react-theme-system/src/styles/theme-fallbacks.css

A comprehensive React theme management system that enforces consistency, supports dark/light mode, and eliminates hardcoded styles

/* React Theme System - CSS Variables with Fallbacks */
/* This file provides CSS variables with fallbacks for graceful degradation */

/* System theme detection */
@media (prefers-color-scheme: dark) {
  :root {
    /* Dark theme defaults when system prefers dark */
    --color-primary: #60a5fa;
    --color-secondary: #818cf8;
    --color-accent: #34d399;
    --color-background: #0f172a;
    --color-surface: #1e293b;
    --color-text-primary: #f8fafc;
    --color-text-secondary: #cbd5e1;
    --color-text-disabled: #64748b;
    --color-border: #334155;
    --color-error: #f87171;
    --color-warning: #fbbf24;
    --color-success: #4ade80;
    --color-info: #60a5fa;
  }
}

@media (prefers-color-scheme: light) {
  :root {
    /* Light theme defaults when system prefers light */
    --color-primary: #4361ee;
    --color-secondary: #3f37c9;
    --color-accent: #4895ef;
    --color-background: #ffffff;
    --color-surface: #f8f9fa;
    --color-text-primary: #212529;
    --color-text-secondary: #6c757d;
    --color-text-disabled: #adb5bd;
    --color-border: #dee2e6;
    --color-error: #dc3545;
    --color-warning: #ffc107;
    --color-success: #28a745;
    --color-info: #17a2b8;
  }
}

/* Base fallbacks (light theme) */
:root {
  /* Colors */
  --color-primary: #4361ee;
  --color-secondary: #3f37c9;
  --color-accent: #4895ef;
  --color-background: #ffffff;
  --color-surface: #f8f9fa;
  --color-text-primary: #212529;
  --color-text-secondary: #6c757d;
  --color-text-disabled: #adb5bd;
  --color-border: #dee2e6;
  --color-error: #dc3545;
  --color-warning: #ffc107;
  --color-success: #28a745;
  --color-info: #17a2b8;

  /* Spacing */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 3rem;
  --spacing-xxl: 4rem;

  /* Typography */
  --font-family-primary: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-family-secondary: Georgia, "Times New Roman", serif;
  --font-family-mono: SFMono-Regular, Consolas, "Liberation Mono", Menlo, monospace;
  
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.875rem;
  --font-size-4xl: 2.25rem;
  
  --font-weight-light: 300;
  --font-weight-normal: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;
  
  --line-height-tight: 1.25;
  --line-height-normal: 1.5;
  --line-height-relaxed: 1.75;

  /* Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  --shadow-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
  --shadow-inner: inset 0 2px 4px 0 rgba(0, 0, 0, 0.06);
  --shadow-none: none;

  /* Border Radius */
  --radius-none: 0;
  --radius-sm: 0.125rem;
  --radius-md: 0.375rem;
  --radius-lg: 0.5rem;
  --radius-xl: 0.75rem;
  --radius-full: 9999px;

  /* Breakpoints */
  --breakpoint-sm: 640px;
  --breakpoint-md: 768px;
  --breakpoint-lg: 1024px;
  --breakpoint-xl: 1280px;
  --breakpoint-2xl: 1536px;

  /* Transitions */
  --transition-fast: 150ms ease-in-out;
  --transition-normal: 300ms ease-in-out;
  --transition-slow: 500ms ease-in-out;
  --transition-ease-in: ease-in;
  --transition-ease-out: ease-out;
  --transition-ease-in-out: ease-in-out;

  /* Z-Index */
  --z-index-hide: -1;
  --z-index-auto: 0;
  --z-index-base: 0;
  --z-index-docked: 10;
  --z-index-dropdown: 1000;
  --z-index-sticky: 1100;
  --z-index-banner: 1200;
  --z-index-overlay: 1300;
  --z-index-modal: 1400;
  --z-index-popover: 1500;
  --z-index-skip-link: 1600;
  --z-index-toast: 1700;
  --z-index-tooltip: 1800;
}

/* Dark theme overrides */
[data-theme="dark"] {
  /* Colors */
  --color-primary: #60a5fa;
  --color-secondary: #818cf8;
  --color-accent: #34d399;
  --color-background: #0f172a;
  --color-surface: #1e293b;
  --color-text-primary: #f8fafc;
  --color-text-secondary: #cbd5e1;
  --color-text-disabled: #64748b;
  --color-border: #334155;
  --color-error: #f87171;
  --color-warning: #fbbf24;
  --color-success: #4ade80;
  --color-info: #60a5fa;

  /* Shadows - darker for dark theme */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -1px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.4), 0 4px 6px -2px rgba(0, 0, 0, 0.3);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.4), 0 10px 10px -5px rgba(0, 0, 0, 0.3);
  --shadow-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.5);
  --shadow-inner: inset 0 2px 4px 0 rgba(0, 0, 0, 0.3);
}

/* Light theme explicit override */
[data-theme="light"] {
  /* Colors */
  --color-primary: #4361ee;
  --color-secondary: #3f37c9;
  --color-accent: #4895ef;
  --color-background: #ffffff;
  --color-surface: #f8f9fa;
  --color-text-primary: #212529;
  --color-text-secondary: #6c757d;
  --color-text-disabled: #adb5bd;
  --color-border: #dee2e6;
  --color-error: #dc3545;
  --color-warning: #ffc107;
  --color-success: #28a745;
  --color-info: #17a2b8;

  /* Shadows - lighter for light theme */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  --shadow-2xl: 0 25px 50px -12px rgba(0, 0, 0, 0.25);
  --shadow-inner: inset 0 2px 4px 0 rgba(0, 0, 0, 0.06);
}

/* Utility classes for common theme patterns */
.theme-transition {
  transition: color var(--transition-normal), background-color var(--transition-normal), border-color var(--transition-normal);
}

.theme-focus {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

.theme-focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
}

/* High contrast mode support */
@media (prefers-contrast: high) {
  :root {
    --color-primary: #0000ff;
    --color-secondary: #000080;
    --color-accent: #008000;
    --color-background: #ffffff;
    --color-surface: #f0f0f0;
    --color-text-primary: #000000;
    --color-text-secondary: #333333;
    --color-text-disabled: #666666;
    --color-border: #000000;
    --color-error: #ff0000;
    --color-warning: #ff8000;
    --color-success: #008000;
    --color-info: #0000ff;
  }
  
  [data-theme="dark"] {
    --color-primary: #ffff00;
    --color-secondary: #ffff80;
    --color-accent: #80ff80;
    --color-background: #000000;
    --color-surface: #1a1a1a;
    --color-text-primary: #ffffff;
    --color-text-secondary: #cccccc;
    --color-text-disabled: #999999;
    --color-border: #ffffff;
    --color-error: #ff8080;
    --color-warning: #ffcc80;
    --color-success: #80ff80;
    --color-info: #8080ff;
  }
}

/* Reduced motion support */
@media (prefers-reduced-motion: reduce) {
  :root {
    --transition-fast: 0ms;
    --transition-normal: 0ms;
    --transition-slow: 0ms;
  }
  
  * {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}