:root {
  --bg-dark: #0f172a;
  --bg-card: rgba(30, 41, 59, 0.85);
  --primary: #3b82f6;
  --primary-hover: #2563eb;
  --secondary: #8b5cf6;
  --success: #10b981;
  --warning: #f59e0b;
  --danger: #ef4444;
  --text: #f8fafc;
  --text-main: #f8fafc;
  --text-muted: #94a3b8;
  --glass-border: rgba(255, 255, 255, 0.1);
}

.pics-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 16px;
  max-width: 320px;
  margin: 16px auto;
}

.pics-item {
  aspect-ratio: 1;
  background: rgba(255, 255, 255, 0.08);
  border: 2px solid rgba(255, 255, 255, 0.15);
  border-radius: 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 64px;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.25);
  transition: transform 0.2s ease, border-color 0.2s ease;
  user-select: none;
}

.pics-item:hover {
  transform: scale(1.05);
  border-color: var(--primary);
}

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

body {
  font-family: 'Outfit', sans-serif;
  background-color: var(--bg-dark);
  color: var(--text-main);
  background-image: radial-gradient(circle at top right, rgba(59, 130, 246, 0.15), transparent 40%),
                    radial-gradient(circle at bottom left, rgba(139, 92, 246, 0.15), transparent 40%);
  background-attachment: fixed;
  overflow-x: hidden;
  -webkit-tap-highlight-color: transparent;
}

.glass-card {
  background: var(--bg-card);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border: 1px solid var(--glass-border);
  border-radius: 16px;
  padding: 20px;
  box-shadow: 0 4px 20px rgba(0,0,0,0.2);
}

.mb-10 { margin-bottom: 10px; }
.mb-20 { margin-bottom: 20px; }
.mt-10 { margin-top: 10px; }
.mt-20 { margin-top: 20px; }
.w-100 { width: 100%; }
.text-center { text-align: center; }
.text-primary { color: var(--primary); }
.text-secondary { color: var(--secondary); }
.text-danger { color: var(--danger); }
.text-success { color: var(--success); }
.text-warning { color: var(--warning); }
.text-muted { color: var(--text-muted); }
.hidden { display: none !important; }
.flex-1 { flex: 1; }

/* Pulse Animation */
@keyframes pulse {
  0% { transform: scale(1); opacity: 1; }
  50% { transform: scale(1.05); opacity: 0.8; }
  100% { transform: scale(1); opacity: 1; }
}

.pulse {
  animation: pulse 2s ease-in-out infinite;
}

/* Button Variants */
.btn-danger { background: var(--danger); color: #fff; }
.btn-sm { padding: 8px 14px; font-size: 14px; border-radius: 8px; }

/* Game Icon Backgrounds */
.bg-puzzle { background: linear-gradient(135deg, #ec4899, #f43f5e); }
.bg-dance { background: linear-gradient(135deg, #f093fb, #f5576c); }
.bg-sing { background: linear-gradient(135deg, #4facfe, #00f2fe); }
.bg-group { background: linear-gradient(135deg, #43e97b, #38f9d7); }

/* Login Overlay */
.login-overlay {
  position: fixed;
  top: 0; left: 0; width: 100%; height: 100%;
  background: var(--bg-dark);
  background-image: radial-gradient(circle at top right, rgba(59, 130, 246, 0.2), transparent 40%),
                    radial-gradient(circle at bottom left, rgba(139, 92, 246, 0.2), transparent 40%);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 9999;
  padding: 20px;
}

/* Options Menu Overlay */
.options-overlay {
  position: fixed;
  top: 0; left: 0; width: 100%; height: 100%;
  background: rgba(0, 0, 0, 0.9);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 10000;
  padding: 20px;
}

.options-card {
  width: 100%;
  max-width: 500px;
  max-height: 90vh;
  overflow-y: auto;
  padding: 32px;
  margin: auto;
}

.options-section h3 {
  margin-bottom: 16px;
  font-size: 18px;
  color: var(--primary);
}

.option-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 12px 0;
  border-bottom: 1px solid var(--glass-border);
}

.option-row label {
  font-size: 16px;
}

.btn-toggle {
  padding: 8px 16px;
  border-radius: 8px;
  border: 1px solid var(--primary);
  background: var(--primary);
  color: white;
  font-size: 14px;
  cursor: pointer;
  transition: 0.2s;
}

.btn-toggle.off {
  background: rgba(255, 255, 255, 0.1);
  border-color: var(--text-muted);
  color: var(--text-muted);
}

/* Duolingo-style Top Navigation */
.top-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 64px;
  background: var(--bg-card);
  border-bottom: 1px solid var(--glass-border);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 24px;
  z-index: 1000;
  backdrop-filter: blur(20px);
}

.top-nav-left {
  display: flex;
  align-items: center;
}

.brand-small {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 24px;
  font-weight: 800;
  color: var(--primary);
}

.top-nav-center {
  display: flex;
  gap: 8px;
}

.nav-tab {
  padding: 12px 20px;
  border: none;
  background: transparent;
  color: var(--text-muted);
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  border-radius: 12px;
  display: flex;
  align-items: center;
  gap: 8px;
  transition: 0.2s;
}

.nav-tab:hover {
  color: var(--primary);
}

.nav-tab.active {
  background: var(--primary);
  color: white;
}

.top-nav-right {
  display: flex;
  align-items: center;
  gap: 16px;
}

.stats-counter {
  display: flex;
  align-items: center;
  gap: 6px;
  padding: 8px 12px;
  background: rgba(255, 255, 255, 0.05);
  border-radius: 20px;
  font-weight: 700;
  font-size: 16px;
}

.user-avatar-small {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: linear-gradient(135deg, #3b82f6, #8b5cf6);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 16px;
  cursor: pointer;
  transition: 0.2s;
}

.btn-icon {
  padding: 8px 12px;
  border: none;
  background: transparent;
  color: var(--text-muted);
  font-size: 20px;
  cursor: pointer;
  border-radius: 8px;
  transition: 0.2s;
}

.btn-icon:hover {
  background: rgba(255, 255, 255, 0.1);
  color: var(--primary);
}

/* Lesson Path (Duolingo-style) */
.lesson-path {
  padding-top: 80px;
  max-width: 800px;
  margin: 0 auto;
}

.path-header {
  text-align: center;
  margin-bottom: 40px;
}

.path-header h1 {
  font-size: 36px;
  font-weight: 800;
  color: var(--text-main);
}

.path-container {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 40px;
}

.lesson-node {
  display: flex;
  align-items: center;
  gap: 20px;
  width: 100%;
  max-width: 600px;
  padding: 20px;
  border-radius: 16px;
  transition: 0.3s;
}

.lesson-node.completed {
  background: rgba(34, 197, 94, 0.1);
  border: 2px solid rgba(34, 197, 94, 0.3);
}

.lesson-node.current {
  background: rgba(59, 130, 246, 0.1);
  border: 2px solid var(--primary);
}

.lesson-node.locked {
  background: rgba(255, 255, 255, 0.05);
  border: 2px solid var(--glass-border);
  opacity: 0.6;
}

.lesson-icon {
  width: 64px;
  height: 64px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 28px;
  flex-shrink: 0;
}

.lesson-node.completed .lesson-icon {
  background: linear-gradient(135deg, #22c55e, #16a34a);
  color: white;
}

.lesson-node.current .lesson-icon {
  background: linear-gradient(135deg, #3b82f6, #2563eb);
  color: white;
  animation: pulse 2s infinite;
}

.lesson-node.locked .lesson-icon {
  background: rgba(255, 255, 255, 0.1);
  color: var(--text-muted);
}

.lesson-info {
  flex: 1;
}

.lesson-info h3 {
  font-size: 18px;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 4px;
}

.lesson-info p {
  font-size: 14px;
  color: var(--text-muted);
}

.btn-lesson {
  padding: 12px 24px;
  border: none;
  border-radius: 12px;
  font-weight: 700;
  font-size: 14px;
  cursor: pointer;
  transition: 0.2s;
}

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

.btn-lesson.btn-start:hover {
  background: #2563eb;
}

.btn-lesson.btn-review {
  background: rgba(34, 197, 94, 0.2);
  color: #22c55e;
  border: 2px solid #22c55e;
}

