/**
 * ============================================
 * HOMESCHOOL QUIZ APP - DESIGN SYSTEM 2026
 * ============================================
 *
 * Calm, minimal, joyful educational interface
 * Following 2025-2026 best practices:
 * - Generous whitespace
 * - Soft, nature-inspired color palette
 * - AAA accessibility
 * - Perfect dark mode
 * - Subtle glassmorphism
 * - Smooth micro-interactions
 */

/* ==========================================
   CSS CUSTOM PROPERTIES - DESIGN TOKENS
   ========================================== */

:root {
  /* ===== CALM COLOR PALETTE ===== */
  /* Primary: Soft Blue-Green (Calming, trustworthy) */
  --color-primary-50: #f0fdf9;
  --color-primary-100: #ccfbef;
  --color-primary-200: #99f6e0;
  --color-primary-300: #5fe9ce;
  --color-primary-400: #2dd4b8;
  --color-primary-500: #4d9e93;  /* Main brand color */
  --color-primary-600: #3d8e83;
  --color-primary-700: #2f7a71;
  --color-primary-800: #26615a;
  --color-primary-900: #1e4d48;

  /* Neutral: Warm grays for calm reading */
  --color-neutral-50: #f8faf9;
  --color-neutral-100: #f1f4f3;
  --color-neutral-200: #e4e9e7;
  --color-neutral-300: #d1d8d6;
  --color-neutral-400: #9fa9a6;
  --color-neutral-500: #6b7673;
  --color-neutral-600: #535d5a;
  --color-neutral-700: #3f4744;
  --color-neutral-800: #2d3331;
  --color-neutral-900: #1a1f1d;

  /* Success: Soft Green (encouraging, growth) */
  --color-success-50: #f0fdf4;
  --color-success-100: #dcfce7;
  --color-success-500: #22c55e;
  --color-success-600: #16a34a;

  /* Warning: Warm Amber (attention, gentle) */
  --color-warning-50: #fffbeb;
  --color-warning-100: #fef3c7;
  --color-warning-500: #f59e0b;
  --color-warning-600: #d97706;

  /* Error: Soft Red (clear but not alarming) */
  --color-error-50: #fef2f2;
  --color-error-100: #fee2e2;
  --color-error-500: #ef4444;
  --color-error-600: #dc2626;

  /* ===== SEMANTIC TOKENS ===== */
  --color-background: var(--color-neutral-50);
  --color-surface: #ffffff;
  --color-surface-raised: #ffffff;
  --color-overlay: rgba(29, 47, 44, 0.05);

  --color-text-primary: var(--color-neutral-900);
  --color-text-secondary: var(--color-neutral-600);
  --color-text-tertiary: var(--color-neutral-500);
  --color-text-inverse: var(--color-neutral-50);

  --color-border: var(--color-neutral-200);
  --color-border-hover: var(--color-neutral-300);
  --color-border-focus: var(--color-primary-500);

  /* ===== TYPOGRAPHY ===== */
  /* Font families */
  --font-primary: -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'Segoe UI', system-ui, sans-serif;
  --font-reading: 'Georgia', 'Cambria', 'Times New Roman', serif;
  --font-mono: 'SF Mono', 'Monaco', 'Cascadia Code', 'Courier New', monospace;

  /* Dyslexia-friendly option */
  --font-dyslexic: 'OpenDyslexic', 'Comic Sans MS', sans-serif;

  /* Font sizes - Generous, readable scale */
  --text-xs: 0.75rem;     /* 12px */
  --text-sm: 0.875rem;    /* 14px */
  --text-base: 1rem;      /* 16px */
  --text-lg: 1.125rem;    /* 18px */
  --text-xl: 1.25rem;     /* 20px */
  --text-2xl: 1.5rem;     /* 24px */
  --text-3xl: 1.875rem;   /* 30px */
  --text-4xl: 2.25rem;    /* 36px */
  --text-5xl: 3rem;       /* 48px */

  /* Line heights - Increased for readability */
  --leading-tight: 1.25;
  --leading-normal: 1.6;
  --leading-relaxed: 1.8;
  --leading-loose: 2;

