/* ============================================================
   AP Physics C E&M — Glassmorphism Study Guide
   style.css — All styles in one file
   ============================================================ */

/* --------------------------------------------------
   1. CSS Custom Properties (Light Theme)
   -------------------------------------------------- */
:root {
  --glass-bg-light: rgba(255, 255, 255, 0.08);
  --glass-bg: rgba(255, 255, 255, 0.15);
  --glass-bg-heavy: rgba(255, 255, 255, 0.25);
  --glass-blur-light: blur(8px);
  --glass-blur: blur(16px);
  --glass-blur-strong: blur(32px);
  --glass-border: 1px solid rgba(255, 255, 255, 0.18);
  --glass-border-subtle: 1px solid rgba(255, 255, 255, 0.10);
  --glass-radius: 12px;
  --glass-radius-sm: 8px;
  --glass-radius-lg: 20px;
  --glass-shadow: 0 4px 30px rgba(0, 0, 0, 0.1);
  --glass-shadow-elevated: 0 8px 40px rgba(0, 0, 0, 0.15);

  --primary: #4f6ef7;
  --primary-hover: #3d5bd9;
  --primary-light: rgba(79, 110, 247, 0.12);
  --secondary: #7c4dff;
  --secondary-light: rgba(124, 77, 255, 0.12);
  --accent: #00bcd4;
  --text: #1a1a2e;
  --text-secondary: #555570;
  --text-muted: #8888a0;
  --success: #4caf50;
  --success-light: rgba(76, 175, 80, 0.12);
  --warning: #ff9800;
  --warning-light: rgba(255, 152, 0, 0.12);
  --danger: #ef5350;
  --danger-light: rgba(239, 83, 80, 0.10);

  --bg-gradient-1: #e8ecf1;
  --bg-gradient-2: #d4dbe6;
  --bg-gradient-3: #c8d6e5;
  --bg-orb-1: rgba(79, 110, 247, 0.12);
  --bg-orb-2: rgba(124, 77, 255, 0.10);
  --bg-orb-3: rgba(0, 188, 212, 0.08);

  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', 'SF Mono', 'Fira Code', monospace;
  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.25rem;
  --text-xl: 1.75rem;
  --text-2xl: 2.25rem;

  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;

  --navbar-height: 64px;
  --sidebar-width: 260px;
  --content-max-width: 900px;
  --card-padding: 1.5rem;
  --card-gap: 1.25rem;

  --transition-fast: 0.15s ease;
  --transition-normal: 0.25s ease;
  --transition-slow: 0.4s ease;
}

/* --------------------------------------------------
   2. Dark Theme
   -------------------------------------------------- */
[data-theme="dark"] {
  --glass-bg-light: rgba(255, 255, 255, 0.04);
  --glass-bg: rgba(255, 255, 255, 0.08);
  --glass-bg-heavy: rgba(255, 255, 255, 0.14);
  --glass-border: 1px solid rgba(255, 255, 255, 0.12);
  --glass-border-subtle: 1px solid rgba(255, 255, 255, 0.07);
  --glass-shadow: 0 4px 30px rgba(0, 0, 0, 0.3);
  --glass-shadow-elevated: 0 8px 40px rgba(0, 0, 0, 0.4);

  --primary: #7b93ff;
  --primary-hover: #9aafff;
  --primary-light: rgba(123, 147, 255, 0.12);
  --secondary: #b388ff;
  --secondary-light: rgba(179, 136, 255, 0.12);
  --text: #e8e8f0;
  --text-secondary: #9999aa;
  --text-muted: #666680;
  --success: #66bb6a;
  --success-light: rgba(102, 187, 106, 0.12);

  --bg-gradient-1: #0a0a1a;
  --bg-gradient-2: #0f0f2a;
  --bg-gradient-3: #1a1a3a;
  --bg-orb-1: rgba(123, 147, 255, 0.08);
  --bg-orb-2: rgba(179, 136, 255, 0.06);
  --bg-orb-3: rgba(0, 188, 212, 0.05);
}