.btn-lesson.btn-review:hover {
  background: rgba(34, 197, 94, 0.3);
}

.btn-lesson.btn-locked {
  background: rgba(255, 255, 255, 0.1);
  color: var(--text-muted);
  cursor: not-allowed;
}

/* Quick Access Panel */
.quick-access {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
  max-width: 800px;
  margin: 60px auto 40px;
  padding: 0 20px;
}

.quick-card {
  background: var(--bg-card);
  border: 1px solid var(--glass-border);
  border-radius: 16px;
  padding: 24px;
  text-align: center;
  cursor: pointer;
  transition: 0.3s;
}

.quick-card:hover {
  border-color: var(--primary);
  box-shadow: 0 8px 24px rgba(59, 130, 246, 0.2);
}

.quick-card i {
  font-size: 36px;
  margin-bottom: 12px;
}

.quick-card h3 {
  font-size: 18px;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 4px;
}

.quick-card p {
  font-size: 14px;
  color: var(--text-muted);
}

/* Content Area Adjustments for Top Nav */
.content-area {
  padding-top: 80px;
}

/* Shared Page Shortcuts Bar */
.page-shortcuts {
  margin-bottom: 24px;
  padding: 16px;
}

.page-shortcuts-header {
  margin-bottom: 12px;
}

.page-shortcuts-header h3 {
  font-size: 18px;
  font-weight: 700;
  color: var(--text-main);
  margin: 0 0 4px 0;
}

.page-shortcuts-header .subtitle {
  font-size: 14px;
  color: var(--text-muted);
  margin: 0;
}

.page-shortcuts-nav {
  display: flex;
  gap: 10px;
  flex-wrap: wrap;
}

.page-shortcut-btn {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 10px 16px;
  background: rgba(255, 255, 255, 0.05);
  border: 1px solid var(--glass-border);
  border-radius: 12px;
  color: var(--text-muted);
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: 0.2s;
}

.page-shortcut-btn:hover {
  background: rgba(59, 130, 246, 0.1);
  border-color: var(--primary);
  color: var(--primary);
}

.page-shortcut-btn.active {
  background: var(--primary);
  border-color: var(--primary);
  color: white;
}

.page-shortcut-btn i {
  font-size: 16px;
}

@media (max-width: 767px) {
  .page-shortcuts-nav {
    overflow-x: auto;
    flex-wrap: nowrap;
    padding-bottom: 8px;
  }

  .page-shortcut-btn {
    flex-shrink: 0;
    padding: 8px 12px;
    font-size: 13px;
  }

  .page-shortcut-btn i {
    font-size: 14px;
  }

  .page-shortcuts-header h3 {
    font-size: 16px;
  }
}

.login-card {
  width: 100%;
  max-width: 400px;
  padding: 40px 30px;
}

/* Layout Structure */
.app-wrapper {
  display: flex;
  height: 100vh;
  flex-direction: column;
}

.main-nav {
  display: flex;
  background: rgba(15, 23, 42, 0.95);
  border-top: 1px solid var(--glass-border);
  position: fixed;
  bottom: 0;
  width: 100%;
  z-index: 1000;
  padding-bottom: env(safe-area-inset-bottom);
}

.brand, .user-profile, .hide-mobile {
  display: none;
}

.nav-links {
  display: flex;
  width: 100%;
  justify-content: space-around;
  list-style: none;
}

.nav-item {
  padding: 16px 0;
  flex: 1;
  text-align: center;
  color: var(--text-muted);
  font-size: 24px;
  cursor: pointer;
  transition: 0.2s;
}

.nav-item a {
  color: var(--text-muted);
  text-decoration: none;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
}

.nav-item.active a,
.nav-item.active {
  color: var(--primary);
}

.nav-item:hover a {
  color: var(--primary);
}

.content-area {
  flex: 1;
  padding: 20px;
  padding-bottom: 80px; /* space for bottom nav */
  overflow-y: auto;
  position: relative;
}

/* Sidebar Toggle Button */
.sidebar-toggle {
  position: fixed;
  top: 20px;
  left: 20px;
  z-index: 1001;
  background: var(--bg-card);
  border: 1px solid var(--glass-border);
  border-radius: 12px;
  padding: 12px 16px;
  color: var(--text-main);
  font-size: 20px;
  cursor: pointer;
  display: none;
  transition: 0.3s;
}

.sidebar-toggle:hover {
  background: var(--primary);
  border-color: var(--primary);
}

/* Collapsed Sidebar State */
.main-nav.collapsed {
  transform: translateX(-100%);
  transition: transform 0.3s ease;
}

.content-area.expanded {
  padding-left: 20px !important;
}

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

/* Header (Mobile) */
.mobile-header {
  margin-bottom: 24px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--glass-border);
}

.mobile-profile {
  display: flex;
  align-items: center;
  gap: 12px;
}

.avatar {
  width: 48px;
  height: 48px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 800;
  font-size: 18px;
  overflow: hidden;
}

.avatar-large {
  width: 120px;
  height: 120px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 800;
  font-size: 40px;
  margin: 0 auto;
  overflow: hidden;
  transition: all 0.3s ease;
}

/* Custom Borders */
.border-solid { border: 4px solid var(--primary); }
.border-dashed { border: 4px dashed var(--secondary); }
.border-neon {
  border: 4px solid #fff;
  box-shadow: 0 0 10px #0ff, 0 0 20px #0ff, inset 0 0 10px #0ff;
}
.border-gold {
  border: 4px solid #ffd700;
  box-shadow: 0 4px 15px rgba(255, 215, 0, 0.4);
}

.border-options {
  flex-wrap: wrap;
}
.border-option {
  padding: 8px 16px;
  background: rgba(255,255,255,0.05);
  border: 1px solid var(--glass-border);
  border-radius: 20px;
  cursor: pointer;
  transition: 0.2s;
  font-size: 14px;
}
.border-option:hover { background: rgba(255,255,255,0.1); }
.border-option.active {
  background: var(--primary);
  border-color: var(--primary);
  color: #fff;
}

/* Typography */
h1 { font-size: 28px; margin-bottom: 8px; font-weight: 800; }
.subtitle { color: var(--text-muted); font-size: 16px; margin-bottom: 24px; }
h3 { font-size: 18px; margin-bottom: 8px; }

/* Buttons & Inputs */
.btn {
  padding: 14px 20px;
  border-radius: 12px;
  border: none;
  font-family: inherit;
  font-weight: 600;
  font-size: 16px;
  cursor: pointer;
  transition: 0.2s;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
}
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:active { background: var(--primary-hover); }
.btn-success { background: var(--success); color: #fff; }
.btn-secondary { background: rgba(255,255,255,0.1); color: #fff; }

.form-control {
  width: 100%;
  padding: 14px;
  border-radius: 10px;
  background: rgba(0,0,0,0.3);
  border: 1px solid var(--glass-border);
  color: #fff;
  font-family: inherit;
  font-size: 16px;
}
.form-control:focus { outline: none; border-color: var(--primary); }

/* Dashboard Grid */
.stats-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 16px;
}
.stat {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  padding: 24px 16px;
}
.stat i { font-size: 32px; margin-bottom: 12px; }

/* Students List */
.student-list {
  display: grid;
  gap: 12px;
}
.student-card {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px;
  background: rgba(255,255,255,0.03);
  border-radius: 12px;
  border: 1px solid var(--glass-border);
}
.student-card-info {
  display: flex;
  align-items: center;
  gap: 12px;
}
.student-card .avatar { width: 40px; height: 40px; font-size: 14px; }
.btn-remove { background: rgba(239, 68, 68, 0.2); color: var(--danger); padding: 8px 12px; border-radius: 8px; border:none; cursor:pointer;}

/* Assessment */
.diff-selector {
  display: flex;
  gap: 8px;
}
.btn-diff {
  flex: 1;
  background: rgba(255,255,255,0.05);
  color: var(--text-muted);
  border: 1px solid var(--glass-border);
}
.btn-diff.active[data-diff="Easy"] { background: rgba(16, 185, 129, 0.2); border-color: var(--success); color: var(--success); }
.btn-diff.active[data-diff="Medium"] { background: rgba(245, 158, 11, 0.2); border-color: var(--warning); color: var(--warning); }
.btn-diff.active[data-diff="Hard"] { background: rgba(239, 68, 68, 0.2); border-color: var(--danger); color: var(--danger); }

