/* ============================================================
   Finance, Economics & Wealth Mastery System — Design System
   ============================================================ */

/* --- Custom Properties ------------------------------------ */
:root {
  /* Brand Colors */
  --color-primary: #3b82f6;
  --color-primary-dark: #1d4ed8;
  --color-primary-light: #93c5fd;
  --color-accent: #f59e0b;
  --color-accent-dark: #d97706;
  --color-success: #22c55e;
  --color-warning: #f97316;
  --color-danger: #ef4444;
  --color-info: #06b6d4;

  /* Mastery Level Colors */
  --mastery-0: #6b7280;
  --mastery-1: #9ca3af;
  --mastery-2: #fbbf24;
  --mastery-3: #f97316;
  --mastery-4: #84cc16;
  --mastery-5: #22c55e;
  --mastery-6: #14b8a6;
  --mastery-7: #3b82f6;
  --mastery-8: #8b5cf6;
  --mastery-9: #ec4899;

  /* Light Theme Surfaces */
  --bg-base: #f8fafc;
  --bg-surface: #ffffff;
  --bg-surface-2: #f1f5f9;
  --bg-surface-3: #e2e8f0;
  --bg-sidebar: #1e293b;
  --bg-sidebar-hover: #334155;
  --bg-sidebar-active: #3b82f6;

  /* Text */
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --text-inverse: #f8fafc;
  --text-sidebar: #cbd5e1;
  --text-sidebar-active: #ffffff;

  /* Borders */
  --border-subtle: #e2e8f0;
  --border-default: #cbd5e1;
  --border-strong: #94a3b8;

  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-5: 1.25rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-10: 2.5rem;
  --space-12: 3rem;
  --space-16: 4rem;

  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;
  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.5rem;
  --text-3xl: 1.875rem;
  --text-4xl: 2.25rem;
  --leading-tight: 1.25;
  --leading-normal: 1.5;
  --leading-relaxed: 1.75;
  --font-normal: 400;
  --font-medium: 500;
  --font-semibold: 600;
  --font-bold: 700;

  /* Shadows */
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
  --shadow-md: 0 4px 6px rgba(0,0,0,0.07), 0 2px 4px rgba(0,0,0,0.06);
  --shadow-lg: 0 10px 15px rgba(0,0,0,0.1), 0 4px 6px rgba(0,0,0,0.05);
  --shadow-xl: 0 20px 25px rgba(0,0,0,0.1), 0 10px 10px rgba(0,0,0,0.04);

  /* Radii */
  --radius-sm: 0.25rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  --radius-full: 9999px;

  /* Layout */
  --sidebar-width: 260px;
  --header-height: 60px;
  --content-max-width: 900px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;
}

/* --- Dark Mode -------------------------------------------- */
[data-theme="dark"] {
  --bg-base: #0f172a;
  --bg-surface: #1e293b;
  --bg-surface-2: #263348;
  --bg-surface-3: #334155;
  --bg-sidebar: #0a0f1e;
  --bg-sidebar-hover: #1e293b;
  --bg-sidebar-active: #3b82f6;

  --text-primary: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;

  --border-subtle: #1e293b;
  --border-default: #334155;
  --border-strong: #475569;

  --shadow-sm: 0 1px 2px rgba(0,0,0,0.3);
  --shadow-md: 0 4px 6px rgba(0,0,0,0.4), 0 2px 4px rgba(0,0,0,0.3);
  --shadow-lg: 0 10px 15px rgba(0,0,0,0.5), 0 4px 6px rgba(0,0,0,0.3);
}

/* --- Reset & Base ----------------------------------------- */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

html {
  font-size: 16px;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

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

a { color: var(--color-primary); text-decoration: none; }
a:hover { text-decoration: underline; }
img { max-width: 100%; height: auto; display: block; }
button { cursor: pointer; font-family: inherit; }
input, select, textarea { font-family: inherit; font-size: inherit; }