/* --------------------------------------------------
   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: 1.7;
  color: var(--text);
  background: linear-gradient(135deg, var(--bg-gradient-1), var(--bg-gradient-2), var(--bg-gradient-3));
  background-attachment: fixed;
  min-height: 100vh;
  overflow-x: hidden;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

h1, h2, h3, h4 { font-weight: 700; line-height: 1.3; color: var(--text); }
h1 { font-size: var(--text-2xl); letter-spacing: -0.02em; }
h2 { font-size: var(--text-xl); letter-spacing: -0.01em; }
h3 { font-size: var(--text-lg); }
h4 { font-size: var(--text-base); }

p + p { margin-top: var(--space-md); }
ul, ol { padding-left: 1.5rem; }
li + li { margin-top: var(--space-xs); }

code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  background: var(--primary-light);
  color: var(--primary);
  padding: 0.1em 0.4em;
  border-radius: 4px;
}

:focus-visible { outline: 2px solid var(--primary); outline-offset: 2px; border-radius: 4px; }
::selection { background: var(--primary-light); color: var(--primary); }

/* --------------------------------------------------
   4. Animated Background Orbs
   -------------------------------------------------- */
.bg-orbs {
  position: fixed; inset: 0; pointer-events: none; z-index: 0; overflow: hidden;
}
.bg-orb {
  position: absolute; border-radius: 50%; filter: blur(80px);
  animation: orb-float 20s infinite ease-in-out;
}
.bg-orb:nth-child(1) {
  width: 500px; height: 500px; background: var(--bg-orb-1);
  top: -10%; left: -5%; animation-delay: 0s; animation-duration: 25s;
}
.bg-orb:nth-child(2) {
  width: 400px; height: 400px; background: var(--bg-orb-2);
  top: 50%; right: -8%; animation-delay: -8s; animation-duration: 22s;
}
.bg-orb:nth-child(3) {
  width: 350px; height: 350px; background: var(--bg-orb-3);
  bottom: -10%; left: 30%; animation-delay: -15s; animation-duration: 28s;
}
@keyframes orb-float {
  0%, 100% { transform: translate(0, 0) scale(1); }
  25% { transform: translate(40px, -30px) scale(1.08); }
  50% { transform: translate(-20px, 20px) scale(0.95); }
  75% { transform: translate(-35px, -15px) scale(1.05); }
}

/* --------------------------------------------------
   5. Layout
   -------------------------------------------------- */
.app-shell {
  display: flex; gap: 0; position: relative; z-index: 1; padding-top: var(--navbar-height);
}
.main-content {
  flex: 1; min-width: 0; max-width: var(--content-max-width);
  margin: 0 auto; padding: var(--space-2xl) var(--space-xl); margin-left: var(--sidebar-width);
}