/* Flash Screen */
.flash-screen {
  position: absolute;
  top: 0; left: 0; width: 100%; height: 100%;
  background: var(--bg-dark);
  z-index: 500;
  padding: 20px;
  display: flex;
  flex-direction: column;
}
.flash-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
  font-size: 18px;
  font-weight: 600;
}
.badge { padding: 4px 12px; border-radius: 20px; font-size: 14px; }
.bg-success { background: rgba(16, 185, 129, 0.2); color: var(--success); border: 1px solid var(--success); }
.bg-warning { background: rgba(245, 158, 11, 0.2); color: var(--warning); border: 1px solid var(--warning); }
.bg-danger { background: rgba(239, 68, 68, 0.2); color: var(--danger); border: 1px solid var(--danger); }
.flash-question {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.2), rgba(139, 92, 246, 0.2));
  border: 2px solid rgba(59, 130, 246, 0.5);
}
.flash-question h2 { font-size: 32px; line-height: 1.4; }
.score-buttons { display: flex; gap: 12px; margin-top: 16px; }
.score-buttons .btn { flex: 1; padding: 20px; font-size: 18px; flex-direction: column; }
.score-correct { background: rgba(16, 185, 129, 0.2); color: var(--success); border: 2px solid var(--success); }
.score-incorrect { background: rgba(239, 68, 68, 0.2); color: var(--danger); border: 2px solid var(--danger); }

/* Multimedia Cards */
.media-grid { display: grid; gap: 16px; }
.media-card { text-align: center; }
.media-icon {
  width: 64px; height: 64px; margin: 0 auto 16px;
  border-radius: 16px; display: flex; align-items: center; justify-content: center;
  font-size: 32px; color: #fff;
}
.bg-plant { background: linear-gradient(135deg, #10b981, #047857); }
.bg-machine { background: linear-gradient(135deg, #f59e0b, #b45309); }
.bg-weather { background: linear-gradient(135deg, #3b82f6, #1d4ed8); }

/* Records Table */
.table-responsive { overflow-x: auto; }
.records-table { width: 100%; border-collapse: collapse; min-width: 400px; }
.records-table th, .records-table td {
  padding: 12px;
  text-align: left;
  border-bottom: 1px solid var(--glass-border);
}
.records-table th { color: var(--text-muted); font-size: 14px; }
.records-table tr:last-child td { border-bottom: none; }

/* Mobile-Specific Layout */
@media (max-width: 767px) {
  .content-area {
    padding: 16px;
    padding-bottom: 100px;
  }

  .options-card {
    max-width: 100%;
    padding: 20px;
  }

  .options-overlay {
    padding: 10px;
  }

  /* Top Navigation Mobile */
  .top-nav {
    padding: 0 16px;
    height: 56px;
  }

  .brand-small span {
    display: none;
  }

  .top-nav-center {
    gap: 4px;
  }

  .nav-tab span {
    display: none;
  }

  .nav-tab {
    padding: 8px 12px;
  }

  .stats-counter {
    padding: 6px 10px;
    font-size: 14px;
  }

  .stats-counter span {
    display: none;
  }

  .user-avatar-small {
    width: 36px;
    height: 36px;
    font-size: 14px;
  }

  .btn-icon {
    padding: 8px;
    font-size: 18px;
  }

  /* Lesson Path Mobile */
  .lesson-path {
    padding-top: 70px;
    padding: 70px 16px 0;
  }

  .path-header h1 {
    font-size: 28px;
  }

  .lesson-node {
    padding: 16px;
    gap: 12px;
  }

  .lesson-icon {
    width: 48px;
    height: 48px;
    font-size: 20px;
  }

  .lesson-info h3 {
    font-size: 16px;
  }

  .lesson-info p {
    font-size: 12px;
  }

  .btn-lesson {
    padding: 8px 16px;
    font-size: 12px;
  }

  /* Quick Access Mobile */
  .quick-access {
    grid-template-columns: 1fr;
    gap: 12px;
    padding: 0 16px;
  }

  .quick-card {
    padding: 16px;
  }

  .quick-card i {
    font-size: 28px;
  }
  
  /* Scrollable Bottom Nav for Mobile */
  .main-nav {
    padding: 8px 10px;
    padding-bottom: calc(8px + env(safe-area-inset-bottom));
  }
  .nav-links {
    justify-content: flex-start;
    overflow-x: auto;
    scroll-snap-type: x mandatory;
    -webkit-overflow-scrolling: touch;
    gap: 8px;
  }
  .nav-links::-webkit-scrollbar {
    display: none;
  }
  .nav-item {
    flex: 0 0 auto;
    min-width: 64px;
    padding: 12px 8px;
    border-radius: 16px;
    scroll-snap-align: center;
    font-size: 22px;
  }
  .nav-item.active {
    background: rgba(59, 130, 246, 0.2);
    transform: translateY(0);
  }
  
  /* Stacked Grids for Mobile */
  .stats-grid {
    grid-template-columns: 1fr;
    gap: 12px;
  }
  
  /* Forms & Filters */
  .filter-bar {
    flex-direction: column;
    gap: 10px;
  }
  .filter-bar select, .filter-bar button {
    width: 100%;
  }
  
  /* Score Buttons */
  .score-buttons {
    flex-direction: column;
  }
  
  /* Card spacing */
  .glass-card {
    padding: 16px;
  }
  
  /* Flash Screen Mobile */
  .flash-question h2 {
    font-size: 24px;
  }
  
  /* OYO Mobile Easter Egg Adjustment */
  .easter-egg p {
    font-size: 16px;
  }
}

/* Desktop/Laptop Overrides */
@media (min-width: 768px) {
  .app-wrapper { flex-direction: row; }
  .hide-desktop { display: none; }
  .hide-mobile { display: inline-block; }

  .sidebar-toggle {
    display: block;
  }

  .options-card {
    max-width: 450px;
    padding: 28px;
  }

  .main-nav {
    position: fixed;
    left: 0;
    top: 0;
    height: 100vh;
    width: 280px;
    flex-direction: column;
    padding: 32px 20px;
    border-top: none;
    border-right: 1px solid var(--glass-border);
    background: rgba(15, 23, 42, 0.95);
    backdrop-filter: blur(20px);
    z-index: 1000;
    overflow-y: auto;
    overflow-x: hidden;
    transition: transform 0.3s ease;
    scrollbar-width: none; /* Firefox */
    -ms-overflow-style: none; /* IE/Edge */
  }

  .main-nav::-webkit-scrollbar {
    display: none; /* Chrome/Safari */
  }

  .brand {
    display: flex;
    align-items: center;
    gap: 12px;
    font-size: 24px;
    color: var(--primary);
    margin-bottom: 32px;
  }

  .user-profile {
    display: flex;
    align-items: center;
    gap: 16px;
    padding: 16px;
    background: rgba(255,255,255,0.05);
    border-radius: 16px;
    margin-bottom: 32px;
  }
  .user-info span { color: var(--text-muted); font-size: 14px; }

  .nav-links {
    flex-direction: column;
    gap: 6px;
    justify-content: flex-start;
  }

  .nav-item {
    text-align: left;
    padding: 14px 20px;
    font-size: 16px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    gap: 16px;
  }
  .nav-item.active { background: rgba(59, 130, 246, 0.1); }

  .content-area {
    padding-left: 300px;
    padding-bottom: 20px;
  }

  .content-area { padding: 40px; padding-bottom: 40px; }

  .stats-grid, .media-grid { grid-template-columns: repeat(3, 1fr); }

  .flash-screen { padding: 60px; }
  .score-buttons { flex-direction: row; }
}

/* Large Desktop / High DPI (1920x1080 @ 125% scaling) */
@media (min-width: 1400px) {
  .main-nav {
    width: 320px;
    padding: 32px 24px;
    scrollbar-width: none;
    -ms-overflow-style: none;
  }

