Swiss Design System

A design system rooted in the Swiss International Style of the 1950s–60s: grotesque typography, rigorous grid, bold geometric forms, generous whitespace, and restrained color.

Six Principles

1. Grid first. Every layout lives on a 12-column grid with an 8px base unit.
2. Mobile first, always. Design for the smallest viewport first, then expand. Every layout must work at 320px and at 1440px. Use sm:, md:, lg: Tailwind prefixes systematically.
3. Whitespace is structure. Generous padding and margins are not waste — they are the design.
4. Opacity, not hue, creates hierarchy. Never introduce a second color to indicate text weight or importance. Use opacity.
5. One accent. Each project gets exactly one accent color, used sparingly at multiple opacities.
6. Narrow columns. Body text never exceeds max-w-[60ch]. Wider columns hurt legibility.

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Typography

Primary font: IBM Plex Sans (Google Fonts)

<link rel="preconnect" href="https://fonts.googleapis.com">
<link href="https://fonts.googleapis.com/css2?family=IBM+Plex+Sans:ital,wght@0,300;0,400;0,500;0,600;1,300;1,400&display=swap" rel="stylesheet">

Fallback chain (in order of preference):

Font	Source	Character
IBM Plex Sans	Google Fonts	Primary. Rational, slightly condensed, 1960s systems rationalism
Hanken Grotesk	Google Fonts	Closest to Neue Haas Grotesk lineage
Barlow	Google Fonts	Condensed Swiss-grid proportions, strong vertical rhythm
Host Grotesk	Google Fonts	Warm grotesque, good at all sizes
DM Sans	Google Fonts	Clean neo-grotesque fallback
system-ui	Built-in	Last resort

font-family: 'IBM Plex Sans', 'Hanken Grotesk', 'Barlow', 'Host Grotesk', 'DM Sans', system-ui, sans-serif;

Type scale:

Role	Tailwind	Line height	Max width
Display	text-7xl font-light tracking-tight	leading-none	unconstrained
H1	text-5xl font-light tracking-tight	leading-tight	unconstrained
H2	text-3xl font-light tracking-tight	leading-snug	unconstrained
H3	text-xl font-normal	leading-snug	unconstrained
Body	text-base font-normal	leading-relaxed	max-w-[60ch]
Small	text-sm font-normal	leading-relaxed	max-w-[60ch]
Caption	text-xs font-normal tracking-wide uppercase	leading-normal	unconstrained
Mono	font-mono text-sm	leading-relaxed	max-w-[60ch]

• Headings: font-light (300) or font-normal (400). Never bold for headings.
• Emphasis within body: font-medium (500). Never font-bold (700).
• Letter spacing on display/h1: tracking-tight (-0.02em).
• Captions and labels: tracking-wide uppercase text-xs.

Typographic details

The Swiss style depends on typographic precision. These rules are non-negotiable:

• Use the ellipsis character …, never three periods ....
• Use curly quotes " " and ' ', never straight quotes " '.
• Loading and progress states end with an ellipsis: Loading…, Saving….
• Number columns and tables use font-variant-numeric: tabular-nums (Tailwind: tabular-nums) so digits align vertically.
• Headings use text-wrap: balance (Tailwind: text-balance) to prevent widows. Body paragraphs use text-pretty where supported.
• Non-breaking spaces between value and unit, and inside brand names: 10 MB, ⌘ K.

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Color System

Stone palette (light mode → dark mode)

Role	Light	Dark	Tailwind
Page background	stone-50	stone-950	bg-stone-50 dark:bg-stone-950
Surface / card	stone-100	stone-900	bg-stone-100 dark:bg-stone-900
Subtle surface	stone-200	stone-800	bg-stone-200 dark:bg-stone-800
Border	stone-200	stone-800	border-stone-200 dark:border-stone-800
Subtle border	stone-100	stone-900	border-stone-100 dark:border-stone-900
Primary text	stone-900	stone-50	text-stone-900 dark:text-stone-50
Secondary text	stone-900/70	stone-50/70	text-stone-900/70 dark:text-stone-50/70
Tertiary text	stone-900/40	stone-50/40	text-stone-900/40 dark:text-stone-50/40
Placeholder	stone-900/30	stone-50/30	text-stone-900/30 dark:text-stone-50/30

Opacity hierarchy (the core rule)

To make text less dominant, reduce opacity — never change the hue.