/* --------------------------------------------------
   6. Glass Navbar
   -------------------------------------------------- */
.glass-nav {
  position: fixed; top: 0; left: 0; right: 0; height: var(--navbar-height);
  background: var(--glass-bg-heavy);
  backdrop-filter: var(--glass-blur-strong);
  -webkit-backdrop-filter: var(--glass-blur-strong);
  border-bottom: var(--glass-border);
  box-shadow: var(--glass-shadow);
  z-index: 100;
  display: flex; align-items: center; padding: 0 var(--space-xl); gap: var(--space-md);
}
.nav-brand {
  font-weight: 700; font-size: var(--text-base); color: var(--text);
  white-space: nowrap; display: flex; align-items: center; gap: var(--space-sm);
}
.nav-brand .brand-icon { font-size: 1.3em; }
.nav-links {
  display: flex; align-items: center; gap: var(--space-xs); flex: 1;
  justify-content: center; overflow-x: auto; scrollbar-width: none;
}
.nav-links::-webkit-scrollbar { display: none; }
.nav-link {
  display: inline-flex; align-items: center; gap: 4px; padding: 6px 12px;
  border-radius: var(--glass-radius-sm); font-size: var(--text-sm); font-weight: 500;
  color: var(--text-secondary); white-space: nowrap; transition: all var(--transition-fast);
  background: transparent; border: none; cursor: pointer; font-family: var(--font-sans);
}
.nav-link:hover, .nav-link:focus-visible { color: var(--text); background: var(--glass-bg); }
.nav-link.active { color: var(--primary); background: var(--primary-light); font-weight: 600; }
.nav-link .unit-badge {
  font-size: 0.7em; font-weight: 700; background: var(--primary-light);
  color: var(--primary); padding: 1px 5px; border-radius: 4px; margin-right: 2px;
}
.nav-actions { display: flex; align-items: center; gap: var(--space-sm); }
.search-wrapper { position: relative; display: flex; align-items: center; }
.search-input {
  width: 180px; padding: 6px 12px 6px 32px; border-radius: var(--glass-radius-sm);
  border: var(--glass-border); background: var(--glass-bg-light); color: var(--text);
  font-family: var(--font-sans); font-size: var(--text-sm); transition: all var(--transition-fast);
}
.search-input:focus {
  outline: none; border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-light); width: 240px;
}
.search-input::placeholder { color: var(--text-muted); }
.search-icon {
  position: absolute; left: 10px; color: var(--text-muted); font-size: var(--text-sm); pointer-events: none;
}
.btn-icon {
  display: inline-flex; align-items: center; justify-content: center;
  width: 36px; height: 36px; border-radius: var(--glass-radius-sm);
  border: var(--glass-border); background: var(--glass-bg-light);
  color: var(--text); cursor: pointer; font-size: var(--text-lg); transition: all var(--transition-fast);
}
.btn-icon:hover { background: var(--glass-bg); box-shadow: var(--glass-shadow); }
.mobile-menu-btn { display: none; }

/* --------------------------------------------------
   7. Glass Sidebar
   -------------------------------------------------- */
.sidebar {
  position: fixed; top: var(--navbar-height); left: 0;
  width: var(--sidebar-width); height: calc(100vh - var(--navbar-height));
  overflow-y: auto; padding: var(--space-lg);
  background: var(--glass-bg-heavy);
  backdrop-filter: var(--glass-blur-strong);
  -webkit-backdrop-filter: var(--glass-blur-strong);
  border-right: var(--glass-border); box-shadow: var(--glass-shadow);
  z-index: 50; transition: transform var(--transition-normal);
}
.sidebar-title {
  font-size: var(--text-sm); font-weight: 600; text-transform: uppercase;
  letter-spacing: 0.05em; color: var(--text-muted); margin-bottom: var(--space-md);
}
.sidebar-toc { list-style: none; padding: 0; }
.sidebar-toc li { margin: 0; }
.sidebar-toc a {
  display: block; padding: 6px 12px; border-radius: 6px; font-size: var(--text-sm);
  color: var(--text-secondary); transition: all var(--transition-fast);
  border-left: 2px solid transparent;
}
.sidebar-toc a:hover { color: var(--text); background: var(--glass-bg); }
.sidebar-toc a.active {
  color: var(--primary); background: var(--primary-light);
  border-left-color: var(--primary); font-weight: 600;
}
.sidebar-backdrop { display: none; }

/* --------------------------------------------------
   8. Glass Components
   -------------------------------------------------- */
.glass-card {
  background: var(--glass-bg);
  backdrop-filter: var(--glass-blur);
  -webkit-backdrop-filter: var(--glass-blur);
  border: var(--glass-border); border-radius: var(--glass-radius);
  box-shadow: var(--glass-shadow); padding: var(--card-padding);
  transition: box-shadow var(--transition-normal), transform var(--transition-fast);
  margin-bottom: var(--card-gap);
}
.glass-card:hover { box-shadow: var(--glass-shadow-elevated); }

