# DESIGN.md: Spline-style design system

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

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 spline.design, measured from the live site: it should feel designed by the same team as spline.design — the same temperament, colour, type and density — for a different product. Never use spline.design'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://spline.design/ — "spline.design" (home page).
- Page frame: a top navigation bar and a footer.
- Content is grouped in cards (39 on the page, up to 14 side by side). Keep cards for grouped content only, not for every section.
- It uses 75 images including 14 videos, 47 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: 19 buttons and 1 form field on one page.
- The page runs about 14 screens long at 1440px wide.
- Density is low: few elements per screen, generous space around each one.

HOW IT LOOKS (WHAT MAKES IT LOOK LIKE ITSELF, BEYOND THE VALUES)
- Almost entirely neutral: 99% of the page is painted in #000000 and #191A1D.
- #0062FF is an accent: 0.1% of the page, as small fills such as buttons and badges. Keep it to small areas.
- #CE9178 is an accent: under 0.1% of the page, used for text only. Don't fill large areas with it.
- The largest type (40px Spline Sans) is medium weight, not bold (500).
- Very airy: text covers 5% of the page. Sections sit about 548px apart.
- Structure comes from thin grid lines, not from shadows or filled cards.
- Share of the painted page: #000000 95.8% (dominant, backgrounds); #FFFFFF 2.3% (supporting, text); #191A1D 1.4% (detail, backgrounds); #3A3A3A 0.2% (detail, backgrounds); #1E1E23 0.2% (detail, backgrounds); #0062FF 0.1% (accent, backgrounds). Keep accents at these proportions; do not promote them to fills.
- Hairline grid: 1px lines in #FFFFFF run both across and down the page (21 across, 20 down), dividing it into cells instead of cards.
- Small marks: 14 small decorative marks (dots, crosses or ticks under 16px) in #FFFFFF, placed at corners and edges.
- Large images: Photographs, video or raster artwork cover about 23% of the page.
- Type as set (size, weight and tracking measured together; use these pairs): 40px weight 500; 38.4px weight 500; 36px weight 500; 24px weight 400; 20px weight 500; 18px weight 400.