/* --- Layout Shell ----------------------------------------- */
.app-shell {
  display: flex;
  min-height: 100vh;
}

/* --- Sidebar ---------------------------------------------- */
.sidebar {
  width: var(--sidebar-width);
  min-height: 100vh;
  background: var(--bg-sidebar);
  display: flex;
  flex-direction: column;
  position: fixed;
  top: 0;
  left: 0;
  z-index: 100;
  transition: transform var(--transition-base);
}

.sidebar-header {
  padding: var(--space-6) var(--space-5);
  border-bottom: 1px solid rgba(255,255,255,0.07);
}

.sidebar-logo {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  color: var(--text-inverse);
  text-decoration: none;
}

.sidebar-logo-icon {
  font-size: 1.75rem;
  line-height: 1;
}

.sidebar-logo-text {
  font-weight: var(--font-bold);
  font-size: var(--text-sm);
  line-height: 1.3;
  letter-spacing: -0.01em;
}

.sidebar-logo-text span {
  display: block;
  color: var(--color-accent);
  font-size: var(--text-xs);
  font-weight: var(--font-normal);
  letter-spacing: 0.05em;
  text-transform: uppercase;
}

.sidebar-nav {
  flex: 1;
  padding: var(--space-4) 0;
  overflow-y: auto;
}

.nav-section-title {
  font-size: var(--text-xs);
  font-weight: var(--font-semibold);
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  padding: var(--space-3) var(--space-5) var(--space-2);
  margin-top: var(--space-4);
}

.nav-item {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-5);
  color: var(--text-sidebar);
  font-size: var(--text-sm);
  font-weight: var(--font-medium);
  border-radius: 0;
  transition: background var(--transition-fast), color var(--transition-fast);
  cursor: pointer;
  border: none;
  background: none;
  width: 100%;
  text-align: left;
  text-decoration: none;
}

.nav-item:hover {
  background: var(--bg-sidebar-hover);
  color: var(--text-sidebar-active);
  text-decoration: none;
}

.nav-item.active {
  background: var(--bg-sidebar-active);
  color: var(--text-sidebar-active);
}

.nav-item-icon {
  font-size: 1rem;
  width: 1.25rem;
  text-align: center;
  flex-shrink: 0;
}

.nav-item-badge {
  margin-left: auto;
  font-size: var(--text-xs);
  font-weight: var(--font-semibold);
  padding: 1px 7px;
  border-radius: var(--radius-full);
  background: rgba(255,255,255,0.1);
  color: var(--text-muted);
}

.nav-item.active .nav-item-badge {
  background: rgba(255,255,255,0.2);
  color: white;
}

/* Module progress in sidebar */
.nav-module-item {
  padding: var(--space-2) var(--space-5) var(--space-2) calc(var(--space-5) + 1rem);
}

.nav-module-progress {
  height: 3px;
  background: rgba(255,255,255,0.1);
  border-radius: var(--radius-full);
  margin-top: var(--space-1);
  overflow: hidden;
}

.nav-module-progress-fill {
  height: 100%;
  border-radius: var(--radius-full);
  background: var(--color-accent);
  transition: width var(--transition-slow);
}

.sidebar-footer {
  padding: var(--space-4) var(--space-5);
  border-top: 1px solid rgba(255,255,255,0.07);
}

/* --- Main Content ----------------------------------------- */
.main-content {
  flex: 1;
  margin-left: var(--sidebar-width);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* --- Top Header ------------------------------------------- */
.topbar {
  height: var(--header-height);
  background: var(--bg-surface);
  border-bottom: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  padding: 0 var(--space-8);
  gap: var(--space-4);
  position: sticky;
  top: 0;
  z-index: 50;
  box-shadow: var(--shadow-sm);
}

.topbar-breadcrumb {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.topbar-breadcrumb-sep { color: var(--text-muted); }

.topbar-title {
  font-weight: var(--font-semibold);
  font-size: var(--text-base);
  color: var(--text-primary);
}