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

  /* ===== SPACING SCALE ===== */
  /* 4px base unit for consistency */
  --space-0: 0;
  --space-px: 1px;
  --space-0-5: 0.125rem;  /* 2px */
  --space-1: 0.25rem;     /* 4px */
  --space-2: 0.5rem;      /* 8px */
  --space-3: 0.75rem;     /* 12px */
  --space-4: 1rem;        /* 16px */
  --space-5: 1.25rem;     /* 20px */
  --space-6: 1.5rem;      /* 24px */
  --space-8: 2rem;        /* 32px */
  --space-10: 2.5rem;     /* 40px */
  --space-12: 3rem;       /* 48px */
  --space-16: 4rem;       /* 64px */
  --space-20: 5rem;       /* 80px */
  --space-24: 6rem;       /* 96px */

  /* ===== BORDER RADIUS ===== */
  --radius-none: 0;
  --radius-sm: 0.375rem;    /* 6px */
  --radius-md: 0.5rem;      /* 8px */
  --radius-lg: 0.75rem;     /* 12px */
  --radius-xl: 1rem;        /* 16px */
  --radius-2xl: 1.5rem;     /* 24px */
  --radius-3xl: 2rem;       /* 32px */
  --radius-full: 9999px;

  /* ===== SHADOWS - Soft, Natural ===== */
  --shadow-xs: 0 1px 2px 0 rgba(77, 158, 147, 0.05);
  --shadow-sm: 0 2px 4px 0 rgba(77, 158, 147, 0.08);
  --shadow-md: 0 4px 12px 0 rgba(77, 158, 147, 0.12);
  --shadow-lg: 0 8px 24px 0 rgba(77, 158, 147, 0.15);
  --shadow-xl: 0 12px 40px 0 rgba(77, 158, 147, 0.18);
  --shadow-2xl: 0 20px 60px 0 rgba(77, 158, 147, 0.22);

  /* Colored shadows for interactive elements */
  --shadow-primary: 0 4px 12px 0 rgba(77, 158, 147, 0.25);
  --shadow-success: 0 4px 12px 0 rgba(34, 197, 94, 0.25);
  --shadow-warning: 0 4px 12px 0 rgba(245, 158, 11, 0.25);
  --shadow-error: 0 4px 12px 0 rgba(239, 68, 68, 0.25);

  /* ===== GLASSMORPHISM ===== */
  --glass-background: rgba(255, 255, 255, 0.7);
  --glass-border: rgba(255, 255, 255, 0.3);
  --glass-shadow: 0 8px 32px 0 rgba(77, 158, 147, 0.1);
  --glass-blur: blur(12px);

  /* ===== TRANSITIONS & ANIMATIONS ===== */
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-bounce: 500ms cubic-bezier(0.34, 1.56, 0.64, 1);

  /* Spring physics for natural motion */
  --ease-spring: cubic-bezier(0.34, 1.56, 0.64, 1);
  --ease-smooth: cubic-bezier(0.4, 0, 0.2, 1);
  --ease-in-out: cubic-bezier(0.645, 0.045, 0.355, 1);

  /* ===== Z-INDEX SCALE ===== */
  --z-base: 0;
  --z-dropdown: 1000;
  --z-sticky: 1100;
  --z-fixed: 1200;
  --z-modal-backdrop: 1300;
  --z-modal: 1400;
  --z-popover: 1500;
  --z-toast: 1600;
  --z-tooltip: 1700;

  /* ===== CONTAINER WIDTHS ===== */
  --container-sm: 640px;
  --container-md: 768px;
  --container-lg: 1024px;
  --container-xl: 1280px;
  --container-2xl: 1536px;
}

/* ==========================================
   DARK MODE - System Preference by Default
   ========================================== */

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    /* Dark mode color palette */
    --color-background: #0f1413;
    --color-surface: #1a1f1d;
    --color-surface-raised: #2d3331;
    --color-overlay: rgba(255, 255, 255, 0.05);