Full presence:   text-stone-900          (primary)
Softer:          text-stone-900/70       (secondary, labels)
Quiet:           text-stone-900/40       (tertiary, captions)
Ghosted:         text-stone-900/20       (disabled, placeholder)

Dark mode: replace stone-900 with stone-50. The opacity values stay identical.

Accent color

Each project uses one accent color. Default is Swiss poster red.

Name	Hex	Tailwind arbitrary
Swiss Red (default)	#C8102E	[#C8102E]
Cobalt	#003B8E	[#003B8E]
Golden	#F0B429	[#F0B429]
Forest	#2D6A4F	[#2D6A4F]

Use accent at these opacities only:

Full:    bg-[#C8102E]          text-[#C8102E]
Muted:   bg-[#C8102E]/60       text-[#C8102E]/60
Subtle:  bg-[#C8102E]/20       (backgrounds, tints)
Ghost:   bg-[#C8102E]/10       (very light tints)

---

Spacing & Grid

Base unit: 8px. All spacing is a multiple of 8.

Token	Value	Usage
gap-2	8px	Tight inline gaps
gap-4	16px	Component internal
gap-8	32px	Between components
gap-16	64px	Between sections
py-16	64px	Section padding (minimum)
py-24	96px	Section padding (standard)
py-32	128px	Section padding (generous)

Grid:

<!-- 12-column grid — always mobile-first, columns collapse to full-width on small screens -->
<div class="grid grid-cols-12 gap-4 md:gap-8">
  <div class="col-span-12 md:col-span-8">...</div>
  <div class="col-span-12 md:col-span-4">...</div>
</div>

Max content width: max-w-5xl or max-w-6xl with mx-auto px-4 md:px-8.

---

Responsive Design

The Swiss grid adapts fluidly across viewports. Every layout decision must be made at two scales: mobile (single column, generous vertical rhythm) and desktop (multi-column, horizontal tension).

Breakpoint strategy:

Prefix	Width	Use for
(none)	0px+	Mobile — single column, full width
sm:	640px+	Large phones, small tablets
md:	768px+	Tablets, narrow desktop — introduce 2-col layouts
lg:	1024px+	Desktop — full 12-col grid, max content width

Mobile layout rules:

• All grid columns collapse to col-span-12
• Section padding reduces: py-16 md:py-24 lg:py-32
• Horizontal padding tightens: px-4 md:px-8
• Display type scales down: text-5xl md:text-7xl lg:text-8xl
• Multi-column nav collapses to hamburger or hidden
• Tables scroll horizontally: wrap in overflow-x-auto
• Side-by-side cards stack vertically: grid-cols-1 md:grid-cols-2 lg:grid-cols-3

Fluid type pattern:

<!-- Scale display type fluidly across viewports -->
<h1 class="text-4xl sm:text-5xl md:text-6xl lg:text-7xl font-normal tracking-tight leading-none">
  Swiss International Style
</h1>

<!-- Or use clamp() for truly fluid scaling -->
<h1 class="text-[clamp(2rem,6vw,5rem)] font-normal tracking-tight leading-none">
  Swiss International Style
</h1>

Responsive section pattern:

<section class="py-16 md:py-24 lg:py-32 border-b border-stone-200 dark:border-stone-800">
  <div class="max-w-6xl mx-auto px-4 md:px-8">
    <div class="grid grid-cols-1 md:grid-cols-2 lg:grid-cols-3 gap-8">
      ...
    </div>
  </div>
</section>

Touch targets: All interactive elements must be at least 44×44px on mobile. Use min-h-[44px] min-w-[44px] for buttons and nav links.