.topbar-actions {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

/* Search */
.search-box {
  display: flex;
  align-items: center;
  gap: var(--space-2);
  background: var(--bg-surface-2);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--space-2) var(--space-4);
  width: 240px;
  transition: border-color var(--transition-fast), width var(--transition-base);
}

.search-box:focus-within {
  border-color: var(--color-primary);
  width: 320px;
}

.search-box input {
  border: none;
  background: none;
  outline: none;
  font-size: var(--text-sm);
  color: var(--text-primary);
  width: 100%;
}

.search-box input::placeholder { color: var(--text-muted); }

/* Theme toggle */
.theme-toggle {
  width: 36px;
  height: 36px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-default);
  background: var(--bg-surface);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1rem;
  cursor: pointer;
  transition: background var(--transition-fast), border-color var(--transition-fast);
}

.theme-toggle:hover {
  background: var(--bg-surface-2);
  border-color: var(--border-strong);
}

/* --- Page Content ----------------------------------------- */
.page-content {
  flex: 1;
  padding: var(--space-8);
  max-width: calc(var(--content-max-width) + var(--space-16));
}

/* --- Dashboard -------------------------------------------- */
.dashboard-hero {
  background: linear-gradient(135deg, var(--color-primary) 0%, #1d4ed8 100%);
  border-radius: var(--radius-xl);
  padding: var(--space-10) var(--space-8);
  color: white;
  margin-bottom: var(--space-8);
  position: relative;
  overflow: hidden;
}

.dashboard-hero::before {
  content: '';
  position: absolute;
  top: -50%;
  right: -10%;
  width: 400px;
  height: 400px;
  background: radial-gradient(circle, rgba(255,255,255,0.08) 0%, transparent 70%);
  border-radius: 50%;
}

.dashboard-hero-eyebrow {
  font-size: var(--text-sm);
  font-weight: var(--font-semibold);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  opacity: 0.8;
  margin-bottom: var(--space-3);
}

.dashboard-hero-title {
  font-size: var(--text-3xl);
  font-weight: var(--font-bold);
  line-height: var(--leading-tight);
  margin-bottom: var(--space-4);
}

.dashboard-hero-subtitle {
  font-size: var(--text-base);
  opacity: 0.85;
  max-width: 560px;
  line-height: var(--leading-relaxed);
  margin-bottom: var(--space-8);
}

.dashboard-hero-stats {
  display: flex;
  gap: var(--space-8);
  flex-wrap: wrap;
}

.hero-stat {
  display: flex;
  flex-direction: column;
  gap: 2px;
}

.hero-stat-value {
  font-size: var(--text-2xl);
  font-weight: var(--font-bold);
}

.hero-stat-label {
  font-size: var(--text-xs);
  opacity: 0.7;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* --- Section Headers -------------------------------------- */
.section-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-5);
}

.section-title {
  font-size: var(--text-xl);
  font-weight: var(--font-bold);
  color: var(--text-primary);
}

.section-subtitle {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  margin-top: var(--space-1);
}

.section-link {
  font-size: var(--text-sm);
  font-weight: var(--font-medium);
  color: var(--color-primary);
}

/* --- Module Cards Grid ------------------------------------ */
.modules-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--space-5);
  margin-bottom: var(--space-8);
}

.module-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  cursor: pointer;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast), border-color var(--transition-fast);
  position: relative;
  overflow: hidden;
}

.module-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: var(--module-color, var(--color-primary));
}

.module-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-lg);
  border-color: var(--module-color, var(--color-primary));
  text-decoration: none;
}

.module-card-header {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  margin-bottom: var(--space-4);
}

.module-icon {
  font-size: 2rem;
  line-height: 1;
}

.module-mastery-badge {
  font-size: var(--text-xs);
  font-weight: var(--font-semibold);
  padding: var(--space-1) var(--space-3);
  border-radius: var(--radius-full);
  background: var(--bg-surface-2);
  color: var(--text-secondary);
}

