Shadcn Theming

shadcn Theming Skill

Patterns for customizing shadcn/ui themes in NextSpark using CSS variables and the tweakcn.com editor.

Fundamental Principle

THE THEME IS THE SINGLE SOURCE OF TRUTH FOR DESIGN TOKENS.

All visual customization happens in the theme's globals.css. No inline colors, no hardcoded values.

themes/{THEME}/styles/globals.css → BUILD → core/theme-styles.css → App

When to Use This Skill

• Initializing a new project's design system
• Customizing colors for a client project
• Converting design system from mock to theme
• Understanding the theme build process

Architecture Overview

THEME CSS STRUCTURE:

themes/{THEME}/styles/
├── globals.css      # CSS variables (THE DESIGN SYSTEM)
│   ├── :root        # Light mode tokens
│   ├── .dark        # Dark mode tokens
│   └── @theme inline # Tailwind v4 mappings
│
└── components.css   # Component-specific styles (optional)

BUILD OUTPUT:
└── core/theme-styles.css  # Auto-generated (DO NOT EDIT)

Using tweakcn.com

Step 1: Access the Editor

Navigate to: https://tweakcn.com/editor/theme

The editor provides:

• Visual color picker with OKLCH support
• Light/Dark mode preview
• Real-time component preview
• Export in CSS format

Step 2: Customize Your Theme

1. Base Colors:

   • Background/Foreground
   • Primary/Secondary
   • Accent/Muted
   • Destructive

2. Component Colors:

   • Card surfaces
   • Popover/Dropdown
   • Sidebar (if using dashboard)

3. Design Tokens:

   • Border radius
   • Shadows
   • Typography (font families)

Step 3: Export CSS

Click "Copy CSS" or "Export" to get:

:root {
  --background: oklch(1 0 0);
  --foreground: oklch(0.145 0 0);
  --primary: oklch(0.55 0.2 250);
  --primary-foreground: oklch(0.985 0 0);
  /* ... all variables */
}

.dark {
  --background: oklch(0.145 0 0);
  --foreground: oklch(0.985 0 0);
  /* ... dark mode overrides */
}

CSS Variable Reference

Required Variables (All Must Be Defined)

:root {
  /* === SURFACE COLORS === */
  --background: oklch(L C H);      /* Page background */
  --foreground: oklch(L C H);      /* Primary text */
  --card: oklch(L C H);            /* Card surfaces */
  --card-foreground: oklch(L C H); /* Card text */
  --popover: oklch(L C H);         /* Dropdown/popover bg */
  --popover-foreground: oklch(L C H);

  /* === INTERACTIVE COLORS === */
  --primary: oklch(L C H);           /* Primary buttons, links */
  --primary-foreground: oklch(L C H); /* Text on primary */
  --secondary: oklch(L C H);         /* Secondary buttons */
  --secondary-foreground: oklch(L C H);
  --accent: oklch(L C H);            /* Hover highlights */
  --accent-foreground: oklch(L C H);

  /* === STATE COLORS === */
  --muted: oklch(L C H);             /* Muted backgrounds */
  --muted-foreground: oklch(L C H);  /* Placeholder text */
  --destructive: oklch(L C H);       /* Error/danger */
  --destructive-foreground: oklch(L C H);

  /* === BORDER & INPUT === */
  --border: oklch(L C H);            /* Border color */
  --input: oklch(L C H);             /* Input border */
  --ring: oklch(L C H);              /* Focus ring */

  /* === CHART COLORS === */
  --chart-1: oklch(L C H);
  --chart-2: oklch(L C H);
  --chart-3: oklch(L C H);
  --chart-4: oklch(L C H);
  --chart-5: oklch(L C H);

  /* === SIDEBAR (if dashboard) === */
  --sidebar: oklch(L C H);
  --sidebar-foreground: oklch(L C H);
  --sidebar-primary: oklch(L C H);
  --sidebar-primary-foreground: oklch(L C H);
  --sidebar-accent: oklch(L C H);
  --sidebar-accent-foreground: oklch(L C H);
  --sidebar-border: oklch(L C H);
  --sidebar-ring: oklch(L C H);

  /* === TYPOGRAPHY === */
  --font-sans: ui-sans-serif, system-ui, ...;
  --font-serif: ui-serif, Georgia, ...;
  --font-mono: ui-monospace, SFMono-Regular, ...;

