/**
 * CSS Custom Properties (Variables)
 * Centralized theme configuration for consistent styling
 */

:root {
  /* Color Palette */
  --color-primary: #2c5aa0;
  --color-primary-dark: #1a365d;
  --color-primary-light: #667eea;
  --color-secondary: #764ba2;
  --color-accent: #007bff;
  --color-accent-hover: #0056b3;

  /* Text Colors */
  --color-text-primary: #333;
  --color-text-secondary: #666;
  --color-text-muted: #6c757d;
  --color-text-light: #495057;

  /* Background Colors */
  --color-bg-primary: #ffffff;
  --color-bg-secondary: #f8f9fa;
  --color-bg-tertiary: #f5f5f5;
  --color-bg-gradient-start: #f8f9fa;
  --color-bg-gradient-end: #e9ecef;

  /* Border Colors */
  --color-border-light: #e1e5e9;
  --color-border-medium: #dee2e6;
  --color-border-dark: #ddd;
  --color-border-focus: #007bff;

  /* Focus Styles */
  --focus-ring-color: #007bff;
  --focus-ring-width: 3px;
  --focus-ring-offset: 2px;
  --focus-ring-style: solid;
  --focus-ring-opacity: 0.5;
  --focus-bg-highlight: rgba(0, 123, 255, 0.1);
  --focus-animation-duration: 0.2s;

  /* Difficulty Colors */
  --color-difficulty-easy-bg: #d4edda;
  --color-difficulty-easy-text: #155724;
  --color-difficulty-easy-border: #c3e6cb;

  --color-difficulty-medium-bg: #fff3cd;
  --color-difficulty-medium-text: #856404;
  --color-difficulty-medium-border: #ffeaa7;

  --color-difficulty-hard-bg: #f8d7da;
  --color-difficulty-hard-text: #721c24;
  --color-difficulty-hard-border: #f5c6cb;

  /* Hero Gradient */
  --hero-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --hero-text-color: #ffffff;

  /* Spacing */
  --spacing-1: 1px;
  --spacing-2: 2px;
  --spacing-3: 3px;
  --spacing-xs: 4px;
  --spacing-5: 5px;
  --spacing-6: 6px;
  --spacing-sm: 8px;
  --spacing-10: 10px;
  --spacing-md: 15px;
  --spacing-lg: 20px;
  --spacing-xl: 25px;
  --spacing-2xl: 30px;
  --spacing-36: 36px;
  --spacing-3xl: 40px;
  --spacing-44: 44px;
  --spacing-48: 48px;
  --spacing-4xl: 60px;
  --spacing-5xl: 100px;

  /* Layout-specific spacing */
  --min-touch-target: 44px;
  --min-card-width: 320px;
  --scroll-offset: 100px;

  /* Border Radius */
  --radius-sm: 3px;
  --radius-md: 4px;
  --radius-lg: 6px;
  --radius-xl: 12px;

  /* Border Widths */
  --border-width: 1px;
  --border-width-thick: 2px;
  --border-width-thicker: 4px;

  /* Shadows */
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.12);
  --shadow-lg: 0 8px 25px rgba(0, 0, 0, 0.15);
  --shadow-hover: 0 8px 25px rgba(0, 0, 0, 0.15);

  /* Typography - Fluid Responsive Scale using clamp() */
  /* Scales smoothly between mobile (320px) and desktop (1200px) viewports */
  /* Formula: clamp(min, preferred with vw, max) */
  /* Base font size: minimum 16px (1rem) for accessibility */

  /* Small labels, captions - scales from 10px to 12px */
  --font-size-xs: clamp(0.625rem, 0.55rem + 0.25vw, 0.75rem);

  /* Meta info, small text - scales from 12px to 14px */
  --font-size-sm: clamp(0.75rem, 0.7rem + 0.25vw, 0.875rem);

  /* Body text - scales from 16px to 18px (minimum 16px for accessibility) */
  --font-size-base: clamp(1rem, 0.95rem + 0.25vw, 1.125rem);

  /* Slightly larger body text - scales from 17px to 20px */
  --font-size-md: clamp(1.063rem, 1rem + 0.3vw, 1.25rem);

  /* Lead paragraphs, large body - scales from 18px to 22px */
  --font-size-lg: clamp(1.125rem, 1.05rem + 0.35vw, 1.375rem);

  /* h4 headings - scales from 20px to 26px */
  --font-size-xl: clamp(1.25rem, 1.15rem + 0.5vw, 1.625rem);