  .main-nav::-webkit-scrollbar {
    display: none;
  }

  .brand {
    font-size: 28px;
    margin-bottom: 32px;
  }

  .user-profile {
    margin-bottom: 32px;
  }

  .nav-item {
    padding: 16px 28px;
    font-size: 18px;
  }

  .content-area {
    padding-left: 340px;
    padding: 50px;
    padding-bottom: 50px;
  }

  .stats-grid, .media-grid {
    grid-template-columns: repeat(4, 1fr);
    gap: 24px;
  }

  .glass-card {
    padding: 28px;
  }

  h1 { font-size: 36px; }
  h2 { font-size: 28px; }
  h3 { font-size: 22px; }

  .btn {
    padding: 16px 24px;
    font-size: 18px;
  }

  .form-control {
    padding: 16px;
    font-size: 16px;
  }
}

/* Animations & Easter Eggs */
@keyframes shine { 
  0% { background-position: -200% center; } 
  100% { background-position: 200% center; } 
}

.easter-egg {
  cursor: pointer;
  transition: box-shadow 0.3s ease;
}
.easter-egg:hover {
  box-shadow: 0 10px 30px rgba(229, 46, 113, 0.4);
}

.easter-egg p {
  background: linear-gradient(90deg, #ff8a00, #e52e71, #ff8a00);
  background-size: 200% auto;
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  font-weight: 800;
  font-size: 18px;
  letter-spacing: 1px;
  animation: shine 3s linear infinite;
}

/* Enhancing Interactive Elements */
.glass-card {
  transition: box-shadow 0.3s ease;
}
.glass-card:not(.login-card):not(#assessment-flash .glass-card):hover {
  box-shadow: 0 12px 30px rgba(0,0,0,0.4), 0 0 15px rgba(59, 130, 246, 0.2);
}

.btn {
  position: relative;
  overflow: hidden;
}
.btn::after {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  width: 5px;
  height: 5px;
  background: rgba(255, 255, 255, 0.5);
  opacity: 0;
  border-radius: 100%;
  transform: scale(1, 1) translate(-50%);
  transform-origin: 50% 50%;
}
.btn:active::after {
  animation: ripple 0.6s ease-out;
}
@keyframes ripple {
  0% { transform: scale(0, 0); opacity: 0.5; }
  100% { transform: scale(40, 40); opacity: 0; }
}
.btn:hover {
  filter: brightness(1.1);
}

/* Games Section */
.game-screen {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: var(--bg-dark);
  z-index: 1000;
  padding: 20px;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
}

.game-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
}

.game-content {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 400px;
  font-size: 24px;
  text-align: center;
  background: linear-gradient(135deg, rgba(59, 130, 246, 0.2), rgba(139, 92, 246, 0.2));
  border: 2px solid rgba(59, 130, 246, 0.5);
}

.game-controls {
  max-width: 600px;
  margin: 0 auto;
}

/* Scoreboard Section */
.scoreboard-header {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.fairness-banner {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 16px;
  background: rgba(245, 158, 11, 0.2);
  border: 2px solid var(--warning);
  border-radius: 12px;
  animation: pulse 2s infinite;
}

.fairness-banner i {
  font-size: 24px;
}

.scoreboard-table {
  overflow: hidden;
}

.scoreboard-table .records-table th,
.scoreboard-table .records-table td {
  padding: 16px;
  font-size: 18px;
}

.scoreboard-table .records-table th {
  background: rgba(59, 130, 246, 0.2);
  color: var(--primary);
  font-weight: 700;
}

.scoreboard-table tr.highlight-zero {
  background: rgba(245, 158, 11, 0.15);
}

.scoreboard-table tr.highlight-zero td {
  color: var(--warning);
}

.scoreboard-table .rank-1 {
  background: rgba(255, 215, 0, 0.15);
}

.scoreboard-table .rank-1 td:first-child {
  color: #ffd700;
  font-weight: 800;
}

/* Fullscreen TV Mode */
.fullscreen-tv {
  position: fixed !important;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  z-index: 9999;
  background: var(--bg-dark);
  padding: 20px;
  overflow-y: auto;
}

.fullscreen-tv .scoreboard-header button,
.fullscreen-tv .scoreboard-header select {
  font-size: 18px;
  padding: 16px 20px;
}

.fullscreen-tv .records-table th,
.fullscreen-tv .records-table td {
  font-size: 24px;
  padding: 20px;
}

.fullscreen-tv h1 {
  font-size: 48px;
}

.fullscreen-tv .subtitle {
  font-size: 24px;
}

/* Game Content Templates */
.dance-animation {
  font-size: 48px;
  animation: bounce 1s infinite;
}

.sing-lyrics {
  font-size: 32px;
  line-height: 1.8;
}

.sing-lyrics .highlight-term {
  color: var(--primary);
  font-weight: 800;
  text-shadow: 0 0 10px var(--primary);
}

.groupings-timer {
  font-size: 72px;
  font-weight: 800;
  color: var(--primary);
  margin: 20px 0;
}

.groupings-instruction {
  font-size: 28px;
  line-height: 1.6;
}

@keyframes bounce {
  0%, 100% { transform: translateY(0); }
  50% { transform: translateY(-20px); }
}

/* Lessons Section */
.lesson-screen {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: var(--bg-dark);
  z-index: 1000;
  padding: 20px;
  display: flex;
  flex-direction: column;
  overflow-y: auto;
}

.lesson-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
}

.lesson-content {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 400px;
  font-size: 28px;
  text-align: center;
  background: linear-gradient(135deg, rgba(16, 185, 129, 0.2), rgba(59, 130, 246, 0.2));
  border: 2px solid rgba(16, 185, 129, 0.5);
  padding: 40px;
}

.lesson-content h3 {
  font-size: 36px;
  margin-bottom: 20px;
}

.lesson-content p {
  font-size: 24px;
  line-height: 1.6;
  max-width: 800px;
}

.lesson-controls {
  display: flex;
  align-items: center;
  justify-content: center;
  max-width: 600px;
  margin: 20px auto;
  padding: 16px;
}

.lesson-fullscreen {
  position: fixed !important;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  z-index: 9999;
  background: var(--bg-dark);
  padding: 40px;
  overflow-y: auto;
}

.lesson-fullscreen .lesson-content {
  font-size: 48px;
}

.lesson-fullscreen .lesson-content h3 {
  font-size: 64px;
}

.lesson-fullscreen .lesson-content p {
  font-size: 42px;
}

/* Game Fullscreen Mode */
.game-fullscreen {
  position: fixed !important;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  z-index: 9999;
  background: var(--bg-dark);
  padding: 40px;
  overflow-y: auto;
}

.game-fullscreen .game-content {
  font-size: 48px;
  min-height: 60vh;
}

.game-fullscreen .game-content h3 {
  font-size: 64px;
}

.game-fullscreen .game-content p {
  font-size: 42px;
}

.game-fullscreen .game-controls {
  font-size: 24px;
}

/* Light/Dark Mode */
[data-theme="light"] {
  --bg-dark: #f8fafc;
  --bg-card: rgba(255, 255, 255, 0.95);
  --text: #1e293b;
  --text-main: #1e293b;
  --text-muted: #64748b;
  --glass-border: rgba(0, 0, 0, 0.1);
}

[data-theme="light"] body {
  background-color: var(--bg-dark);
  background-image: radial-gradient(circle at top right, rgba(59, 130, 246, 0.1), transparent 40%),
                    radial-gradient(circle at bottom left, rgba(139, 92, 246, 0.1), transparent 40%);
}

[data-theme="light"] .glass-card {
  background: var(--bg-card);
  border: 1px solid var(--glass-border);
}

[data-theme="light"] .main-nav {
  background: rgba(255, 255, 255, 0.95);
  border-top: 1px solid var(--glass-border);
}

[data-theme="light"] .form-control {
  background: rgba(255, 255, 255, 0.8);
  border: 1px solid var(--glass-border);
  color: var(--text-main);
}

[data-theme="light"] .form-control:focus {
  border-color: var(--primary);
}

[data-theme="light"] .student-card,
[data-theme="light"] .media-card {
  background: rgba(255, 255, 255, 0.7);
}