.module-mastery-badge.has-progress {
  background: color-mix(in srgb, var(--mastery-color) 15%, transparent);
  color: var(--mastery-color);
}

.module-number {
  font-size: var(--text-xs);
  font-weight: var(--font-semibold);
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--space-2);
}

.module-title {
  font-size: var(--text-lg);
  font-weight: var(--font-bold);
  color: var(--text-primary);
  margin-bottom: var(--space-2);
  line-height: var(--leading-tight);
}

.module-subtitle {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  line-height: var(--leading-normal);
  margin-bottom: var(--space-5);
}

.module-meta {
  display: flex;
  align-items: center;
  gap: var(--space-4);
  font-size: var(--text-xs);
  color: var(--text-muted);
  margin-bottom: var(--space-4);
}

.module-meta-item {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.module-progress-bar {
  height: 6px;
  background: var(--bg-surface-3);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.module-progress-fill {
  height: 100%;
  border-radius: var(--radius-full);
  background: var(--module-color, var(--color-primary));
  transition: width var(--transition-slow);
}

/* --- Stats Row -------------------------------------------- */
.stats-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: var(--space-4);
  margin-bottom: var(--space-8);
}

.stat-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: var(--space-5) var(--space-6);
  text-align: left;
}

.stat-label {
  font-size: var(--text-xs);
  font-weight: var(--font-semibold);
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin-bottom: var(--space-2);
}

.stat-value {
  font-size: var(--text-3xl);
  font-weight: var(--font-bold);
  color: var(--text-primary);
  line-height: 1;
  margin-bottom: var(--space-1);
}

.stat-change {
  font-size: var(--text-sm);
  color: var(--text-muted);
}

.stat-change.positive { color: var(--color-success); }
.stat-change.negative { color: var(--color-danger); }

/* --- Buttons ---------------------------------------------- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
  border-radius: var(--radius-lg);
  font-size: var(--text-sm);
  font-weight: var(--font-semibold);
  border: none;
  cursor: pointer;
  transition: all var(--transition-fast);
  text-decoration: none;
  white-space: nowrap;
  line-height: 1;
}

.btn:hover { text-decoration: none; }

.btn-primary {
  background: var(--color-primary);
  color: white;
}

.btn-primary:hover { background: var(--color-primary-dark); color: white; }

.btn-secondary {
  background: var(--bg-surface-2);
  color: var(--text-primary);
  border: 1px solid var(--border-default);
}

.btn-secondary:hover { background: var(--bg-surface-3); }

.btn-ghost {
  background: transparent;
  color: var(--text-secondary);
}

.btn-ghost:hover { background: var(--bg-surface-2); color: var(--text-primary); }

.btn-accent {
  background: var(--color-accent);
  color: white;
}

.btn-accent:hover { background: var(--color-accent-dark); color: white; }

.btn-sm { padding: var(--space-2) var(--space-3); font-size: var(--text-xs); }
.btn-lg { padding: var(--space-4) var(--space-8); font-size: var(--text-base); border-radius: var(--radius-xl); }

/* --- Badges ----------------------------------------------- */
.badge {
  display: inline-flex;
  align-items: center;
  gap: var(--space-1);
  padding: 2px var(--space-2);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: var(--font-semibold);
}

.badge-primary { background: #dbeafe; color: #1d4ed8; }
.badge-success { background: #dcfce7; color: #15803d; }
.badge-warning { background: #fef9c3; color: #a16207; }
.badge-danger { background: #fee2e2; color: #b91c1c; }
.badge-neutral { background: var(--bg-surface-3); color: var(--text-secondary); }

[data-theme="dark"] .badge-primary { background: rgba(59,130,246,0.2); color: #93c5fd; }
[data-theme="dark"] .badge-success { background: rgba(34,197,94,0.2); color: #86efac; }
[data-theme="dark"] .badge-warning { background: rgba(234,179,8,0.2); color: #fde047; }
[data-theme="dark"] .badge-danger { background: rgba(239,68,68,0.2); color: #fca5a5; }