.section-header {
  display: flex; align-items: center; gap: var(--space-md); cursor: pointer;
  user-select: none; padding-bottom: var(--space-md);
  border-bottom: var(--glass-border-subtle); margin-bottom: var(--space-md);
}
.section-header h2 { flex: 1; font-size: var(--text-lg); margin: 0; }
.section-header .progress-check {
  width: 20px; height: 20px; cursor: pointer; accent-color: var(--primary); flex-shrink: 0;
}
.collapse-toggle {
  background: none; border: none; color: var(--text-muted); cursor: pointer;
  font-size: var(--text-sm); padding: 4px; transition: transform var(--transition-fast);
  line-height: 1; font-family: var(--font-sans);
}
.collapse-toggle:hover { color: var(--text); }
.content-section.collapsed .collapse-toggle { transform: rotate(-90deg); }
.content-section.collapsed .section-body { display: none; }

.glass-btn {
  display: inline-flex; align-items: center; gap: var(--space-sm);
  padding: 8px 18px; border-radius: var(--glass-radius-sm);
  font-family: var(--font-sans); font-size: var(--text-sm); font-weight: 600;
  cursor: pointer; transition: all var(--transition-fast); text-decoration: none;
  border: var(--glass-border); background: var(--glass-bg-light); color: var(--text);
}
.glass-btn:hover {
  background: var(--glass-bg); box-shadow: var(--glass-shadow);
  transform: translateY(-1px); color: var(--text);
}
.glass-btn--primary { background: var(--primary); color: #fff; border-color: var(--primary); }
.glass-btn--primary:hover { background: var(--primary-hover); color: #fff; }

.glass-badge {
  display: inline-flex; align-items: center; padding: 3px 10px;
  border-radius: 100px; font-size: var(--text-xs); font-weight: 600;
  background: var(--primary-light); color: var(--primary);
  border: 1px solid rgba(79, 110, 247, 0.2);
}

.callout {
  padding: var(--space-md) var(--space-lg); border-radius: var(--glass-radius-sm);
  margin: var(--space-lg) 0; font-size: var(--text-sm); line-height: 1.6; border-left: 4px solid;
}
.callout--tip { background: var(--primary-light); border-color: var(--primary); }
.callout--warning { background: var(--warning-light); border-color: var(--warning); }
.callout--danger { background: var(--danger-light); border-color: var(--danger); }
.callout--success { background: var(--success-light); border-color: var(--success); }
.callout strong {
  display: block; margin-bottom: var(--space-xs); font-size: var(--text-sm);
  text-transform: uppercase; letter-spacing: 0.03em;
}

/* Progress */
.progress-bar-wrapper {
  display: flex; align-items: center; gap: var(--space-md); margin-bottom: var(--space-xl);
}
.progress-bar {
  flex: 1; height: 8px; border-radius: 100px; background: var(--glass-bg);
  overflow: hidden; border: var(--glass-border-subtle);
}
.progress-fill {
  height: 100%; background: linear-gradient(90deg, var(--primary), var(--secondary));
  border-radius: 100px; transition: width var(--transition-slow); width: 0%;
}
.progress-label {
  font-size: var(--text-sm); font-weight: 600; color: var(--text-secondary); white-space: nowrap;
}

/* --------------------------------------------------
   9. Practice Blocks
   -------------------------------------------------- */
.practice-block { border-left: 3px solid var(--secondary); }
.practice-header { display: flex; align-items: center; gap: var(--space-md); margin-bottom: var(--space-md); }
.practice-header h3 { margin: 0; font-size: var(--text-base); }
.practice-question { font-size: var(--text-base); line-height: 1.7; }
.solution { margin-top: var(--space-lg); }
.solution summary { list-style: none; display: inline-flex; }
.solution summary::-webkit-details-marker { display: none; }
.solution-content {
  margin-top: var(--space-md); padding: var(--space-lg);
  background: var(--glass-bg-light); border-radius: var(--glass-radius-sm);
  border: var(--glass-border-subtle); font-size: var(--text-sm);
}
.solution-content .step {
  margin-bottom: var(--space-sm); padding-left: var(--space-md);
  border-left: 2px solid var(--primary-light);
}