    --color-text-primary: var(--color-neutral-50);
    --color-text-secondary: var(--color-neutral-300);
    --color-text-tertiary: var(--color-neutral-400);
    --color-text-inverse: var(--color-neutral-900);

    --color-border: var(--color-neutral-800);
    --color-border-hover: var(--color-neutral-700);

    /* Adjust primary colors for dark mode */
    --color-primary-500: #5fe9ce;
    --color-primary-600: #2dd4b8;

    /* Softer shadows in dark mode */
    --shadow-xs: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-sm: 0 2px 4px 0 rgba(0, 0, 0, 0.4);
    --shadow-md: 0 4px 12px 0 rgba(0, 0, 0, 0.5);
    --shadow-lg: 0 8px 24px 0 rgba(0, 0, 0, 0.6);
    --shadow-xl: 0 12px 40px 0 rgba(0, 0, 0, 0.7);

    /* Glassmorphism in dark mode */
    --glass-background: rgba(26, 31, 29, 0.7);
    --glass-border: rgba(255, 255, 255, 0.1);
  }
}

/* ==========================================
   HIGH CONTRAST MODE - Accessibility
   ========================================== */

[data-theme="high-contrast"] {
  --color-background: #ffffff;
  --color-surface: #ffffff;
  --color-text-primary: #000000;
  --color-text-secondary: #000000;
  --color-primary-500: #0000ff;
  --color-success-500: #008000;
  --color-warning-500: #ff8c00;
  --color-error-500: #ff0000;
  --color-border: #000000;

  /* High contrast shadows */
  --shadow-md: 0 0 0 2px #000000;
  --shadow-lg: 0 0 0 3px #000000;
}

@media (prefers-color-scheme: dark) {
  [data-theme="high-contrast"] {
    --color-background: #000000;
    --color-surface: #000000;
    --color-text-primary: #ffffff;
    --color-text-secondary: #ffffff;
    --color-primary-500: #00ffff;
    --color-success-500: #00ff00;
    --color-warning-500: #ffff00;
    --color-error-500: #ff00ff;
    --color-border: #ffffff;
  }
}

/* ==========================================
   REDUCED MOTION - Respect User Preferences
   ========================================== */

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* ==========================================
   BASE STYLES - Reset & Typography
   ========================================== */

*,
*::before,
*::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  -webkit-tap-highlight-color: transparent;
}

body {
  font-family: var(--font-primary);
  font-size: var(--text-base);
  line-height: var(--leading-normal);
  color: var(--color-text-primary);
  background-color: var(--color-background);
  transition: background-color var(--transition-base), color var(--transition-base);
  min-height: 100vh;
  overflow-x: hidden;
}

/* Dyslexia-friendly font option */
body.dyslexic-font {
  font-family: var(--font-dyslexic);
  letter-spacing: 0.05em;
  word-spacing: 0.16em;
}

/* ==========================================
   TYPOGRAPHY UTILITIES
   ========================================== */

h1, h2, h3, h4, h5, h6 {
  font-weight: var(--font-semibold);
  line-height: var(--leading-tight);
  color: var(--color-text-primary);
  margin-bottom: var(--space-4);
}

h1 { font-size: var(--text-4xl); letter-spacing: -0.02em; }
h2 { font-size: var(--text-3xl); letter-spacing: -0.015em; }
h3 { font-size: var(--text-2xl); }
h4 { font-size: var(--text-xl); }
h5 { font-size: var(--text-lg); }
h6 { font-size: var(--text-base); }

p {
  margin-bottom: var(--space-4);
  line-height: var(--leading-relaxed);
}

a {
  color: var(--color-primary-500);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--color-primary-600);
  text-decoration: underline;
}

a:focus-visible {
  outline: 2px solid var(--color-primary-500);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

/* ==========================================
   BUTTON SYSTEM - Calm, Accessible
   ========================================== */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  font-family: var(--font-primary);
  font-size: var(--text-base);
  font-weight: var(--font-medium);
  line-height: 1;
  border: none;
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all var(--transition-base);
  white-space: nowrap;
  user-select: none;
  position: relative;
  overflow: hidden;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
  pointer-events: none;
}