Navigation on mobile: Collapse to a minimal top bar. Hide secondary nav links below md:. Never use hamburger menus with deeply nested hierarchies — the Swiss style favors flat, clear navigation.

---

Dark Mode

Use Tailwind's media strategy (respects system preference automatically):

// tailwind.config.js
darkMode: 'media'

Every color token has a dark: variant. See the stone palette table above. Never use bg-black or bg-white — always use stone scale.

color-scheme

Tailwind only restyles your code. The browser still renders scrollbars, native form controls, and the canvas before CSS loads using its own defaults. Without color-scheme, a Swiss page in dark mode shows light scrollbars and light-mode native inputs against bg-stone-950.

Always declare both schemes on <html>:

html { color-scheme: light dark; }

Or via meta tag (parsed before CSS, prevents flash):

<meta name="color-scheme" content="light dark">

Also set <meta name="theme-color"> to match the page background so the mobile browser chrome blends in.

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Gotchas

• Never use a second color to signal hierarchy. Opacity only. text-stone-900/70, not text-stone-500.
• Never exceed max-w-[60ch] for body text. Wider columns are illegible.
• Never bg-white or bg-black. Use bg-stone-50 / bg-stone-950.
• IBM Plex Sans is not a system font. Always include the Google Fonts <link> tag.
• One accent per project. Do not introduce a second accent color. Use opacity variations instead.
• Headings are light, not bold. font-light for display and h1, font-normal for h2–h3.
• No border-radius on structural elements. Inputs, cards, and containers use rounded-none or at most rounded-sm. The Swiss style is rectilinear.
• Section padding is generous. Minimum py-16, standard py-24. Never less.
• Every layout must work on mobile. Default (no prefix) classes are mobile. Always add md: and lg: variants for larger viewports. Never build desktop-first and try to retrofit mobile.
• Tables on mobile need overflow-x-auto. Never let a wide table break mobile layout.
• Touch targets minimum 44px. Buttons, links, and nav items must be tappable on mobile.
• Fluid type, not fixed. Use responsive type classes (text-3xl md:text-5xl) or clamp() — never a single fixed size that works only at one viewport.
• Never outline-none without a focus replacement. Interactive elements need a visible focus indicator. Use focus-visible:ring-2 focus-visible:ring-stone-900 dark:focus-visible:ring-stone-50 (or the accent) instead. Prefer :focus-visible over :focus so the ring only appears on keyboard navigation.
• Honor prefers-reduced-motion. If you add transitions or animations, gate them: motion-safe:transition motion-reduce:transition-none. Animate only transform and opacity. Never transition: all.
• Set color-scheme: light dark on <html>. Otherwise scrollbars and native form controls stay light in dark mode.
• Straight quotes and ... are bugs. Use curly quotes and the … character.

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Behavior, accessibility, and quality

This skill is an aesthetic and visual system. It does not cover accessibility, focus management, form behavior, hydration, performance, or interaction quality.

For those, defer to the Vercel Web Interface Guidelines, which are framework-agnostic and complementary:

• Skill: vercel-labs/agent-skills/web-design-guidelines
• Raw rules: https://raw.githubusercontent.com/vercel-labs/web-interface-guidelines/main/command.md

After applying Swiss styling, fetch the rules above and audit the result for accessibility, focus states, form behavior, animation safety, performance, and i18n. Treat findings as required fixes, not suggestions. Where the two systems overlap (typography niceties, dark mode, focus rings), the rules already inlined in this SKILL.md take precedence.

When to read reference files

Task	File
Full color token table, CSS custom properties, dark mode details	references/design-system.md
Tailwind component patterns: buttons, cards, nav, forms, badges	references/components.md
Paste-ready tailwind.config.js and CSS @theme block	references/tailwind-config.md
Applying this system to an existing page, audit checklist	references/prompting.md