/* --- Progress Bar ----------------------------------------- */
.progress-bar {
  height: 8px;
  background: var(--bg-surface-3);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.progress-fill {
  height: 100%;
  border-radius: var(--radius-full);
  background: var(--color-primary);
  transition: width 0.6s ease;
}

/* --- Mastery Level Display --------------------------------- */
.mastery-level {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-full);
  font-size: var(--text-sm);
  font-weight: var(--font-semibold);
}

.mastery-dots {
  display: flex;
  gap: 4px;
}

.mastery-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--border-default);
  transition: background var(--transition-fast);
}

.mastery-dot.filled {
  background: var(--mastery-color, var(--color-primary));
}

/* --- Cards ------------------------------------------------ */
.card {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
}

.card-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: var(--space-5);
}

.card-title {
  font-size: var(--text-lg);
  font-weight: var(--font-bold);
  color: var(--text-primary);
}

/* --- Lesson Page ------------------------------------------ */
.lesson-container {
  max-width: var(--content-max-width);
  margin: 0 auto;
}

.lesson-hero {
  margin-bottom: var(--space-8);
}

.lesson-meta-row {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  margin-bottom: var(--space-4);
  flex-wrap: wrap;
}

.lesson-title {
  font-size: var(--text-3xl);
  font-weight: var(--font-bold);
  line-height: var(--leading-tight);
  margin-bottom: var(--space-3);
}

.lesson-subtitle {
  font-size: var(--text-lg);
  color: var(--text-secondary);
  line-height: var(--leading-relaxed);
  margin-bottom: var(--space-6);
}

.lesson-key-questions {
  background: linear-gradient(135deg, rgba(59,130,246,0.08), rgba(139,92,246,0.08));
  border: 1px solid rgba(59,130,246,0.2);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  margin-bottom: var(--space-8);
}

.lesson-key-questions h3 {
  font-size: var(--text-sm);
  font-weight: var(--font-semibold);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-primary);
  margin-bottom: var(--space-4);
}

.lesson-key-questions ul {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.lesson-key-questions li {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  font-size: var(--text-base);
  color: var(--text-secondary);
  line-height: var(--leading-normal);
}

.lesson-key-questions li::before {
  content: '→';
  color: var(--color-primary);
  flex-shrink: 0;
  font-weight: var(--font-bold);
}

/* --- Topic Card ------------------------------------------- */
.topic-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  margin-bottom: var(--space-5);
  overflow: hidden;
  transition: box-shadow var(--transition-fast);
}

.topic-card:hover { box-shadow: var(--shadow-md); }

.topic-card-header {
  padding: var(--space-5) var(--space-6);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-4);
}

.topic-card-title {
  font-size: var(--text-base);
  font-weight: var(--font-semibold);
  color: var(--text-primary);
}

.topic-card-level {
  font-size: var(--text-xs);
  padding: 2px var(--space-2);
  border-radius: var(--radius-full);
  background: var(--bg-surface-2);
  color: var(--text-muted);
  white-space: nowrap;
}

.topic-card-chevron {
  transition: transform var(--transition-fast);
  color: var(--text-muted);
  flex-shrink: 0;
}

.topic-card.open .topic-card-chevron {
  transform: rotate(180deg);
}

.topic-card-body {
  display: none;
  padding: 0 var(--space-6) var(--space-6);
  border-top: 1px solid var(--border-subtle);
}

.topic-card.open .topic-card-body { display: block; }

/* --- Depth Sections --------------------------------------- */
.depth-section {
  margin-top: var(--space-5);
}

.depth-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--space-4);
  margin-top: var(--space-4);
}

@media (max-width: 640px) {
  .depth-grid { grid-template-columns: 1fr; }
}

.depth-item {
  background: var(--bg-surface-2);
  border-radius: var(--radius-lg);
  padding: var(--space-4);
}