.btn:focus-visible {
  outline: 3px solid var(--color-primary-500);
  outline-offset: 2px;
}

/* Primary button - Main actions */
.btn-primary {
  background: linear-gradient(135deg, var(--color-primary-500) 0%, var(--color-primary-600) 100%);
  color: white;
  box-shadow: var(--shadow-primary);
}

.btn-primary:hover:not(:disabled) {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
}

.btn-primary:active:not(:disabled) {
  transform: translateY(0);
  box-shadow: var(--shadow-sm);
}

/* Secondary button - Less emphasis */
.btn-secondary {
  background-color: var(--color-surface);
  color: var(--color-text-primary);
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-sm);
}

.btn-secondary:hover:not(:disabled) {
  background-color: var(--color-neutral-100);
  border-color: var(--color-border-hover);
  box-shadow: var(--shadow-md);
}

/* Ghost button - Minimal */
.btn-ghost {
  background-color: transparent;
  color: var(--color-text-primary);
}

.btn-ghost:hover:not(:disabled) {
  background-color: var(--color-overlay);
}

/* Icon button - Square */
.btn-icon {
  padding: var(--space-3);
  width: 40px;
  height: 40px;
}

/* Button sizes */
.btn-sm {
  padding: var(--space-2) var(--space-4);
  font-size: var(--text-sm);
}

.btn-lg {
  padding: var(--space-4) var(--space-8);
  font-size: var(--text-lg);
}

/* ==========================================
   CARD SYSTEM - Soft, Elevated
   ========================================== */

.card {
  background-color: var(--color-surface);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  box-shadow: var(--shadow-md);
  border: 1px solid var(--color-border);
  transition: all var(--transition-base);
}

.card:hover {
  box-shadow: var(--shadow-lg);
  transform: translateY(-2px);
}

.card-glass {
  background: var(--glass-background);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: 1px solid var(--glass-border);
  box-shadow: var(--glass-shadow);
}

/* ==========================================
   FORM ELEMENTS - Accessible, Beautiful
   ========================================== */

input:not([type="checkbox"]):not([type="radio"]),
textarea,
select {
  width: 100%;
  padding: var(--space-3) var(--space-4);
  font-family: var(--font-primary);
  font-size: var(--text-base);
  line-height: var(--leading-normal);
  color: var(--color-text-primary);
  background-color: var(--color-surface);
  border: 1.5px solid var(--color-border);
  border-radius: var(--radius-lg);
  transition: all var(--transition-fast);
}

input:focus,
textarea:focus,
select:focus {
  outline: none;
  border-color: var(--color-primary-500);
  box-shadow: 0 0 0 3px rgba(77, 158, 147, 0.1);
}

/* ==========================================
   ACCESSIBILITY UTILITIES
   ========================================== */

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border-width: 0;
}

/* Skip to content link */
.skip-to-content {
  position: absolute;
  top: -100%;
  left: 0;
  background-color: var(--color-primary-500);
  color: white;
  padding: var(--space-4) var(--space-6);
  border-radius: var(--radius-lg);
  font-weight: var(--font-semibold);
  z-index: var(--z-tooltip);
  transition: top var(--transition-fast);
}

.skip-to-content:focus {
  top: var(--space-4);
}

/* ==========================================
   LOADING & SKELETON STATES
   ========================================== */

@keyframes skeleton-pulse {
  0%, 100% {
    opacity: 1;
  }
  50% {
    opacity: 0.5;
  }
}

.skeleton {
  background: linear-gradient(
    90deg,
    var(--color-neutral-200) 25%,
    var(--color-neutral-100) 50%,
    var(--color-neutral-200) 75%
  );
  background-size: 200% 100%;
  animation: skeleton-pulse 1.5s ease-in-out infinite;
  border-radius: var(--radius-md);
}

/* Spinner */
@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

.spinner {
  width: 40px;
  height: 40px;
  border: 3px solid var(--color-neutral-200);
  border-top-color: var(--color-primary-500);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

/* Continue in next file due to length... */