Foundations

• 1: Colour
• 2: Typography
• 3: Space, shape, and motion

1 - Colour

The palette is three scales — midnight, orange, and slate — each expressed as a 12-step ramp in a light and a dark variant. The step numbering follows the Radix convention, which assigns every step a role. Using a step outside its role is the single most common way to break the system.

Core colours

These are the named aliases most projects reach for first. They are shortcuts into the scales, not a separate palette.

• Primary

  #1d3352

  Text, headings, primary surfaces
• Primary Light

  #2b4d78

  Hover states, dark-mode primary
• Primary Dark

  #132440

  Dark backgrounds, navbar, code blocks
• Accent

  #E05232

  CTAs, highlights, active states
• Accent Light

  #ea7558

  Accent hover on dark, syntax strings
• Accent Dark

  #b84228

  Accent pressed state
• Accent Solid

  #cc4528

  Fill for solid controls with white text (4.72:1)
• Secondary

  #546a82

  Supporting text, borders

Step roles

Every scale uses the same twelve roles in the same order:

Midnight

Midnight is the primary. It carries structure, text, and the calm end of the system. Step 9 (#1d3352) is the brand primary and is identical in both modes.

Orange

Orange is the accent. It marks the primary action, the active state, and little else. Step 9 (#E05232) is constant across modes.

Slate

Slate is the secondary — supporting text, borders, and neutral surfaces. Step 9 (#546a82) is the brand secondary and is constant across modes.

Terminal

The three scales cover every surface that has a light mode. A terminal does not: it has one surface, it is dark, and every colour in it is measured against that one background. It also needs six hues where the interface needs three, because programs have been writing to sixteen ANSI slots since long before this system existed.

So the terminal palette is a fourth member of the system rather than a fifth scale — a fixed sixteen-slot palette plus its chrome, derived from the ramps and measured against midnight-dark-1.

Read the provenance column carefully. The bright ramp is the brand: where a hue already exists in the system, the bright slot takes that step verbatim. The normal ramp has no brand equivalent — the scales define one value per semantic role, not a dim and a bright — so each normal slot is its bright counterpart darkened until it reads a step back while still clearing the floor.

Magenta and cyan exist in neither half of the brand. They are here because a terminal requires them, and nowhere else.

Terminal chrome

The accent gets no ANSI slot, because it is not semantic — it marks where you are. That, and the surfaces around the sixteen, live here.

Every non-background value clears 4.5:1 against the surface; the measured floor is 4.95:1. ANSI 0 bright is the one deliberate exception — programs use it for box drawing and rules, not for text.

Configuration for tmux, WezTerm, Kitty, iTerm2, and Zellij is on the Terminal theming page.

Contrast rules

• Never use pure #000 or #fff as text. Use step 12 of the relevant scale: #142438 on light, #c5daf0 on dark.
• Step 9 is constant across modes. The solid accent does not shift when the theme changes.
• Body text targets 4.5:1, large text (≥24px, or ≥18.66px bold) targets 3:1.
• Verify against the actual surface. A step that passes on the app background may fail on an elevated panel.

Where an identity colour cannot carry text

Being the brand colour does not make a value a legible background. White on orange-9 (#E05232) measures 3.87:1 — fine as a mark or a border, but below the floor for button labels. Rather than dilute the accent, the system adds a separate fill for that job:

The same principle produced the code-comment token: when no existing step can do the job accessibly, name a new one rather than misuse a step.

Semantic colours are mode-specific

The callout hues are tuned for dark text on tinted light backgrounds. Used as foregrounds on the dark app surface they fall below AA, so dark mode has its own set:

Dark mode

Both modes are equally supported. See Dark mode for the implementation rules — theme switching, persistence, image treatment, and the always-dark code surface.

2 - Typography

The system uses three typefaces, each with one job. All three are licensed under the SIL Open Font License 1.1 and served from Google Fonts, so there are no bundled font binaries to license or redistribute.

The three families

Loading them:

<link rel="preconnect" href="https://fonts.googleapis.com">
<link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
<link rel="stylesheet" href="https://fonts.googleapis.com/css2?family=Plus+Jakarta+Sans:wght@400;500;600;700;800&family=Source+Sans+3:wght@400;500;600&family=IBM+Plex+Mono:wght@400;500&display=swap">

The ramp

Every row below is set in the family, size, weight, and line-height it documents — this is the live specimen, not a picture of one.

Rules

• Letter-spacing tightens to −0.3px above 20px. Large type set at default tracking reads loose and unresolved.
• Overline is a label, not a heading. 11px, 600, uppercase, 0.08em tracking. Use it above a heading, never as one.
• Body copy is 16px / 1.65. This is the reading size for documentation and long-form prose. Do not set body text below 14px.
• Never set body copy in Plus Jakarta Sans, and never set headings in Source Sans 3. The split is what makes the voice recognisable.

3 - Space, shape, and motion

Spacing

A 4px base with a nine-step scale. Every margin, padding, and gap resolves to one of these values.

Content sits inside a 1100px measure. Wider viewports gain margin, not line length.

Radius

Radius is a signal of scale: the larger the surface, the larger the radius. Mixing radii on nested surfaces reads as a mistake — a 6px control inside a 9px card is correct; a 13px control inside a 6px card is not.

Elevation

Four levels. Shadows are soft and low-contrast; the system leans on borders and surface tint before it reaches for shadow.

In dark mode, elevation is expressed by lightening the surface rather than deepening the shadow — a shadow on a near-black background is invisible.

Motion

Things slide into place. They do not bounce.

Durations

Easing

Motion rules

• All animation wraps in @media (prefers-reduced-motion: no-preference), or is disabled under prefers-reduced-motion: reduce.
• CSS-only for HTML. For React, use Framer Motion with these same timing values.
• Never animate text character-by-character.
• Page transitions cap at 400ms.

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}