1. DESIGN TOKENS — PASTE INTO YOUR GLOBAL CSS
Allowed colours, with how the original uses each. Use no other colour, including in hover states:
- #000000 — 95.8% · backgrounds (var(--color-background))
- #FFFFFF — 2.3% · text (var(--color-text))
- #191A1D — 1.4% · backgrounds (var(--color-surface))
- #3A3A3A — 0.2% · backgrounds
- #1E1E23 — 0.2% · backgrounds
- #0062FF — 0.1% · backgrounds
- #888888 — Text muted (var(--color-text-muted))
- #CE9178 — Warning (var(--color-warning))
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=Spline+Sans:wght@400;500&display=swap");
@import url("https://fonts.googleapis.com/css2?family=Spline+Sans+Mono:wght@400&display=swap");
```
Spline Sans and Spline Sans Mono are on Google Fonts and loaded from there.
Keep every size, weight, line height and tracking exactly as listed whichever font renders.
```css
:root {
  --color-background: #000000; /* Background */
  --color-surface: #191A1D; /* Surface */
  --color-text: #FFFFFF; /* Text */
  --color-text-muted: #888888; /* Text muted */
  --color-action: #FFFFFF; /* Action */
  --color-on-action: #000000; /* On action */
  --color-warning: #CE9178; /* Warning */
  --font-body: "Spline Sans", sans-serif; /* Spline Sans */
  --font-code: "Spline Sans Mono", monospace; /* Spline Sans Mono */
  --type-display-large: 40px; /* Display Large, weight 500 */
  --type-display-large-leading: 54px;
  --type-display-medium: 38.4px; /* Display Medium, weight 500 */
  --type-display-medium-leading: 48px;
  --type-display-small: 36px; /* Display Small, weight 500 */
  --type-display-small-leading: 44px;
  --type-headline: 24px; /* Headline, weight 400 */
  --type-headline-leading: 36px;
  --type-title-large: 20px; /* Title Large, weight 500 */
  --type-title-large-leading: 30px;
  --type-title-small: 18px; /* Title Small, weight 400 */
  --type-title-small-leading: 28px;
  --type-body-large: 16px; /* Body Large, weight 400 */
  --type-body-large-leading: 24px;
  --type-body-small: 14px; /* Body Small, weight 400 */
  --type-body-small-leading: 20px;
  --type-label: 12px; /* Label, weight 400 */
  --type-label-leading: 16px;
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-7: 28px;
  --space-8: 32px;
  --space-10: 40px;
  --space-12: 48px;
  --space-14: 56px;
  --space-16: 64px;
  --space-20: 80px;
  --space-22: 88px;
  --space-25: 100px;
  --space-31: 124px;
  --space-32: 128px;
  --space-35: 140px;
  --space-45: 180px;
  --space-50: 200px;
  --radius-md: 6px;
  --radius-lg: 8px;
  --radius-xl: 12px;
  --radius-2xl: 16px;
  --radius-3xl: 24px;
  --elevation-1: rgba(255, 255, 255, 0.06) 0px 0px 0px 1px inset;
  --duration-1: 0.15s;
  --duration-2: 0.2s;
  --ease-1: ease-in-out;
}
```
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: #000000;
  --color-surface: #191A1D;
  --color-text: #FFFFFF;
  --color-text-muted: #888888;
  --color-action: #FFFFFF;
  --color-on-action: #000000;
  --color-warning: #CE9178;
  --font-body: "Spline Sans", sans-serif;
  --font-code: "Spline Sans Mono", monospace;
  --text-display-large: 40px;
  --text-display-large--line-height: 54px;
  --text-display-medium: 38.4px;
  --text-display-medium--line-height: 48px;
  --text-display-small: 36px;
  --text-display-small--line-height: 44px;
  --text-headline: 24px;
  --text-headline--line-height: 36px;
  --text-title-large: 20px;
  --text-title-large--line-height: 30px;
  --text-title-small: 18px;
  --text-title-small--line-height: 28px;
  --text-body-large: 16px;
  --text-body-large--line-height: 24px;
  --text-body-small: 14px;
  --text-body-small--line-height: 20px;
  --text-label: 12px;
  --text-label--line-height: 16px;
  --radius-md: 6px;
  --radius-lg: 8px;
  --radius-xl: 12px;
  --radius-2xl: 16px;
  --radius-3xl: 24px;
  --shadow-e1: rgba(255, 255, 255, 0.06) 0px 0px 0px 1px inset;
  --ease-1: ease-in-out;
}
```
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)", "action": "var(--color-action)", "on-action": "var(--color-on-action)", "warning": "var(--color-warning)" },
  fontFamily: { "body": ["var(--font-body)"], "code": ["var(--font-code)"] },
  borderRadius: { "md": "var(--radius-md)", "lg": "var(--radius-lg)", "xl": "var(--radius-xl)", "2xl": "var(--radius-2xl)", "3xl": "var(--radius-3xl)" },
  boxShadow: { "e1": "var(--elevation-1)" },
}
```

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-body); margin: 0; }
a { color: inherit; }
:focus-visible { outline: 2px solid var(--color-action); outline-offset: 2px; }
```

3. COMPONENTS — MATCH THESE EXACTLY
```css
.card { /* Default */
  background: var(--color-surface);
  border-radius: var(--radius-2xl);
  min-height: 150px;
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--type-body-large);
  font-weight: 400;
  line-height: 18.4px;
}
.card-2 { /* Alternative 1 */
  background: #3A3A3A;
  border-radius: var(--radius-2xl);
  padding: 10px 10px 10px 10px;
  min-height: 100px;
  box-shadow: var(--elevation-1);
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--type-body-large);
  font-weight: 400;
  line-height: 18.4px;
}
.link-3 { /* Inline 3 */
  background: transparent;
  padding: 10px 10px 10px 10px;
  min-height: 38px;
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--type-body-large);
  font-weight: 400;
  line-height: 18.4px;
  /* recorded states: hover */
}
.button { /* Primary */
  background: var(--color-action);
  border-radius: var(--radius-xl);
  padding: 12px 24px 12px 24px;
  min-height: 44px;
  color: var(--color-on-action);
  font-family: var(--font-body);
  font-size: var(--type-body-small);
  font-weight: 500;
  line-height: 20px;
  /* recorded states: hover */
}
.button-2 { /* Secondary */
  background: #0062FF;
  border-radius: var(--radius-xl);
  padding: 16px 24px 16px 24px;
  min-height: 52px;
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--type-body-large);
  font-weight: 400;
  line-height: 20px;
  /* recorded states: hover */
}
.button-3 { /* Tertiary */
  background: transparent;
  padding: 10px 5px 10px 10px;
  min-height: 38px;
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--type-body-large);
  font-weight: 400;
  line-height: 18.4px;
  /* recorded states: collapsed, hover */
}
.nav { /* Default */
  background: transparent;
  min-height: 56px;
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: var(--type-body-large);
  font-weight: 400;
  line-height: 18.4px;
}
.input { /* Default */
  background: transparent;
  padding: 2px 8px 0px 8px;
  min-height: 40px;
  color: var(--color-text);
  font-family: var(--font-body);
  font-size: 15px;
  font-weight: 400;
  line-height: 24px;
}
```
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
- Dark interface on #000000. Keep that ground; do not add a light mode or alternate section backgrounds the system does not have.
- The opening screen carries a large image or video on the left. Leave a [content: hero image or video] slot there, at least half the screen wide; the opening is not text alone.
- #FFFFFF is the action colour. Fill the primary action with it and little else — at most one #FFFFFF-filled element per screen; other accents keep to the uses listed above.
- Type: Spline Sans for body; Spline Sans Mono for code. Hierarchy comes from size and weight, not colour or decoration.
- Everything sits on a 4px grid.
- Corner radii are 6px, 8px, 12px, 16px, 24px — nothing else.
- Body text uses Spline Sans at around 16px, weights 400, 500.
- Headings use the same family as body text; the largest heading is 40px.
- Primary buttons are #FFFFFF, 6px radius, weight 400.
- Cards use 16px corners with a soft shadow.
- Corner radii in use: 16px, 8px, 12px, 24px, 56px.