.depth-item-label {
  font-size: var(--text-xs);
  font-weight: var(--font-semibold);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--color-primary);
  margin-bottom: var(--space-2);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.depth-item-content {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  line-height: var(--leading-relaxed);
}

.depth-item.full-width {
  grid-column: 1 / -1;
}

.expert-insight {
  background: linear-gradient(135deg, rgba(139,92,246,0.08), rgba(236,72,153,0.08));
  border: 1px solid rgba(139,92,246,0.2);
  border-radius: var(--radius-xl);
  padding: var(--space-5) var(--space-6);
  margin-top: var(--space-5);
}

.expert-insight-label {
  font-size: var(--text-xs);
  font-weight: var(--font-semibold);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: #8b5cf6;
  margin-bottom: var(--space-3);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.expert-insight-content {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  line-height: var(--leading-relaxed);
  font-style: italic;
}

/* Misconceptions */
.misconceptions-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  margin-top: var(--space-3);
}

.misconceptions-list li {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  font-size: var(--text-sm);
  color: var(--text-secondary);
  line-height: var(--leading-relaxed);
  background: rgba(239,68,68,0.05);
  border: 1px solid rgba(239,68,68,0.15);
  border-radius: var(--radius-lg);
  padding: var(--space-3) var(--space-4);
}

.misconceptions-list li::before {
  content: '✗';
  color: var(--color-danger);
  font-weight: bold;
  flex-shrink: 0;
}

/* Key Terms */
.key-terms {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
  margin-top: var(--space-3);
}

.key-term {
  display: inline-flex;
  align-items: center;
  padding: var(--space-1) var(--space-3);
  background: var(--bg-surface-2);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-full);
  font-size: var(--text-xs);
  font-weight: var(--font-medium);
  color: var(--text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.key-term:hover {
  background: var(--color-primary);
  color: white;
  border-color: var(--color-primary);
}

/* --- Quiz ------------------------------------------------- */
.quiz-container {
  max-width: 680px;
}

.quiz-question {
  font-size: var(--text-lg);
  font-weight: var(--font-semibold);
  color: var(--text-primary);
  line-height: var(--leading-normal);
  margin-bottom: var(--space-6);
}

.quiz-options {
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
  margin-bottom: var(--space-6);
}

.quiz-option {
  display: flex;
  align-items: flex-start;
  gap: var(--space-4);
  padding: var(--space-4) var(--space-5);
  background: var(--bg-surface);
  border: 2px solid var(--border-default);
  border-radius: var(--radius-xl);
  cursor: pointer;
  transition: all var(--transition-fast);
  font-size: var(--text-sm);
  line-height: var(--leading-normal);
  color: var(--text-primary);
}

.quiz-option:hover {
  border-color: var(--color-primary);
  background: rgba(59,130,246,0.05);
}

.quiz-option.selected {
  border-color: var(--color-primary);
  background: rgba(59,130,246,0.08);
}

.quiz-option.correct {
  border-color: var(--color-success);
  background: rgba(34,197,94,0.08);
}

.quiz-option.incorrect {
  border-color: var(--color-danger);
  background: rgba(239,68,68,0.08);
}

.quiz-option-letter {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--bg-surface-2);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--text-xs);
  font-weight: var(--font-bold);
  flex-shrink: 0;
  transition: all var(--transition-fast);
}

.quiz-option.selected .quiz-option-letter {
  background: var(--color-primary);
  color: white;
}

.quiz-option.correct .quiz-option-letter {
  background: var(--color-success);
  color: white;
}

.quiz-option.incorrect .quiz-option-letter {
  background: var(--color-danger);
  color: white;
}

.quiz-explanation {
  background: var(--bg-surface-2);
  border-left: 4px solid var(--color-primary);
  border-radius: var(--radius-md);
  padding: var(--space-4) var(--space-5);
  font-size: var(--text-sm);
  color: var(--text-secondary);
  line-height: var(--leading-relaxed);
  animation: slideDown 0.3s ease;
}