  /* h3 headings - scales from 24px to 32px */
  --font-size-2xl: clamp(1.5rem, 1.35rem + 0.75vw, 2rem);

  /* h2 headings - scales from 28px to 40px */
  --font-size-3xl: clamp(1.75rem, 1.5rem + 1.25vw, 2.5rem);

  /* h1 headings - scales from 32px to 48px */
  --font-size-4xl: clamp(2rem, 1.7rem + 1.5vw, 3rem);

  /* Hero/display headings - scales from 36px to 60px */
  --font-size-5xl: clamp(2.25rem, 1.8rem + 2.25vw, 3.75rem);

  /* Font weights */
  --font-weight-normal: 400;
  --font-weight-medium: 500;
  --font-weight-semibold: 600;
  --font-weight-bold: 700;

  /* Line heights - Optimized for readability */
  --line-height-tight: 1.25;    /* For large headings */
  --line-height-snug: 1.375;    /* For medium headings */
  --line-height-normal: 1.5;    /* For body text */
  --line-height-relaxed: 1.625; /* For long-form content */
  --line-height-loose: 1.75;    /* For very spacious reading */

  /* Letter spacing */
  --letter-spacing-tight: -0.025em;
  --letter-spacing-normal: 0;
  --letter-spacing-wide: 0.025em;
  --letter-spacing-wider: 0.05em;

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-normal: 0.2s ease;
  --transition-slow: 0.3s ease;

  /* Layout */
  --max-width-content: 800px;
  --max-width-container: 1200px;

  /* Z-index layers */
  --z-index-base: 1;
  --z-index-dropdown: 100;
  --z-index-modal: 1000;

  /* Breakpoints (for JS usage) */
  --breakpoint-mobile: 480px;
  --breakpoint-tablet: 600px;
  --breakpoint-desktop: 768px;
  --breakpoint-wide: 1024px;
}

/* Dark mode support */
@media (prefers-color-scheme: dark) {
  :root {
    /* Background Colors */
    --color-bg-primary: #1a1a1a;
    --color-bg-secondary: #2d2d2d;
    --color-bg-tertiary: #3d3d3d;
    --color-bg-gradient-start: #2d2d2d;
    --color-bg-gradient-end: #1a1a1a;

    /* Text Colors */
    --color-text-primary: #e0e0e0;
    --color-text-secondary: #b0b0b0;
    --color-text-muted: #9ca3af;
    --color-text-light: #d1d5db;

    /* Primary Colors (adjusted for dark backgrounds) */
    --color-primary: #4a9eff;
    --color-primary-dark: #3b82f6;
    --color-primary-light: #818cf8;
    --color-secondary: #a78bfa;
    --color-accent: #60a5fa;
    --color-accent-hover: #3b82f6;

    /* Border Colors */
    --color-border-light: #404040;
    --color-border-medium: #505050;
    --color-border-dark: #606060;
    --color-border-focus: #60a5fa;

    /* Focus Styles */
    --focus-ring-color: #60a5fa;
    --focus-ring-width: 3px;
    --focus-ring-offset: 2px;
    --focus-ring-style: solid;
    --focus-ring-opacity: 0.6;
    --focus-bg-highlight: rgba(96, 165, 250, 0.15);
    --focus-animation-duration: 0.2s;

    /* Difficulty Colors (adjusted for dark mode) */
    --color-difficulty-easy-bg: #1e3a2e;
    --color-difficulty-easy-text: #86efac;
    --color-difficulty-easy-border: #2d5a3f;

    --color-difficulty-medium-bg: #3a2e1e;
    --color-difficulty-medium-text: #fcd34d;
    --color-difficulty-medium-border: #5a4a2d;

    --color-difficulty-hard-bg: #3a1e1e;
    --color-difficulty-hard-text: #fca5a5;
    --color-difficulty-hard-border: #5a2d2d;

    /* Hero Gradient (adjusted for dark mode) */
    --hero-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --hero-text-color: #ffffff;

    /* Shadows (softer for dark mode) */
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
    --shadow-lg: 0 8px 25px rgba(0, 0, 0, 0.5);
    --shadow-hover: 0 8px 25px rgba(0, 0, 0, 0.5);
  }
}

/* Manual dark mode override (when user clicks toggle) */
[data-theme="dark"] {
  /* Background Colors */
  --color-bg-primary: #1a1a1a;
  --color-bg-secondary: #2d2d2d;
  --color-bg-tertiary: #3d3d3d;
  --color-bg-gradient-start: #2d2d2d;
  --color-bg-gradient-end: #1a1a1a;