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 — 620px tall, a strip of 14 small items (logos, links or icons), centred 36px heading (weight 500), image on the left.
2. Statement — 628px tall, a strip of 15 small items (logos, links or icons), centred 18px heading (weight 400).
3. Statement — 1155px tall, centred 36px heading (weight 500), image on the left.
4. Statement — 424px tall, centred 24px heading (weight 400).
5. Split — 2107px tall, split 7 / 5, 24px gap, centred 36px heading (weight 500), full-width image.
6. Statement — 548px tall, centred 24px heading (weight 400) set mid-band.
7. Split — 2107px tall, split 7 / 5, 24px gap, centred 36px heading (weight 500), full-width image.
8. Split — 1094px tall, 2 equal columns, 32px gap, centred 36px heading (weight 500), image on the left.
9. Cards — 722px tall, 3 equal columns, 24px gap, centred 36px heading (weight 500).
10. Cards — 983px tall, 4 equal columns, 24px gap, centred 36px heading (weight 500), image behind the content.
11. Statement — 340px tall, centred 40px heading (weight 500).
12. Footer — 546px tall, 4 equal columns, 65px gap, centred 16px heading (weight 400) set low in the band.
- Content runs 1078px wide with 181px side margins at 1440px; there is no narrower centred container.
- A 56px header stays fixed at the top, transparent over the first section.
- The hero is 620px (0.7 screens): a strip of 14 small items (logos, links or icons), centred 36px heading (weight 500), image on the left.
- Column splits on a 12-column grid: 7/5 (2×), quarters (2×), halves, thirds; gaps of 24px.
- Headings are centred (12 of 12 sections).
- Sections share one background; they are separated by space and lines, not colour bands.
- A typical section is about 983px tall.

COPY SHAPE (MATCH THE LENGTH AND CASE; WRITE YOUR OWN WORDS)
- The main heading is 3 words long.
- Section headings are medium length: typically 7 words.
- Headings are in Title Case.
- The page describes itself in about 25 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) var(--ease-1), background-color var(--duration-1) var(--ease-1), border-color var(--duration-1) var(--ease-1), opacity var(--duration-1) var(--ease-1); }
@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 666px 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 (21:1), Text muted on Background (5.9:1), Action on Background (21:1), Text on Surface (17.4:1), Text muted on Surface (4.9:1), Action on Surface (17.4:1) and On action on Action (21:1).
- 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 one shadow in the tokens, on the components that use them. (1 shadow value was 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: #000000, #FFFFFF, #191A1D, #3A3A3A, #1E1E23, #0062FF, #888888, #CE9178. 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.)
- #0062FF only as small fills (buttons, badges) — never a section background or a large panel. (It covers 0.1% of the page.)
- #CE9178 only for text — never as a section background or a large panel. (It covers under 0.1% of the page.)
- Only the fonts in the tokens: Spline Sans for body; Spline Sans 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 Spline Sans and ui-monospace and Spline Sans Mono; the tokens carry what stands in for them.)
- Headings and large text never heavier than weight 500. Do not make headlines bold to add emphasis. (Every size from 24px up is set at weight 500 or lighter.)
- No all-caps eyebrow labels above headings. (No uppercase text was measured.)
- 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, statement, split, cards, 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 spline.design'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.
- #0062FF covers about 0.1% of the page or less, as on the original.
- #CE9178 covers about 0.1% of the page or less, as on the original.
- No text 24px or larger has a font-weight above 500.
- Every section, including ones the original does not have, uses only this system's colours, type, shapes and spacing.
- 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.