@keyframes slideDown {
  from { opacity: 0; transform: translateY(-8px); }
  to { opacity: 1; transform: translateY(0); }
}

/* --- Modal ------------------------------------------------ */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  backdrop-filter: blur(4px);
  z-index: 200;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-4);
  opacity: 0;
  transition: opacity var(--transition-base);
}

.modal-overlay.visible { opacity: 1; }

.modal {
  background: var(--bg-surface);
  border-radius: var(--radius-xl);
  width: 100%;
  max-width: 560px;
  max-height: 90vh;
  overflow-y: auto;
  box-shadow: var(--shadow-xl);
  transform: scale(0.95);
  transition: transform var(--transition-base);
}

.modal-overlay.visible .modal { transform: scale(1); }

.modal-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-6);
  border-bottom: 1px solid var(--border-subtle);
}

.modal-title { font-size: var(--text-xl); font-weight: var(--font-bold); }

.modal-close {
  width: 32px;
  height: 32px;
  border-radius: var(--radius-lg);
  border: none;
  background: var(--bg-surface-2);
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  font-size: 1.25rem;
  color: var(--text-muted);
  line-height: 1;
}

.modal-close:hover { background: var(--bg-surface-3); color: var(--text-primary); }

.modal-body { padding: var(--space-6); }

/* --- Toast Notifications ---------------------------------- */
.toast-container {
  position: fixed;
  bottom: var(--space-6);
  right: var(--space-6);
  z-index: 300;
  display: flex;
  flex-direction: column;
  gap: var(--space-3);
}

.toast {
  background: var(--bg-surface);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-xl);
  padding: var(--space-4) var(--space-5);
  box-shadow: var(--shadow-lg);
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-size: var(--text-sm);
  color: var(--text-primary);
  min-width: 280px;
  max-width: 400px;
  animation: slideInRight 0.3s ease, fadeOut 0.3s ease 2.7s forwards;
}

@keyframes slideInRight {
  from { opacity: 0; transform: translateX(20px); }
  to { opacity: 1; transform: translateX(0); }
}

@keyframes fadeOut {
  to { opacity: 0; transform: translateX(20px); }
}

.toast-icon { font-size: 1.25rem; flex-shrink: 0; }
.toast-message { flex: 1; }

/* --- Mastery Selector ------------------------------------- */
.mastery-selector {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: var(--space-2);
}

.mastery-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-1);
  padding: var(--space-3) var(--space-2);
  background: var(--bg-surface-2);
  border: 2px solid transparent;
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all var(--transition-fast);
  font-size: var(--text-xs);
  font-weight: var(--font-medium);
  color: var(--text-secondary);
}

.mastery-btn:hover {
  border-color: var(--mastery-color);
  background: color-mix(in srgb, var(--mastery-color) 10%, transparent);
  color: var(--text-primary);
}

.mastery-btn.active {
  border-color: var(--mastery-color);
  background: color-mix(in srgb, var(--mastery-color) 15%, transparent);
  color: var(--text-primary);
}

.mastery-btn-number {
  font-size: var(--text-lg);
  font-weight: var(--font-bold);
  color: var(--mastery-color);
}

/* --- Learning Path Card ----------------------------------- */
.learning-path-card {
  background: var(--bg-surface);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: var(--space-6);
  cursor: pointer;
  transition: all var(--transition-fast);
}

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

.learning-paths-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: var(--space-4);
  margin-bottom: var(--space-8);
}

.path-icon {
  font-size: 2rem;
  margin-bottom: var(--space-3);
}

.path-title {
  font-weight: var(--font-bold);
  font-size: var(--text-base);
  margin-bottom: var(--space-2);
}

.path-desc {
  font-size: var(--text-sm);
  color: var(--text-secondary);
  line-height: var(--leading-normal);
  margin-bottom: var(--space-4);
}

