Style Modus Components with Tailwind

Style Modus components using custom border and opacity utilities that work with CSS variables, avoiding Tailwind patterns that don't work with runtime CSS variables.

When to Use

Use this skill when:

•Styling Modus components with borders
•Applying opacity to design system colors
•Creating theme-aware components
•Avoiding common Tailwind + CSS variable pitfalls
•Ensuring components work in all 6 Modus themes

The Core Problem

Tailwind CSS processes colors at build time, but Modus Design System uses CSS variables that resolve at runtime. This creates incompatibilities:

•❌ border-red-500 - Hardcoded color, not theme-aware
•❌ text-foreground/80 - Doesn't work with CSS variables
•❌ border border-destructive - May not work reliably

Solution: Use custom utilities that work with CSS variables at runtime.

Reference Documentation

For detailed technical explanation, see: docs/tailwind-css-variables-problem.md

Custom Border Utilities

Available Border Utilities

Standard borders (1px):

•border-default - Default border color
•border-success - Success color border
•border-warning - Warning color border
•border-destructive - Error/destructive color border
•border-primary - Primary/info color border

Thick borders (2px):

•border-thick - Thick default border
•border-thick-success - Thick success border
•border-thick-warning - Thick warning border
•border-thick-destructive - Thick destructive border
•border-thick-primary - Thick primary border

Dashed borders:

•border-dashed - Dashed default border
•border-dashed-success - Dashed success border
•border-dashed-warning - Dashed warning border
•border-dashed-destructive - Dashed destructive border

Directional borders:

•border-top-default, border-bottom-success, border-left-warning, border-right-destructive
•Pattern: border-{direction}-{color}

Correct Border Usage

tsx

// ✅ CORRECT: Use custom border utilities
<div className="border-destructive">Error message</div>
<div className="border-success">Success message</div>
<div className="border-thick-primary">Important content</div>
<div className="border-bottom-default">Separator</div>

// ❌ WRONG: Don't use Tailwind color classes
<div className="border border-red-500">Error</div>
<div className="border-2 border-green-500">Success</div>
<div className="border border-blue-500">Info</div>

Border Examples

tsx

// Alert with border
<div className="bg-card border-destructive rounded-lg p-4">
  <div className="text-destructive font-semibold">Error</div>
  <div className="text-foreground">Something went wrong</div>
</div>

// Card with border
<div className="bg-card border-default rounded-lg p-6">
  <div className="text-foreground">Card content</div>
</div>

// Success indicator
<div className="border-thick-success rounded p-4">
  <div className="text-success">Operation successful</div>
</div>

Custom Opacity Utilities

Available Opacity Levels

Opacity levels: 80%, 60%, 40%, 20%

Pattern: {property}-{color}-{opacity}

Text Opacity

tsx

// ✅ CORRECT: Use custom opacity utilities
<div className="text-foreground-80">Subheading (80% opacity)</div>
<div className="text-foreground-60">Description (60% opacity)</div>
<div className="text-muted-foreground-40">Hint (40% opacity)</div>
<div className="text-primary-80">Primary text with opacity</div>

// ❌ WRONG: Don't use Tailwind opacity syntax
<div className="text-foreground/80">Doesn't work</div>
<div className="text-primary/60">Doesn't work</div>

Background Opacity

tsx

// ✅ CORRECT: Background with opacity
<div className="bg-primary-20">Subtle primary background</div>
<div className="bg-destructive-40">Warning background</div>
<div className="bg-success-60">Success background</div>

// ❌ WRONG: Tailwind opacity syntax
<div className="bg-primary/20">Doesn't work</div>
<div className="bg-destructive/40">Doesn't work</div>

Border Opacity

tsx

// ✅ CORRECT: Border with opacity
<div className="border border-destructive-40">Subtle error border</div>
<div className="border border-primary-60">Primary border with opacity</div>

// ❌ WRONG: Tailwind opacity syntax
<div className="border border-destructive/40">Doesn't work</div>

Available Color + Opacity Combinations

Text opacity:

•text-foreground-80, text-foreground-60, text-foreground-40, text-foreground-20
•text-muted-foreground-80, text-muted-foreground-60, etc.
•text-primary-80, text-primary-60, text-primary-40, text-primary-20
•text-secondary-80, text-secondary-60, etc.
•text-destructive-80, text-destructive-60, etc.
•text-warning-80, text-warning-60, etc.
•text-success-80, text-success-60, etc.

Background opacity:

•bg-foreground-80, bg-foreground-60, bg-foreground-40, bg-foreground-20
•bg-primary-80, bg-primary-60, bg-primary-40, bg-primary-20
•Same pattern for: secondary, destructive, warning, success, muted

Border opacity:

•border-destructive-80, border-destructive-60, etc.
•Same pattern for all border colors

Complete Styling Examples

Alert Component

tsx

// ✅ CORRECT: Theme-aware alert
<div className="bg-card border-destructive rounded-lg p-4">
  <div className="flex items-center gap-2">
    <i className="modus-icons text-destructive">warning</i>
    <div className="text-destructive font-semibold">Error</div>
  </div>
  <div className="text-foreground-80 mt-2">Error message details</div>
</div>

// ❌ WRONG: Hardcoded colors
<div className="bg-white border border-red-500 rounded-lg p-4">
  <div className="text-red-500">Error</div>
  <div className="text-gray-600/80">Details</div>
</div>