[data-theme="light"] .login-overlay {
  background: var(--bg-dark);
  background-image: radial-gradient(circle at top right, rgba(59, 130, 246, 0.1), transparent 40%),
                    radial-gradient(circle at bottom left, rgba(139, 92, 246, 0.1), transparent 40%);
}

[data-theme="light"] .top-nav {
  background: rgba(255, 255, 255, 0.95);
  border-bottom-color: var(--glass-border);
}

[data-theme="light"] .nav-tab {
  color: var(--text-muted);
}

[data-theme="light"] .nav-tab.active {
  background: var(--primary);
  color: white;
}

[data-theme="light"] .btn-secondary {
  background: rgba(0, 0, 0, 0.05);
  color: var(--text-main);
}

[data-theme="light"] .flash-screen,
[data-theme="light"] .lesson-screen,
[data-theme="light"] .game-screen {
  background: var(--bg-dark);
}

[data-theme="light"] .options-overlay {
  background: rgba(0, 0, 0, 0.6);
}
/* Performance Mode - Optimizations for Low-End Hardware */
.performance-mode {
  background-image: none !important;
  background-color: #0f172a !important;
}

.performance-mode * {
  box-shadow: none !important;
  transition: none !important;
  animation: none !important;
}

.performance-mode .glass-card,
.performance-mode .top-nav,
.performance-mode .main-nav,
.performance-mode .video-modal-content,
.performance-mode .options-card,
.performance-mode .flash-screen {
  backdrop-filter: none !important;
  -webkit-backdrop-filter: none !important;
  background: #1e293b !important;
  border-color: #334155 !important;
}

.performance-mode .pulse {
  animation: none !important;
}

.performance-mode .animate-in {
  animation: none !important;
  opacity: 1 !important;
  transform: none !important;
}

.performance-mode .bg-plant,
.performance-mode .bg-machine,
.performance-mode .bg-weather,
.performance-mode .bg-pdf,
.performance-mode .bg-ppt {
  background: #334155 !important;
}

/* DepEd K-12 Proficiency Level Badges */
.deped-outstanding { background: linear-gradient(135deg, #10b981, #059669); color: white; font-weight: 700; }
.deped-very-satisfactory { background: linear-gradient(135deg, #3b82f6, #2563eb); color: white; font-weight: 700; }
.deped-satisfactory { background: linear-gradient(135deg, #8b5cf6, #7c3aed); color: white; font-weight: 700; }
.deped-fairly-satisfactory { background: linear-gradient(135deg, #f59e0b, #d97706); color: white; font-weight: 700; }
.deped-dnme { background: linear-gradient(135deg, #ef4444, #dc2626); color: white; font-weight: 700; }

/* Fullscreen Assessment Mode (Student Test-Taking) */
.assessment-fullscreen {
  position: fixed !important;
  top: 0;
  left: 0;
  width: 100vw;
  height: 100vh;
  z-index: 99998;
  background: var(--bg-dark);
  padding: 40px;
  overflow-y: auto;
  display: flex;
  flex-direction: column;
}

.assessment-fullscreen .flash-header {
  font-size: 28px;
  padding: 20px 0;
}

.assessment-fullscreen .flash-question h2 {
  font-size: 42px;
  line-height: 1.4;
}

.assessment-fullscreen .score-btn {
  font-size: 32px;
  padding: 20px 32px;
  min-width: 80px;
}

.assessment-fullscreen .rubric-labels {
  font-size: 18px !important;
}

.assessment-fullscreen .score-incorrect {
  font-size: 24px;
  padding: 16px 32px;
}

/* File Manager Styles */
.file-list-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 12px 16px;
  background: rgba(255,255,255,0.03);
  border-radius: 10px;
  margin-bottom: 8px;
  border: 1px solid rgba(255,255,255,0.05);
  transition: all 0.2s ease;
}

.file-list-item:hover {
  background: rgba(59, 130, 246, 0.1);
  border-color: var(--primary);
}

.file-icon { font-size: 24px; margin-right: 12px; }
.file-icon.pdf { color: #ef4444; }
.file-icon.doc { color: #3b82f6; }
.file-icon.ppt { color: #f59e0b; }
.file-icon.img { color: #10b981; }
.file-icon.vid { color: #8b5cf6; }
.file-icon.csv { color: #06b6d4; }
.file-icon.json { color: #f97316; }

/* Export Modal */
.export-modal {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background: rgba(0,0,0,0.85);
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 99999;
}

.export-modal-content {
  width: 90%;
  max-width: 550px;
  padding: 32px;
  border-radius: 20px;
}

/* Hamburger Menu (replaces inline More Teacher Tools) */
.hamburger-btn {
  font-size: 20px;
  margin-right: 8px;
  color: var(--text-muted);
  transition: color 0.2s;
}
.hamburger-btn:hover { color: var(--primary); }

.hamburger-panel {
  position: fixed;
  top: 0;
  left: 0;
  width: 280px;
  height: 100vh;
  background: var(--bg-dark, #0f172a);
  border-right: 1px solid rgba(255,255,255,0.08);
  z-index: 99990;
  display: flex;
  flex-direction: column;
  box-shadow: 8px 0 40px rgba(0,0,0,0.5);
  transform: translateX(0);
  transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1), opacity 0.3s;
  opacity: 1;
}

.hamburger-panel.hidden {
  transform: translateX(-100%);
  opacity: 0;
  pointer-events: none;
}

.hamburger-panel-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 20px 20px 16px;
  border-bottom: 1px solid rgba(255,255,255,0.06);
}

.hamburger-panel-header h3 {
  font-size: 18px;
  font-weight: 700;
  color: var(--text-color);
  display: flex;
  align-items: center;
  gap: 10px;
}

.hamburger-panel-nav {
  flex: 1;
  overflow-y: auto;
  padding: 12px;
}

.hamburger-item {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 14px 16px;
  border-radius: 12px;
  color: var(--text-muted);
  text-decoration: none;
  font-size: 15px;
  font-weight: 500;
  transition: all 0.2s ease;
  margin-bottom: 4px;
}

.hamburger-item:hover {
  background: rgba(59, 130, 246, 0.12);
  color: var(--primary);
}

.hamburger-item.active {
  background: rgba(59, 130, 246, 0.18);
  color: var(--primary);
  font-weight: 700;
}

.hamburger-item i {
  font-size: 18px;
  width: 24px;
  text-align: center;
}

/* Hide old page-shortcuts when hamburger is active */
.page-shortcuts {
  display: none !important;
}

/* Light mode hamburger */
body.light-mode .hamburger-panel {
  background: #f1f5f9;
  border-right-color: rgba(0,0,0,0.08);
  box-shadow: 8px 0 40px rgba(0,0,0,0.1);
}
body.light-mode .hamburger-item { color: #475569; }
body.light-mode .hamburger-item:hover { background: rgba(59,130,246,0.08); color: #2563eb; }
body.light-mode .hamburger-item.active { background: rgba(59,130,246,0.12); color: #2563eb; }

/* ========================================
   COMPREHENSIVE MOBILE OPTIMIZATION
   Mobile-First Responsive Design
   ======================================== */

/* Base Mobile Optimizations (320px - 479px) */
@media (max-width: 479px) {
  /* Root sizing */
  :root {
    font-size: 14px;
  }

  body {
    font-size: 14px;
    line-height: 1.5;
  }

  /* Typography - Smaller on tiny screens */
  h1 { font-size: 22px; margin-bottom: 12px; }
  h2 { font-size: 20px; margin-bottom: 10px; }
  h3 { font-size: 16px; margin-bottom: 8px; }
  h4 { font-size: 14px; margin-bottom: 6px; }
  
  .subtitle { font-size: 13px; margin-bottom: 16px; }
  p { font-size: 13px; line-height: 1.5; }

  /* Spacing adjustments */
  .glass-card { padding: 12px; margin-bottom: 8px; }
  .mb-10 { margin-bottom: 8px; }
  .mb-20 { margin-bottom: 12px; }
  .mt-10 { margin-top: 8px; }
  .mt-20 { margin-top: 12px; }