.path-modules {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

/* --- Utility Classes -------------------------------------- */
.flex { display: flex; }
.flex-col { flex-direction: column; }
.items-center { align-items: center; }
.justify-between { justify-content: space-between; }
.gap-2 { gap: var(--space-2); }
.gap-3 { gap: var(--space-3); }
.gap-4 { gap: var(--space-4); }
.mt-2 { margin-top: var(--space-2); }
.mt-4 { margin-top: var(--space-4); }
.mt-6 { margin-top: var(--space-6); }
.mb-4 { margin-bottom: var(--space-4); }
.mb-6 { margin-bottom: var(--space-6); }
.mb-8 { margin-bottom: var(--space-8); }
.text-sm { font-size: var(--text-sm); }
.text-muted { color: var(--text-muted); }
.font-semibold { font-weight: var(--font-semibold); }
.font-bold { font-weight: var(--font-bold); }
.hidden { display: none !important; }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0,0,0,0); }

/* --- Mobile ----------------------------------------------- */
.menu-toggle {
  display: none;
  width: 36px;
  height: 36px;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border-default);
  background: var(--bg-surface);
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
  cursor: pointer;
  color: var(--text-secondary);
}

@media (max-width: 768px) {
  .sidebar {
    transform: translateX(-100%);
  }

  .sidebar.open {
    transform: translateX(0);
  }

  .main-content {
    margin-left: 0;
  }

  .menu-toggle {
    display: flex;
  }

  .search-box {
    width: 160px;
  }

  .search-box:focus-within {
    width: 200px;
  }

  .modules-grid {
    grid-template-columns: 1fr;
  }

  .stats-row {
    grid-template-columns: 1fr 1fr;
  }

  .page-content {
    padding: var(--space-4);
  }

  .dashboard-hero {
    padding: var(--space-6);
  }

  .dashboard-hero-title {
    font-size: var(--text-2xl);
  }

  .mastery-selector {
    grid-template-columns: repeat(5, 1fr);
  }

  .depth-grid {
    grid-template-columns: 1fr;
  }
}

/* --- Tools / Calculator Forms ----------------------------- */
.form-group {
  margin-bottom: var(--space-4);
}

.form-label {
  display: block;
  font-size: var(--text-sm);
  font-weight: var(--font-medium);
  color: var(--text-secondary);
  margin-bottom: var(--space-1);
}

.form-input {
  width: 100%;
  padding: var(--space-2) var(--space-3);
  background: var(--bg-surface-2);
  border: 1px solid var(--border-default);
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  color: var(--text-primary);
  font-family: inherit;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
  box-sizing: border-box;
}

.form-input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.12);
}

input[type="range"].form-input {
  padding: var(--space-1) 0;
  background: transparent;
  border: none;
  box-shadow: none;
  cursor: pointer;
}

input[type="range"].form-input::-webkit-slider-track {
  height: 4px;
  background: var(--border-default);
  border-radius: var(--radius-full);
}

input[type="range"].form-input::-webkit-slider-thumb {
  -webkit-appearance: none;
  width: 16px;
  height: 16px;
  border-radius: 50%;
  background: var(--color-primary);
  margin-top: -6px;
  cursor: pointer;
  box-shadow: 0 1px 3px rgba(0,0,0,0.2);
}

.form-hint {
  font-size: var(--text-xs);
  color: var(--text-muted);
  margin-top: var(--space-1);
}

/* --- Scrollbar -------------------------------------------- */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: var(--border-default); border-radius: var(--radius-full); }
::-webkit-scrollbar-thumb:hover { background: var(--border-strong); }

/* --- Transitions ------------------------------------------ */
.fade-in {
  animation: fadeIn 0.3s ease forwards;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

/* --- Page Transitions ------------------------------------- */
.page { display: none; }
.page.active { display: block; animation: fadeIn 0.25s ease; }

/* --- Sidebar overlay for mobile -------------------------- */
.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  z-index: 99;
}

.sidebar-overlay.visible { display: block; }