# Substack gradient

Gradients derived from Substack's published colour tokens (nominative use; no brand assets). Deterministic: the same values are served as `--brand-gradient*` in the brand's brand.css.

- Page: https://brandsweets.com/gradients/brands/substack-com
- Brand colors: https://brandsweets.com/colors/brands/substack-com · Brand page: https://brandsweets.com/b/substack-com
- Palette: primary #fc5404, secondary #0083d5, accents #ff6719
- Source: https://substack.com (extracted 2026-09-02)

## Brand gradient

ΔH 152° > 140° — interpolating in oklch (shorter hue) keeps the midpoint saturated.

- CSS: `linear-gradient(135deg in oklch shorter hue, #fc5404 0%, #0083d5 100%)`
- Tailwind: `bg-linear-to-br/oklch from-[#fc5404] to-[#0083d5]`
- Contrast (worst point): white 3.28:1 AA-large · black 5.18:1 AA · banding medium
- Maker: https://brandsweets.com/gradients/new/v1.fc5404-0083d5?a=135&in=oklch&hue=shorter

## Hero background

Chroma ×0.35 so it can carry text; ink white (inkFor at the midpoint). L shifted −0.10 until the ink passes AA at the worst point (4.60:1).

- CSS: `linear-gradient(135deg in oklch shorter hue, #a06755 0%, #466480 100%)`
- Tailwind: `bg-linear-to-br/oklch from-[#a06755] to-[#466480]`
- Contrast (worst point): white 4.60:1 AA · black 3.40:1 AA-large · banding high · ink #ffffff
- Maker: https://brandsweets.com/gradients/new/v1.a06755-466480?a=135&in=oklch&hue=shorter

## Button / CTA

ΔL 0.08 top→bottom in the primary's hue (a lit surface, not a rainbow); hover L +0.03, active L −0.03. L shifted −0.10 so white ink gets as close as the ±0.1 bound allows to AA on the surface and both states (worst 3.69:1). Ink is below AA (3.69:1 at the worst point) — use it for large text only, or pick a darker/lighter primary for buttons.

- CSS: `linear-gradient(180deg in oklch shorter hue, #e63e00 0%, #c42700 100%)`
- Tailwind: `bg-linear-to-b/oklch from-[#e63e00] to-[#c42700]`
- Contrast (worst point): white 4.16:1 AA-large · black 3.64:1 AA-large · banding high · ink #ffffff
- Maker: https://brandsweets.com/gradients/new/v1.e63e00-c42700?a=180&in=oklch&hue=shorter
- Hover: `linear-gradient(180deg in oklch shorter hue, #f14900 0%, #d22d00 100%)`
- Active: `linear-gradient(180deg in oklch shorter hue, #db3200 0%, #b62200 100%)`

## Tonal ramp

- CSS: `linear-gradient(135deg in oklch shorter hue, #ffb599 0%, #fc5404 50%, #b12000 100%)`
- Tailwind: `bg-linear-to-br/oklch from-[#ffb599] via-[#fc5404] to-[#b12000]`
- Contrast (worst point): white 1.70:1 fail · black 3.08:1 AA-large · banding high
- Maker: https://brandsweets.com/gradients/new/v1.ffb599-fc5404-b12000?a=135&in=oklch&hue=shorter

## Analogous

Partner hue from the analogous rule at the source colour's lightness.

- CSS: `linear-gradient(135deg in oklab, #fc5404 0%, #fe4179 100%)`
- Tailwind: `bg-linear-to-br/oklab from-[#fc5404] to-[#fe4179]`
- Contrast (worst point): white 3.27:1 AA-large · black 6.24:1 AA · banding high
- Maker: https://brandsweets.com/gradients/new/v1.fc5404-fe4179?a=135

## Complementary

Partner hue from the complementary rule at the source colour's lightness. ΔH 180° > 140° — interpolating in oklch (shorter hue) keeps the midpoint saturated.

- CSS: `linear-gradient(135deg in oklch shorter hue, #fc5404 0%, #05a6c7 100%)`
- Tailwind: `bg-linear-to-br/oklch from-[#fc5404] to-[#05a6c7]`
- Contrast (worst point): white 2.87:1 fail · black 6.33:1 AA · banding medium
- Maker: https://brandsweets.com/gradients/new/v1.fc5404-05a6c7?a=135&in=oklch&hue=shorter

## Triadic

Partner hue from the triadic rule at the source colour's lightness.

- CSS: `linear-gradient(135deg in oklab, #fc5404 0%, #06b171 100%)`
- Tailwind: `bg-linear-to-br/oklab from-[#fc5404] to-[#06b171]`
- Contrast (worst point): white 2.78:1 fail · black 6.40:1 AA · banding medium
- Maker: https://brandsweets.com/gradients/new/v1.fc5404-06b171?a=135

## CSS custom properties (brand.css)

```css
:root {
  /* Brand gradient (derived) */
  /* worst-case contrast: white 3.28:1 AA-large, black 5.18:1 AA */
  --brand-gradient: linear-gradient(135deg in oklch shorter hue, #fc5404 0%, #0083d5 100%);
  /* hero — worst-case contrast: white 4.60:1 AA, black 3.40:1 AA-large; ink passes AA at the worst point */
  --brand-gradient-hero: linear-gradient(135deg in oklch shorter hue, #a06755 0%, #466480 100%);
  --brand-gradient-hero-ink: #ffffff;
  /* button — worst-case contrast: white 4.16:1 AA-large, black 3.64:1 AA-large */
  --brand-gradient-button: linear-gradient(180deg in oklch shorter hue, #e63e00 0%, #c42700 100%);
  --brand-gradient-button-hover: linear-gradient(180deg in oklch shorter hue, #f14900 0%, #d22d00 100%);
  --brand-gradient-button-active: linear-gradient(180deg in oklch shorter hue, #db3200 0%, #b62200 100%);
  --brand-gradient-button-ink: #ffffff;
  /* button ink: 3.7:1 — below AA */
}
```

## Gradient maker

Every maker URL is the gradient's state: `/gradients/new/v1.<hex>-<hex>[_pos]?a=135&in=oklch&hue=shorter&e=soft&g=8`. Hand one to a human, let them refine, and read the link they return.

## Connect an agent

Point any MCP client at the BrandSweets gradients endpoint for the same engine and corpus:

- Endpoint: https://mcp.brandsweets.com/gradients/mcp
- Tools: `make_gradient` (2–5 colours → CSS with the interpolation space, Tailwind v4, SVG, PNG URL, DTCG token + the contrast/banding/gamut report), `brand_gradients` (brand slug or palette → brand gradient, hero, button, variants).
- Resource: `gradients://corpus` — the whole bundled corpus as JSON.