  /* Text Colors */
  --color-text-primary: #e0e0e0;
  --color-text-secondary: #b0b0b0;
  --color-text-muted: #9ca3af;
  --color-text-light: #d1d5db;

  /* Primary Colors (adjusted for dark backgrounds) */
  --color-primary: #4a9eff;
  --color-primary-dark: #3b82f6;
  --color-primary-light: #818cf8;
  --color-secondary: #a78bfa;
  --color-accent: #60a5fa;
  --color-accent-hover: #3b82f6;

  /* Border Colors */
  --color-border-light: #404040;
  --color-border-medium: #505050;
  --color-border-dark: #606060;
  --color-border-focus: #60a5fa;

  /* Focus Styles */
  --focus-ring-color: #60a5fa;
  --focus-ring-width: 3px;
  --focus-ring-offset: 2px;
  --focus-ring-style: solid;
  --focus-ring-opacity: 0.6;
  --focus-bg-highlight: rgba(96, 165, 250, 0.15);
  --focus-animation-duration: 0.2s;

  /* Difficulty Colors (adjusted for dark mode) */
  --color-difficulty-easy-bg: #1e3a2e;
  --color-difficulty-easy-text: #86efac;
  --color-difficulty-easy-border: #2d5a3f;

  --color-difficulty-medium-bg: #3a2e1e;
  --color-difficulty-medium-text: #fcd34d;
  --color-difficulty-medium-border: #5a4a2d;

  --color-difficulty-hard-bg: #3a1e1e;
  --color-difficulty-hard-text: #fca5a5;
  --color-difficulty-hard-border: #5a2d2d;

  /* Hero Gradient (adjusted for dark mode) */
  --hero-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --hero-text-color: #ffffff;

  /* Shadows (softer for dark mode) */
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 8px 25px rgba(0, 0, 0, 0.5);
  --shadow-hover: 0 8px 25px rgba(0, 0, 0, 0.5);
}

/* Manual light mode override (when user clicks toggle to force light) */
[data-theme="light"] {
  /* Force light mode colors even if system prefers dark */
  --color-bg-primary: #ffffff;
  --color-bg-secondary: #f8f9fa;
  --color-bg-tertiary: #f5f5f5;
  --color-bg-gradient-start: #f8f9fa;
  --color-bg-gradient-end: #e9ecef;

  --color-text-primary: #333;
  --color-text-secondary: #666;
  --color-text-muted: #6c757d;
  --color-text-light: #495057;

  --color-primary: #2c5aa0;
  --color-primary-dark: #1a365d;
  --color-primary-light: #667eea;
  --color-secondary: #764ba2;
  --color-accent: #007bff;
  --color-accent-hover: #0056b3;

  --color-border-light: #e1e5e9;
  --color-border-medium: #dee2e6;
  --color-border-dark: #ddd;
  --color-border-focus: #007bff;

  --focus-ring-color: #007bff;
  --focus-ring-width: 3px;
  --focus-ring-offset: 2px;
  --focus-ring-style: solid;
  --focus-ring-opacity: 0.5;
  --focus-bg-highlight: rgba(0, 123, 255, 0.1);
  --focus-animation-duration: 0.2s;

  --color-difficulty-easy-bg: #d4edda;
  --color-difficulty-easy-text: #155724;
  --color-difficulty-easy-border: #c3e6cb;

  --color-difficulty-medium-bg: #fff3cd;
  --color-difficulty-medium-text: #856404;
  --color-difficulty-medium-border: #ffeaa7;

  --color-difficulty-hard-bg: #f8d7da;
  --color-difficulty-hard-text: #721c24;
  --color-difficulty-hard-border: #f5c6cb;

  --hero-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);

  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.12);
  --shadow-lg: 0 8px 25px rgba(0, 0, 0, 0.15);
  --shadow-hover: 0 8px 25px rgba(0, 0, 0, 0.15);
}

/* High contrast mode support */
@media (prefers-contrast: high) {
  :root {
    --color-border-light: #000;
    --color-border-medium: #000;
    --shadow-sm: none;
    --shadow-md: none;
    --shadow-lg: none;
  }
}

/* Reduced motion support */
@media (prefers-reduced-motion: reduce) {
  :root {
    --transition-fast: 0s;
    --transition-normal: 0s;
    --transition-slow: 0s;
  }
}