  /* === DESIGN TOKENS === */
  --radius: 0.625rem;              /* Base border radius */
  --spacing: 0.25rem;              /* Base spacing unit */

  /* === SHADOWS === */
  --shadow-2xs: ...;
  --shadow-xs: ...;
  --shadow-sm: ...;
  --shadow: ...;
  --shadow-md: ...;
  --shadow-lg: ...;
  --shadow-xl: ...;
  --shadow-2xl: ...;
}

Dark Mode Override

.dark {
  /* Only override colors that change in dark mode */
  /* Typically invert backgrounds/foregrounds */

  --background: oklch(0.145 0 0);       /* Dark bg */
  --foreground: oklch(0.985 0 0);       /* Light text */

  --card: oklch(0.205 0 0);             /* Slightly lighter */
  --card-foreground: oklch(0.985 0 0);

  --primary: oklch(0.922 0 0);          /* Often lighter in dark mode */
  --primary-foreground: oklch(0.205 0 0);

  --muted: oklch(0.269 0 0);
  --muted-foreground: oklch(0.708 0 0);

  --border: oklch(0.275 0 0);
  --input: oklch(0.325 0 0);

  /* Destructive typically stays similar hue but adjusted */
  --destructive: oklch(0.704 0.191 22);

  /* Chart colors usually stay the same */
}

Tailwind v4 Theme Mapping

REQUIRED: Map CSS variables to Tailwind for class-based styling.

@theme inline {
  /* Colors */
  --color-background: var(--background);
  --color-foreground: var(--foreground);
  --color-card: var(--card);
  --color-card-foreground: var(--card-foreground);
  --color-popover: var(--popover);
  --color-popover-foreground: var(--popover-foreground);
  --color-primary: var(--primary);
  --color-primary-foreground: var(--primary-foreground);
  --color-secondary: var(--secondary);
  --color-secondary-foreground: var(--secondary-foreground);
  --color-muted: var(--muted);
  --color-muted-foreground: var(--muted-foreground);
  --color-accent: var(--accent);
  --color-accent-foreground: var(--accent-foreground);
  --color-destructive: var(--destructive);
  --color-destructive-foreground: var(--destructive-foreground);
  --color-border: var(--border);
  --color-input: var(--input);
  --color-ring: var(--ring);
  --color-chart-1: var(--chart-1);
  --color-chart-2: var(--chart-2);
  --color-chart-3: var(--chart-3);
  --color-chart-4: var(--chart-4);
  --color-chart-5: var(--chart-5);
  --color-sidebar: var(--sidebar);
  --color-sidebar-foreground: var(--sidebar-foreground);
  --color-sidebar-primary: var(--sidebar-primary);
  --color-sidebar-primary-foreground: var(--sidebar-primary-foreground);
  --color-sidebar-accent: var(--sidebar-accent);
  --color-sidebar-accent-foreground: var(--sidebar-accent-foreground);
  --color-sidebar-border: var(--sidebar-border);
  --color-sidebar-ring: var(--sidebar-ring);

  /* Typography */
  --font-sans: var(--font-sans);
  --font-mono: var(--font-mono);
  --font-serif: var(--font-serif);

  /* Radius */
  --radius-sm: calc(var(--radius) - 4px);
  --radius-md: calc(var(--radius) - 2px);
  --radius-lg: var(--radius);
  --radius-xl: calc(var(--radius) + 4px);

  /* Shadows */
  --shadow-2xs: var(--shadow-2xs);
  --shadow-xs: var(--shadow-xs);
  --shadow-sm: var(--shadow-sm);
  --shadow: var(--shadow);
  --shadow-md: var(--shadow-md);
  --shadow-lg: var(--shadow-lg);
  --shadow-xl: var(--shadow-xl);
  --shadow-2xl: var(--shadow-2xl);
}

Color Space: OKLCH

shadcn/ui uses OKLCH color space for perceptually uniform colors.