/* --------------------------------------------------
   10. Landing Page
   -------------------------------------------------- */
.hero { text-align: center; padding: var(--space-2xl) 0 var(--space-xl); }
.hero h1 {
  font-size: 2.5rem; font-weight: 800; letter-spacing: -0.03em;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
}
.hero .subtitle {
  margin-top: var(--space-md); font-size: var(--text-lg);
  color: var(--text-secondary); max-width: 600px; margin-inline: auto;
}
.exam-meta { margin-top: var(--space-lg); display: flex; justify-content: center; gap: var(--space-xl); flex-wrap: wrap; }
.exam-meta .meta-item { display: flex; flex-direction: column; align-items: center; gap: var(--space-xs); }
.meta-item .meta-value { font-size: var(--text-xl); font-weight: 700; color: var(--primary); }
.meta-item .meta-label { font-size: var(--text-xs); color: var(--text-muted); text-transform: uppercase; letter-spacing: 0.05em; }

.unit-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: var(--card-gap); margin: var(--space-2xl) 0;
}
.unit-card {
  display: flex; flex-direction: column; gap: var(--space-md); cursor: pointer;
  transition: all var(--transition-normal); text-decoration: none;
}
.unit-card:hover { transform: translateY(-3px); box-shadow: var(--glass-shadow-elevated); }
.unit-card .card-top { display: flex; align-items: center; justify-content: space-between; }
.unit-card .unit-number {
  font-size: var(--text-xs); font-weight: 700; color: var(--primary);
  text-transform: uppercase; letter-spacing: 0.05em;
}
.unit-card .unit-weight {
  font-size: var(--text-xs); font-weight: 600; color: var(--text-muted);
  background: var(--glass-bg); padding: 2px 8px; border-radius: 100px;
}
.unit-card h2 { font-size: var(--text-lg); margin: 0; color: var(--text); }
.unit-card .topic-preview { font-size: var(--text-sm); color: var(--text-secondary); line-height: 1.5; flex: 1; }
.card-progress { height: 4px; background: var(--glass-bg); border-radius: 100px; overflow: hidden; }
.card-progress-fill { height: 100%; background: var(--primary); border-radius: 100px; transition: width var(--transition-slow); width: 0%; }
.unit-card .card-footer { display: flex; align-items: center; justify-content: space-between; }
.progress-text { font-size: var(--text-xs); color: var(--text-muted); }

.shortcut-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: var(--space-sm); margin-top: var(--space-md);
}
.shortcut-item { display: flex; align-items: center; gap: var(--space-md); padding: var(--space-sm) 0; }
.shortcut-item kbd {
  display: inline-flex; align-items: center; justify-content: center;
  min-width: 28px; height: 28px; padding: 0 6px; background: var(--glass-bg);
  border: var(--glass-border); border-radius: 4px; font-family: var(--font-mono);
  font-size: var(--text-xs); font-weight: 600; color: var(--text);
  box-shadow: 0 1px 2px rgba(0,0,0,0.1);
}
.shortcut-item .shortcut-desc { font-size: var(--text-sm); color: var(--text-secondary); }
.site-footer { text-align: center; padding: var(--space-xl); font-size: var(--text-xs); color: var(--text-muted); }

.page-landing .main-content { margin-left: 0; max-width: 1000px; }
.page-landing .sidebar { display: none; }

/* --------------------------------------------------
   11. Utilities
   -------------------------------------------------- */
.hidden { display: none !important; }
.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0;
}
.text-center { text-align: center; }
.text-muted { color: var(--text-muted); }
.mt-md { margin-top: var(--space-md); }
.mb-md { margin-bottom: var(--space-md); }

