem ipsum. Write plain, specific sentences a real company would publish.
- No made-up statistics, testimonials or customer logos. Leave a clearly marked [content: …] slot instead.
- No radius larger than the largest one listed.
- Do not use heroku.com's name, logo, copy or images. This is its design system, not its content.

BEFORE YOU FINISH
- Search your code for every colour, font size, spacing value, radius, shadow and easing, and replace anything that is not a variable above.
- Check that no [content: …] slot has been filled with invented facts.
- Search your CSS for gradient(. There should be none.
- Every colour value in your CSS is one of the allowed colours. Nothing else, including in hover states.
- #300B60 covers about 1.5% of the page or less, as on the original.
- #0176D3 covers about 1.3% of the page or less, as on the original.
- No text 24px or larger has a font-weight above 700.
- Every section, including ones the original does not have, uses only this system's colours, type, shapes and spacing.
- Content sits in a 1200px container with 120px side margins at 1440px.
- There is no placeholder copy (lorem ipsum, "Feature one", "Your headline here"). Every word is real.
- Take a screenshot at 1440px and put it beside the original. List every difference in colour, weight, spacing, alignment and imagery, and fix each before finishing. Then check 390px wide: nothing scrolls sideways and no heading runs off the screen.