OKLCH Format

oklch(Lightness Chroma Hue)

- Lightness: 0-1 (0 = black, 1 = white)
- Chroma: 0-0.4 (0 = gray, higher = more saturated)
- Hue: 0-360 (color angle on color wheel)

Common Colors in OKLCH

Converting HEX to OKLCH

Use online converters or JavaScript:

// Using culori library
import { oklch, formatCss } from 'culori'

const hex = '#137fec'
const oklchColor = oklch(hex)
// { mode: 'oklch', l: 0.55, c: 0.2, h: 250 }

const cssValue = `oklch(${oklchColor.l.toFixed(4)} ${oklchColor.c.toFixed(4)} ${oklchColor.h?.toFixed(4) || 0})`
// "oklch(0.5500 0.2000 250.0000)"

DS Initialization Workflow

Path 1: From tweakcn.com (Recommended)

# 1. Customize at tweakcn.com/editor/theme
# 2. Copy the CSS export
# 3. Run the command with the CSS file

/theme:design-system path/to/exported-theme.css

The command will:

1. Parse the CSS file
2. Validate required variables
3. Add missing @theme inline mappings if needed
4. Write to active theme's globals.css
5. Run pnpm theme:build

Path 2: From Mock Analysis

Use how-to:customize-theme command with a mock folder:

# Extract DS from a mock design
how-to:customize-theme --from-mock path/to/mock/folder

The process will:

1. Read the design-system skill for patterns
2. Extract color palette from mock's Tailwind config
3. Convert HEX to OKLCH format
4. Generate dark mode by inverting lightness
5. Write to active theme's globals.css
6. Run pnpm theme:build

Theme Build Process

After modifying globals.css:

# Rebuild theme CSS
pnpm theme:build

# Or with watch mode
pnpm theme:build --watch

What Build Does:

1. Reads NEXT_PUBLIC_ACTIVE_THEME from .env
2. Finds theme at themes/{THEME}/styles/
3. Concatenates globals.css + components.css
4. Writes to core/theme-styles.css
5. Copies assets to public/theme/

Validation Checklist

Before finalizing theme customization:

• All required CSS variables defined in :root
• All dark mode overrides in .dark
• @theme inline section present with all mappings
• Colors use OKLCH format (not HEX or HSL)
• Font stacks include fallbacks
• --radius uses rem units
• pnpm theme:build runs without errors
• Light mode looks correct
• Dark mode looks correct
• Components render properly

Common Patterns

Brand Color Integration

:root {
  /* Brand blue as primary */
  --primary: oklch(0.55 0.2 250);          /* #137fec equivalent */
  --primary-foreground: oklch(0.985 0 0);  /* White text on blue */

  /* Brand blue tint for secondary */
  --secondary: oklch(0.95 0.03 250);       /* Very light blue */
  --secondary-foreground: oklch(0.25 0 0); /* Dark text */

  /* Brand blue for accent */
  --accent: oklch(0.92 0.05 250);          /* Light blue hover */
  --accent-foreground: oklch(0.25 0 0);
}

Dark Theme with Color Preservation

.dark {
  /* Keep brand color vibrant in dark mode */
  --primary: oklch(0.65 0.2 250);          /* Slightly lighter */
  --primary-foreground: oklch(0.1 0 0);    /* Dark text on light primary */

  /* Muted versions for backgrounds */
  --secondary: oklch(0.25 0.03 250);       /* Dark blue-gray */
  --secondary-foreground: oklch(0.95 0 0); /* Light text */
}

Anti-Patterns

/* ❌ NEVER: Use HEX or HSL in globals.css */
--primary: #137fec;
--primary: hsl(210, 100%, 50%);

/* ✅ CORRECT: Use OKLCH */
--primary: oklch(0.55 0.2 250);

/* ❌ NEVER: Skip dark mode */
/* (Will look terrible in dark mode) */

/* ✅ CORRECT: Define complete dark mode */
.dark {
  --background: oklch(0.145 0 0);
  /* ... all overrides */
}

/* ❌ NEVER: Skip @theme inline */
/* (Tailwind classes won't work) */

/* ✅ CORRECT: Include complete mapping */
@theme inline {
  --color-background: var(--background);
  /* ... all mappings */
}

/* ❌ NEVER: Edit core/theme-styles.css */
/* (Will be overwritten on next build) */

/* ✅ CORRECT: Edit themes/{THEME}/styles/globals.css */

Related Skills

• tailwind-theming - Tailwind CSS patterns and buildSectionClasses
• design-system - Token mapping from mocks
• shadcn-components - Component usage patterns