/* Skip */
.skip-link {
  position: fixed; top: -100%; left: var(--space-md); z-index: 200;
  padding: var(--space-sm) var(--space-lg); background: var(--primary);
  color: white; border-radius: var(--glass-radius-sm); font-weight: 600;
  font-size: var(--text-sm); transition: top var(--transition-fast);
}
.skip-link:focus { top: var(--space-md); }

/* --------------------------------------------------
   12. MathJax
   -------------------------------------------------- */
mjx-container { overflow-x: auto; overflow-y: hidden; max-width: 100%; }
.equation-block {
  margin: var(--space-lg) 0; padding: var(--space-md) var(--space-lg);
  background: var(--glass-bg-light); border-radius: var(--glass-radius-sm);
  border: var(--glass-border-subtle); text-align: center; overflow-x: auto;
}

/* --------------------------------------------------
   13. Animation
   -------------------------------------------------- */
@keyframes fadeInUp {
  from { opacity: 0; transform: translateY(12px); }
  to { opacity: 1; transform: translateY(0); }
}

/* --------------------------------------------------
   14. Responsive — Tablet
   -------------------------------------------------- */
@media (max-width: 768px) {
  :root { --sidebar-width: 0px; --card-padding: 1.25rem; }
  .main-content { margin-left: 0; padding: var(--space-lg) var(--space-md); }
  .mobile-menu-btn { display: flex; }
  .nav-links {
    display: none; position: absolute; top: var(--navbar-height); left: 0; right: 0;
    flex-direction: column; background: var(--glass-bg-heavy);
    backdrop-filter: var(--glass-blur-strong); -webkit-backdrop-filter: var(--glass-blur-strong);
    border-bottom: var(--glass-border); padding: var(--space-md);
    box-shadow: var(--glass-shadow-elevated); z-index: 99;
  }
  .nav-links.open { display: flex; }
  .sidebar {
    transform: translateX(-100%); width: 280px; box-shadow: var(--glass-shadow-elevated);
  }
  .sidebar.open { transform: translateX(0); }
  .sidebar-backdrop {
    display: none; position: fixed; inset: 0; top: var(--navbar-height);
    background: rgba(0,0,0,0.3); z-index: 49;
  }
  .sidebar-backdrop.open { display: block; }
}

/* --------------------------------------------------
   15. Responsive — Mobile
   -------------------------------------------------- */
@media (max-width: 480px) {
  :root { --card-padding: 1rem; --card-gap: 0.75rem; }
  .glass-nav { padding: 0 var(--space-md); }
  .search-input { width: 100px; }
  .search-input:focus { width: 140px; }
  .unit-grid { grid-template-columns: 1fr; }
}

/* --------------------------------------------------
   16. Accessibility
   -------------------------------------------------- */
@media (prefers-reduced-transparency: reduce) {
  .glass-card, .glass-nav, .sidebar {
    background: rgba(255, 255, 255, 0.92); backdrop-filter: none; -webkit-backdrop-filter: none;
  }
  [data-theme="dark"] .glass-card,
  [data-theme="dark"] .glass-nav,
  [data-theme="dark"] .sidebar { background: rgba(20, 20, 40, 0.95); }
}
@media (prefers-contrast: more) {
  .glass-card, .glass-nav, .sidebar { border: 2px solid rgba(0, 0, 0, 0.3); }
  [data-theme="dark"] .glass-card,
  [data-theme="dark"] .glass-nav,
  [data-theme="dark"] .sidebar { border: 2px solid rgba(255, 255, 255, 0.3); }
  :focus-visible { outline-width: 3px; }
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .bg-orb { animation: none; }
  .glass-card, .glass-btn, .nav-link { transition: none; }
  .unit-card:hover { transform: none; }
}

/* --------------------------------------------------
   17. MCQ & Practice Page Styles
   -------------------------------------------------- */