  /* Top navigation improvements */
  .top-nav {
    height: 52px;
    padding: 0 12px;
  }

  .brand-small {
    font-size: 18px;
    gap: 8px;
  }

  .brand-small i {
    font-size: 20px;
  }

  .nav-tab {
    padding: 6px 10px;
    font-size: 12px;
    gap: 4px;
    border-radius: 8px;
  }

  .nav-tab i {
    font-size: 16px;
  }

  .top-nav-right {
    gap: 8px;
  }

  .user-avatar-small {
    width: 32px;
    height: 32px;
    font-size: 12px;
  }

  .btn-icon {
    padding: 6px;
    font-size: 16px;
  }

  .stats-counter {
    padding: 4px 8px;
    font-size: 12px;
    gap: 4px;
  }

  /* Button sizing - touch-friendly minimum 40px */
  .btn {
    padding: 10px 16px;
    font-size: 13px;
    border-radius: 8px;
    min-height: 40px;
    gap: 6px;
  }

  .btn-sm {
    padding: 8px 12px;
    font-size: 12px;
    min-height: 36px;
  }

  /* Forms - better mobile sizing */
  .form-control {
    padding: 12px;
    font-size: 16px; /* Prevents zoom on iOS */
    border-radius: 8px;
    margin-bottom: 12px;
  }

  .form-group {
    margin-bottom: 16px;
  }

  label {
    font-size: 13px;
    margin-bottom: 6px;
    display: block;
  }

  /* Login card adjustments */
  .login-card {
    max-width: 100%;
    padding: 24px 16px;
    border-radius: 12px;
  }

  .login-card h2 {
    font-size: 24px;
  }

  .login-card h3 {
    font-size: 14px;
  }

  /* Options menu mobile */
  .options-card {
    max-width: 100%;
    padding: 16px;
    max-height: 85vh;
  }

  .options-section h3 {
    font-size: 14px;
    margin-bottom: 12px;
  }

  .option-row {
    padding: 10px 0;
  }

  .option-row label {
    font-size: 13px;
  }

  .btn-toggle {
    padding: 6px 12px;
    font-size: 12px;
  }

  /* Grid adjustments */
  .stats-grid {
    grid-template-columns: 1fr;
    gap: 10px;
  }

  .stat {
    padding: 16px 12px;
  }

  .stat i {
    font-size: 24px;
  }

  .stat h3, .stat p {
    font-size: 12px;
  }

  .media-grid {
    grid-template-columns: 1fr;
    gap: 10px;
  }

  .media-card {
    padding: 12px;
  }

  .media-icon {
    width: 48px;
    height: 48px;
    font-size: 24px;
    margin: 0 auto 10px;
  }

  .media-card h3 {
    font-size: 14px;
  }

  .media-card p {
    font-size: 12px;
  }

  /* Lesson nodes mobile */
  .lesson-node {
    padding: 12px;
    gap: 12px;
    margin-bottom: 12px;
  }

  .lesson-icon {
    width: 40px;
    height: 40px;
    font-size: 18px;
    flex-shrink: 0;
  }

  .lesson-info h3 {
    font-size: 14px;
  }

  .lesson-info p {
    font-size: 11px;
  }

  .btn-lesson {
    padding: 6px 12px;
    font-size: 11px;
  }

  /* Quick access on mobile */
  .quick-access {
    grid-template-columns: 1fr;
    gap: 10px;
    margin: 40px 16px;
    padding: 0;
  }

  .quick-card {
    padding: 16px;
  }

  .quick-card i {
    font-size: 28px;
  }

  .quick-card h3 {
    font-size: 14px;
  }

  .quick-card p {
    font-size: 11px;
  }

  /* Content area mobile */
  .content-area {
    padding: 12px;
    padding-top: 70px;
    padding-bottom: 90px;
  }

  /* Lesson path mobile */
  .lesson-path {
    padding-top: 70px;
    padding-left: 8px;
    padding-right: 8px;
  }

  .path-header {
    margin-bottom: 24px;
  }

  .path-header h1 {
    font-size: 22px;
  }

  /* Modal adjustments */
  .login-overlay {
    padding: 12px;
  }

  .options-overlay {
    padding: 12px;
  }

  /* Game/Lesson screens */
  .game-screen,
  .lesson-screen {
    padding: 12px;
  }

  .game-header,
  .lesson-header {
    margin-bottom: 12px;
    flex-direction: column;
    gap: 10px;
  }

  .game-header h2,
  .lesson-header h2 {
    font-size: 18px;
  }

  .game-content,
  .lesson-content {
    min-height: 300px;
    font-size: 18px;
    padding: 20px;
  }

  .lesson-content h3 {
    font-size: 24px;
    margin-bottom: 12px;
  }

  .lesson-content p {
    font-size: 16px;
  }

  /* Score buttons mobile */
  .score-buttons {
    flex-direction: column;
    gap: 8px;
  }

  .score-buttons .btn {
    padding: 12px;
    font-size: 12px;
  }

  /* Tables mobile */
  .records-table {
    font-size: 12px;
  }

  .records-table th,
  .records-table td {
    padding: 8px;
  }

  /* Filter bar mobile */
  .filter-bar {
    flex-direction: column;
    gap: 8px;
  }

  .filter-bar button,
  .filter-bar select {
    width: 100%;
    padding: 10px;
    font-size: 14px;
  }

  /* Avatar sizing */
  .avatar {
    width: 40px;
    height: 40px;
    font-size: 14px;
  }

  .avatar-large {
    width: 100px;
    height: 100px;
    font-size: 36px;
    margin: 12px auto;
  }

  /* Student cards mobile */
  .student-card {
    padding: 12px;
    flex-wrap: wrap;
  }

  .student-card-info {
    gap: 10px;
    flex: 1;
  }

  .btn-remove {
    padding: 6px 10px;
    font-size: 12px;
  }

  /* Assessment difficulty selector */
  .diff-selector {
    gap: 6px;
  }

  .btn-diff {
    padding: 8px 12px;
    font-size: 12px;
  }

  /* Select dropdowns */
  select {
    width: 100%;
    padding: 10px;
    font-size: 14px;
    border-radius: 8px;
    margin-bottom: 12px;
  }

  /* Checkboxes & Radios - larger touch targets */
  input[type="checkbox"],
  input[type="radio"] {
    width: 18px;
    height: 18px;
    cursor: pointer;
  }

  /* Prevent zoom on input focus in iOS */
  input[type="text"],
  input[type="email"],
  input[type="password"],
  input[type="number"],
  textarea,
  select {
    font-size: 16px;
  }

  /* Better spacing around interactive elements */
  button,
  a[role="button"],
  input[type="button"],
  input[type="submit"] {
    min-height: 44px;
    min-width: 44px;
  }

  /* Touch feedback */
  button:active,
  a:active {
    opacity: 0.8;
  }

  /* Reduce animations on mobile for performance */
  @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;
    }
  }

  /* Safe area support for notched phones */
  .top-nav {
    padding-left: max(12px, env(safe-area-inset-left));
    padding-right: max(12px, env(safe-area-inset-right));
    padding-top: env(safe-area-inset-top);
  }

  .content-area {
    padding-left: max(12px, env(safe-area-inset-left));
    padding-right: max(12px, env(safe-area-inset-right));
  }

  /* Bottom safe area for home indicator */
  body {
    padding-bottom: env(safe-area-inset-bottom);
  }

  .main-nav {
    padding-bottom: calc(8px + env(safe-area-inset-bottom));
  }
}

/* Small phones/tablets (480px - 767px) */
@media (min-width: 480px) and (max-width: 767px) {
  :root {
    font-size: 15px;
  }

  h1 { font-size: 26px; }
  h2 { font-size: 22px; }
  h3 { font-size: 18px; }
  
  .subtitle { font-size: 14px; }

  .glass-card { padding: 16px; }

  .top-nav {
    height: 56px;
    padding: 0 16px;
  }

  .brand-small {
    font-size: 20px;
    gap: 10px;
  }

  .nav-tab {
    padding: 8px 14px;
    font-size: 13px;
  }

  .btn {
    padding: 12px 18px;
    font-size: 14px;
    min-height: 44px;
  }

  .form-control {
    padding: 12px;
    font-size: 16px;
  }

  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 12px;
  }

  .media-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 12px;
  }

  .quick-access {
    grid-template-columns: repeat(2, 1fr);
    gap: 12px;
  }

  .content-area {
    padding: 16px;
    padding-top: 80px;
    padding-bottom: 100px;
  }