Card Component

tsx

// ✅ CORRECT: Theme-aware card
<div className="bg-card border-default rounded-lg p-6 shadow-sm">
  <div className="text-foreground text-xl font-semibold mb-2">Card Title</div>
  <div className="text-foreground-60">Card description with muted text</div>
  <div className="mt-4 flex gap-2">
    <ModusButton color="primary">Primary Action</ModusButton>
    <ModusButton variant="borderless">Secondary</ModusButton>
  </div>
</div>

Form Input with Feedback

tsx

// ✅ CORRECT: Form input styling
<div>
  <ModusInputLabel label="Email" required />
  <ModusTextInput
    value={email}
    onInputChange={handleEmailChange}
    customClass={errors.email ? "border-destructive" : "border-default"}
  />
  {errors.email && (
    <ModusInputFeedback
      message={errors.email}
      type="error"
    />
  )}
</div>

Button States

tsx

// ✅ CORRECT: Button with hover states
<button className="
  bg-primary text-primary-foreground
  hover:bg-primary-80
  border-primary
  rounded-lg px-4 py-2
  transition-colors
">
  Click me
</button>

Text Hierarchy

tsx

// ✅ CORRECT: Text hierarchy with opacity
<div className="space-y-2">
  <div className="text-foreground text-2xl font-bold">Main Heading</div>
  <div className="text-foreground-80 text-lg">Subheading</div>
  <div className="text-foreground-60 text-base">Body text</div>
  <div className="text-muted-foreground-60 text-sm">Caption</div>
</div>

Common Mistakes to Avoid

Mistake 1: Using Tailwind Color Classes

tsx

// ❌ WRONG: Hardcoded Tailwind colors
<div className="border border-red-500">Error</div>
<div className="text-blue-600">Info</div>
<div className="bg-green-100">Success</div>

// ✅ CORRECT: Design system colors
<div className="border-destructive">Error</div>
<div className="text-primary">Info</div>
<div className="bg-success-20">Success</div>

Mistake 2: Using Tailwind Opacity Syntax

tsx

// ❌ WRONG: Tailwind opacity syntax doesn't work
<div className="text-foreground/80">Text</div>
<div className="bg-primary/60">Background</div>
<div className="border border-destructive/40">Border</div>

// ✅ CORRECT: Custom opacity utilities
<div className="text-foreground-80">Text</div>
<div className="bg-primary-60">Background</div>
<div className="border border-destructive-40">Border</div>

Mistake 3: Mixing Tailwind and Custom Utilities

tsx

// ❌ WRONG: Mixing incompatible patterns
<div className="border border-destructive/80">Mixed patterns</div>

// ✅ CORRECT: Use custom utilities consistently
<div className="border border-destructive-80">Consistent pattern</div>

Mistake 4: Using Inline Styles

tsx

// ❌ WRONG: Inline styles bypass design system
<div style={{ border: "1px solid var(--modus-wc-color-error)" }}>Error</div>
<div style={{ color: "rgba(0, 0, 0, 0.8)" }}>Text</div>

// ✅ CORRECT: Use utility classes
<div className="border-destructive">Error</div>
<div className="text-foreground-80">Text</div>

Migration Patterns

From Tailwind Default Borders

tsx

// Before: Tailwind defaults
<div className="border border-red-500">Error</div>
<div className="border-2 border-green-500">Success</div>

// After: Custom utilities
<div className="border-destructive">Error</div>
<div className="border-thick-success">Success</div>

From Tailwind Opacity Modifiers

tsx

// Before: Tailwind opacity (doesn't work)
<div className="text-foreground/80">Text</div>
<div className="bg-primary/60">Background</div>

// After: Custom opacity utilities
<div className="text-foreground-80">Text</div>
<div className="bg-primary-60">Background</div>

From Inline Styles

tsx

// Before: Inline styles
<div style={{ 
  border: "1px solid var(--modus-wc-color-error)",
  color: "rgba(0, 0, 0, 0.8)"
}}>Content</div>

// After: Utility classes
<div className="border-destructive text-foreground-80">Content</div>

Theme Compatibility

All custom utilities work with all 6 Modus themes:

•✅ Classic Light
•✅ Classic Dark
•✅ Modern Light
•✅ Modern Dark
•✅ Connect Light
•✅ Connect Dark

Colors automatically adapt when themes change - no code changes needed.

Implementation Location

Custom utilities are defined in:

•src/index.css - All border and opacity utilities

Testing Checklist

• Components use custom border utilities (not Tailwind colors)
• Opacity uses custom utilities (not /80 syntax)
• No hardcoded colors (hex, RGB, Tailwind defaults)
• Components work in all 6 themes
• Colors adapt when theme switches
• No inline styles for colors/borders

Related Files

•docs/tailwind-css-variables-problem.md - Detailed technical explanation
•src/index.css - Custom utility definitions
•.cursor/rules/border-usage-guidelines.mdc - Border usage rules
•.cursor/rules/modus-opacity-utilities-react.mdc - Opacity utilities rules
•.cursor/rules/modus-color-usage-react.mdc - Color usage rules

Quick Reference

Borders

•Use: border-destructive, border-success, border-warning, border-primary
•Don't use: border-red-500, border-green-500, border border-destructive

Opacity

•Use: text-foreground-80, bg-primary-60, border-destructive-40
•Don't use: text-foreground/80, bg-primary/60, border-destructive/40

Colors

•Use: text-foreground, bg-primary, text-destructive
•Don't use: text-gray-900, bg-blue-500, text-red-600