/* -- Practice page header & scoreboard -- */
.practice-page-header {
  display: flex; align-items: center; justify-content: space-between;
  flex-wrap: wrap; gap: var(--space-md); margin-bottom: var(--space-xl);
}
.practice-scoreboard {
  display: flex; gap: var(--space-lg); align-items: center;
}
.score-item {
  display: flex; flex-direction: column; align-items: center;
}
.score-value {
  font-size: var(--text-xl); font-weight: 700; color: var(--primary);
}
.score-label {
  font-size: var(--text-xs); color: var(--text-muted); text-transform: uppercase;
}

/* -- Practice sub-navigation tabs -- */
.practice-tabs {
  display: flex; gap: var(--space-xs); margin-bottom: var(--space-xl);
  overflow-x: auto; padding-bottom: var(--space-xs);
}
.practice-tab {
  padding: 8px 18px; border-radius: var(--glass-radius-sm);
  font-size: var(--text-sm); font-weight: 600;
  background: var(--glass-bg-light); color: var(--text-secondary);
  border: var(--glass-border); cursor: pointer;
  white-space: nowrap; transition: all var(--transition-fast);
  font-family: var(--font-sans);
}
.practice-tab:hover { background: var(--glass-bg); color: var(--text); }
.practice-tab.active {
  background: var(--primary); color: #fff; border-color: var(--primary);
}

/* -- Practice section visibility -- */
.practice-section.hidden { display: none; }

/* -- MCQ question card -- */
.mcq-question { margin-bottom: var(--space-lg); }
.mcq-question .question-text {
  font-size: var(--text-base); line-height: 1.7; margin-bottom: var(--space-md);
}
.mcq-options {
  display: flex; flex-direction: column; gap: var(--space-sm);
  margin-bottom: var(--space-md);
}
.mcq-option {
  display: flex; align-items: flex-start; gap: var(--space-sm);
  padding: 10px 14px; border-radius: var(--glass-radius-sm);
  background: var(--glass-bg-light); border: var(--glass-border-subtle);
  cursor: pointer; transition: all var(--transition-fast);
}
.mcq-option:hover { background: var(--glass-bg); }
.mcq-option input[type="radio"] {
  margin-top: 3px; accent-color: var(--primary); flex-shrink: 0;
}
.mcq-option label { cursor: pointer; flex: 1; line-height: 1.5; }
.mcq-option.correct {
  background: rgba(34, 197, 94, 0.12); border-color: #22c55e;
}
.mcq-option.incorrect {
  background: rgba(239, 68, 68, 0.12); border-color: #ef4444;
}

/* -- MCQ feedback messages -- */
.mcq-feedback {
  display: none; padding: var(--space-md); border-radius: var(--glass-radius-sm);
  margin-top: var(--space-sm); font-size: var(--text-sm); line-height: 1.6;
}
.mcq-feedback.show { display: block; }
.mcq-feedback.correct-msg {
  background: rgba(34, 197, 94, 0.1); border: 1px solid #22c55e;
  color: #16a34a;
}
[data-theme="dark"] .mcq-feedback.correct-msg { color: #4ade80; }
.mcq-feedback.incorrect-msg {
  background: rgba(239, 68, 68, 0.1); border: 1px solid #ef4444;
  color: #dc2626;
}
[data-theme="dark"] .mcq-feedback.incorrect-msg { color: #f87171; }

/* -- MCQ action buttons -- */
.mcq-actions {
  display: flex; gap: var(--space-sm); margin-top: var(--space-sm);
}

/* -- FRQ practice block variant -- */
.practice-frq-block {
  border-left: 3px solid var(--secondary); margin-bottom: var(--space-lg);
}

/* -- Practice page back link -- */
.practice-back-link {
  display: inline-flex; align-items: center; gap: var(--space-xs);
  margin-top: var(--space-xl); font-size: var(--text-sm);
  color: var(--text-secondary);
}
.practice-back-link:hover { color: var(--text); }