  /* Safe areas for small devices */
  .top-nav {
    padding-left: max(16px, env(safe-area-inset-left));
    padding-right: max(16px, env(safe-area-inset-right));
  }
}

/* Landscape mode optimizations */
@media (max-height: 500px) {
  .top-nav {
    height: 48px;
    padding: 0 12px;
  }

  .content-area {
    padding-top: 60px;
    padding-bottom: 60px;
  }

  h1 { font-size: 18px; margin-bottom: 8px; }
  h2 { font-size: 16px; margin-bottom: 6px; }
  h3 { font-size: 14px; margin-bottom: 4px; }

  .glass-card { padding: 12px; margin-bottom: 8px; }

  .btn { padding: 8px 14px; font-size: 12px; }
}

/* Tablet & Medium screens (768px - 1024px) */
@media (min-width: 768px) and (max-width: 1024px) {
  .stats-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .media-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .quick-access {
    grid-template-columns: repeat(2, 1fr);
  }

  .content-area {
    padding: 28px;
  }
}

/* Touch-friendly improvements for all mobile */
@media (hover: none) and (pointer: coarse) {
  /* Increase touch targets */
  button,
  a[role="button"],
  input[type="button"],
  input[type="submit"],
  .nav-item,
  .nav-tab,
  .quick-card,
  .media-card,
  .lesson-node {
    min-height: 44px;
    padding-top: max(44px - 1.4em, 4px);
    padding-bottom: max(44px - 1.4em, 4px);
  }

  /* Remove hover effects, use active states */
  .btn:hover {
    filter: brightness(1.05);
  }

  .btn:active {
    filter: brightness(0.95);
    transform: scale(0.98);
  }

  /* Disable hover states for tooltips, use focus instead */
  .btn-icon:hover {
    background: rgba(59, 130, 246, 0.15);
  }

  /* Better spacing for touch */
  .glass-card { margin-bottom: 12px; }

  /* Swipe-friendly list items */
  .student-card,
  .lesson-node,
  .media-card {
    margin-bottom: 8px;
  }

  /* Larger text for readability on mobile */
  input[type="text"],
  input[type="email"],
  input[type="password"],
  textarea {
    font-size: 16px;
  }
}

/* High resolution / Retina display optimizations */
@media (-webkit-min-device-pixel-ratio: 2), (min-resolution: 192dpi) {
  /* Thinner borders for crisp appearance */
  .glass-card,
  .btn,
  .form-control {
    border-width: 0.5px;
  }

  /* Slightly bolder fonts for better readability */
  h1, h2, h3 { font-weight: 800; }
  .btn { font-weight: 700; }
}

/* Dark mode improvements for mobile */
@media (prefers-color-scheme: dark) {
  body {
    background-color: var(--bg-dark);
  }

  .glass-card {
    background: rgba(30, 41, 59, 0.9);
  }

  .form-control {
    background: rgba(0, 0, 0, 0.4);
  }
}

/* Light mode improvements */
@media (prefers-color-scheme: light) {
  .form-control {
    background: rgba(255, 255, 255, 0.9);
    color: #1e293b;
  }
}

/* Orientation changes */
@media (orientation: landscape) {
  body {
    overflow-y: auto;
  }

  .content-area {
    padding-top: 60px;
    padding-bottom: 60px;
  }
}

@media (orientation: portrait) {
  .content-area {
    padding-top: 80px;
    padding-bottom: 100px;
  }
}

/* Wide phones (480px+) */
@media (min-width: 480px) {
  .hide-mobile {
    display: inline-block !important;
  }
}

/* Performance optimization helpers */
.lazy-load {
  background: rgba(255, 255, 255, 0.05);
  animation: skeleton-loading 1.2s infinite;
}

@keyframes skeleton-loading {
  0% { opacity: 0.6; }
  50% { opacity: 0.9; }
  100% { opacity: 0.6; }
}

/* Print optimization across all views */
@media print {
  .top-nav,
  .main-nav,
  .btn-icon,
  .options-overlay,
  .login-overlay,
  .filter-bar,
  .sort-controls,
  .actions-bar,
  .sidebar-toggle,
  .btn,
  button,
  input,
  select,
  .hide-print {
    display: none !important;
  }

  body {
    background: #ffffff !important;
    color: #0f172a !important;
    font-size: 10pt;
  }

  .content-area,
  .app-wrapper {
    padding: 0 !important;
    margin: 0 !important;
    max-width: 100% !important;
  }

  .glass-card {
    background: #ffffff !important;
    border: 1px solid #cbd5e1 !important;
    box-shadow: none !important;
    backdrop-filter: none !important;
    page-break-inside: avoid;
  }

  table {
    width: 100% !important;
    border-collapse: collapse !important;
    color: #0f172a !important;
  }

  th {
    background: #f1f5f9 !important;
    color: #0f172a !important;
    font-weight: 800 !important;
    border: 1px solid #94a3b8 !important;
  }

  td {
    border: 1px solid #cbd5e1 !important;
    color: #0f172a !important;
  }

  tr {
    page-break-inside: avoid !important;
  }
}

/* =========================================================
   INTERACTIVE SIMULATION LABS & CANVAS VIEWPORT STYLES
   ========================================================= */
.sim-lab-layout {
  display: grid;
  grid-template-columns: 1.4fr 1fr;
  gap: 20px;
  align-items: stretch;
}

@media (max-width: 900px) {
  .sim-lab-layout {
    grid-template-columns: 1fr;
  }
}

.sim-canvas-viewport {
  background: #0f172a;
  border-radius: 14px;
  border: 1px solid rgba(255, 255, 255, 0.12);
  display: flex;
  align-items: center;
  justify-content: center;
  overflow: hidden;
  position: relative;
  box-shadow: 0 10px 30px rgba(0,0,0,0.5);
}

.sim-canvas-viewport canvas {
  width: 100%;
  height: auto;
  max-height: 480px;
  display: block;
}

.sim-control-group {
  margin-bottom: 12px;
}

.sim-control-group label {
  font-size: 13px;
  font-weight: 600;
  display: flex;
  justify-content: space-between;
  margin-bottom: 6px;
  color: var(--text-main);
}

.sim-val {
  font-family: monospace;
  font-weight: 700;
  color: var(--primary);
}

.sim-slider {
  accent-color: var(--primary);
  width: 100%;
  cursor: pointer;
}

.sim-stat-card {
  background: rgba(15, 23, 42, 0.6);
  border: 1px solid rgba(255, 255, 255, 0.08);
  border-radius: 12px;
  padding: 14px;
  margin-top: 14px;
}

.sim-metric {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 13px;
}

.metric-label {
  color: var(--text-muted);
}

.metric-val {
  font-weight: 700;
}

.sim-progress-track {
  width: 110px;
  height: 8px;
  background: rgba(255, 255, 255, 0.1);
  border-radius: 4px;
  overflow: hidden;
  margin: 0 8px;
}

.sim-progress-fill {
  height: 100%;
  transition: width 0.3s ease;
}

.sim-challenge-card {
  background: rgba(59, 130, 246, 0.08);
  border: 1px solid rgba(59, 130, 246, 0.25);
  border-radius: 12px;
  padding: 14px;
  margin-top: 14px;
}

.sim-challenge-card h4 {
  font-size: 14px;
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.sim-challenge-card p {
  font-size: 13px;
  line-height: 1.5;
  color: var(--text-main);
}

.sim-answer-hint {
  margin-top: 8px;
  padding-top: 8px;
  border-top: 1px solid rgba(255, 255, 255, 0.06);
  color: var(--text-muted);
}

.sim-tab-row {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
}

/* 4 PICS 1 WORD LETTER TILES */
.tile-slots-container {
  display: flex;
  justify-content: center;
  gap: 10px;
  margin: 20px 0;
  flex-wrap: wrap;
}

.letter-slot {
  width: 52px;
  height: 58px;
  background: rgba(30, 41, 59, 0.9);
  border: 2px solid var(--primary);
  border-radius: 12px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 26px;
  font-weight: 800;
  color: #fff;
  box-shadow: 0 4px 15px rgba(0,0,0,0.3);
  cursor: pointer;
  transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
  user-select: none;
}

.letter-slot:hover {
  transform: translateY(-2px);
  border-color: #60a5fa;
}

.letter-slot.filled {
  background: linear-gradient(135deg, #2563eb, #1d4ed8);
  border-color: #93c5fd;
  animation: popIn 0.2s ease-out;
}

.letter-keyboard-grid {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: 8px;
  max-width: 440px;
  margin: 0 auto;
}

.letter-key-btn {
  height: 48px;
  background: rgba(255, 255, 255, 0.08);
  border: 1px solid rgba(255, 255, 255, 0.15);
  border-radius: 10px;
  color: #fff;
  font-size: 20px;
  font-weight: 700;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.15s ease;
  user-select: none;
}

.letter-key-btn:hover {
  background: var(--primary);
  border-color: var(--primary);
  transform: scale(1.05);
}

.letter-key-btn.used {
  opacity: 0.25;
  pointer-events: none;
}

@keyframes popIn {
  from { transform: scale(0.8); opacity: 0; }
  to { transform: scale(1); opacity: 1; }
}

/* SCOREBOARD QUICK POINT BUTTONS */
.score-btn-group {
  display: flex;
  gap: 4px;
}

.btn-point-quick {
  padding: 4px 8px;
  font-size: 11px;
  font-weight: 700;
  border-radius: 6px;
  border: none;
  cursor: pointer;
  transition: transform 0.15s, opacity 0.15s;
  color: #fff;
}

.btn-point-quick:hover {
  transform: translateY(-1px);
}

.btn-point-plus1 { background: #10b981; }
.btn-point-plus3 { background: #3b82f6; }
.btn-point-plus5 { background: #8b5cf6; }
.btn-point-minus1 { background: rgba(239, 68, 68, 0.7); }

/* FLASH QUIZ MULTIPLE CHOICE CARDS */
.choice-cards-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  margin-top: 16px;
}

@media (max-width: 600px) {
  .choice-cards-grid {
    grid-template-columns: 1fr;
  }
}

.choice-card {
  background: rgba(255, 255, 255, 0.05);
  border: 2px solid rgba(255, 255, 255, 0.12);
  border-radius: 12px;
  padding: 16px;
  font-size: 15px;
  font-weight: 600;
  color: var(--text-main);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 12px;
  transition: all 0.2s ease;
  text-align: left;
}

.choice-card:hover {
  background: rgba(59, 130, 246, 0.15);
  border-color: var(--primary);
  transform: translateY(-2px);
}

.choice-card.correct {
  background: rgba(16, 185, 129, 0.25) !important;
  border-color: #10b981 !important;
  color: #6ee7b7 !important;
}

.choice-card.wrong {
  background: rgba(239, 68, 68, 0.25) !important;
  border-color: #ef4444 !important;
  color: #fca5a5 !important;
}

.choice-letter {
  width: 32px;
  height: 32px;
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.1);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 14px;
  font-weight: 800;
  flex-shrink: 0;
}

.flash-timer-track {
  width: 100%;
  height: 6px;
  background: rgba(255, 255, 255, 0.1);
  border-radius: 3px;
  overflow: hidden;
  margin-bottom: 12px;
}

.flash-timer-bar {
  height: 100%;
  background: linear-gradient(90deg, #10b981, #f59e0b, #ef4444);
  width: 100%;
  transition: width 1s linear;
}

/* === Visual Slide Decks Showcase & Index Slide Viewer === */
.deck-showcase-section {
  margin-top: 16px;
  margin-bottom: 24px;
}

.deck-filter-pills {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  justify-content: center;
  margin: 12px 0 16px 0;
}

.deck-filter-pill {
  background: rgba(255, 255, 255, 0.06);
  border: 1px solid var(--glass-border);
  color: var(--text-muted);
  padding: 6px 14px;
  border-radius: 20px;
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s ease;
  display: flex;
  align-items: center;
  gap: 6px;
}

.deck-filter-pill:hover {
  background: rgba(255, 255, 255, 0.12);
  color: #fff;
  border-color: rgba(255, 255, 255, 0.2);
}

.deck-filter-pill.active {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: #fff;
  border-color: transparent;
  box-shadow: 0 4px 14px rgba(59, 130, 246, 0.35);
}

.deck-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 16px;
  margin: 16px 0;
}

.deck-card {
  background: var(--bg-card);
  border: 1px solid var(--glass-border);
  border-radius: 16px;
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: transform 0.25s ease, box-shadow 0.25s ease, border-color 0.25s ease;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.25);
}

.deck-card:hover {
  transform: translateY(-4px);
  border-color: rgba(59, 130, 246, 0.5);
  box-shadow: 0 12px 30px rgba(0, 0, 0, 0.4), 0 0 20px rgba(59, 130, 246, 0.2);
}

.deck-thumb-wrap {
  position: relative;
  width: 100%;
  aspect-ratio: 16 / 9;
  background: #020617;
  overflow: hidden;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
}

.deck-thumb-img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.3s ease;
}

.deck-card:hover .deck-thumb-img {
  transform: scale(1.04);
}

.deck-overlay-badge {
  position: absolute;
  bottom: 8px;
  right: 8px;
  background: rgba(15, 23, 42, 0.85);
  backdrop-filter: blur(6px);
  color: #f8fafc;
  padding: 3px 8px;
  border-radius: 6px;
  font-size: 11px;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 5px;
  border: 1px solid rgba(255, 255, 255, 0.1);
  box-shadow: 0 2px 6px rgba(0,0,0,0.4);
}

.deck-format-badge {
  position: absolute;
  top: 8px;
  left: 8px;
  padding: 3px 8px;
  border-radius: 6px;
  font-size: 11px;
  font-weight: 700;
  display: flex;
  align-items: center;
  gap: 4px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.4);
}

.badge-pdf {
  background: rgba(239, 68, 68, 0.9);
  color: #ffffff;
}

.badge-pptx {
  background: rgba(249, 115, 22, 0.9);
  color: #ffffff;
}

.deck-content {
  padding: 14px;
  display: flex;
  flex-direction: column;
  flex: 1;
}

.deck-title {
  font-size: 15px;
  font-weight: 700;
  color: var(--text-main);
  line-height: 1.35;
  margin-bottom: 6px;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.deck-meta {
  font-size: 12px;
  color: var(--text-muted);
  display: flex;
  gap: 8px;
  align-items: center;
  flex-wrap: wrap;
  margin-bottom: 12px;
}

.deck-meta-tag {
  background: rgba(255, 255, 255, 0.06);
  padding: 2px 7px;
  border-radius: 4px;
  border: 1px solid rgba(255, 255, 255, 0.08);
}

.deck-actions {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  margin-top: auto;
}

.slide-nav-btn {
  position: absolute;
  top: 50%;
  transform: translateY(-50%);
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: rgba(15, 23, 42, 0.75);
  border: 1px solid rgba(255, 255, 255, 0.2);
  color: #ffffff;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  font-size: 18px;
  transition: background 0.2s, transform 0.2s;
  z-index: 10;
}

.slide-nav-btn:hover {
  background: var(--primary);
  transform: translateY(-50%) scale(1.1);
}

.slide-nav-btn.prev { left: 14px; }
.slide-nav-btn.next { right: 14px; }

.filmstrip-thumb {
  width: 76px;
  height: 44px;
  border-radius: 6px;
  border: 2px solid transparent;
  cursor: pointer;
  object-fit: cover;
  opacity: 0.6;
  transition: all 0.2s;
  flex-shrink: 0;
  background: #000;
}

.filmstrip-thumb:hover {
  opacity: 0.9;
  border-color: rgba(255, 255, 255, 0.4);
}

.filmstrip-thumb.active {
  opacity: 1;
  border-color: var(--primary);
  box-shadow: 0 0 10px rgba(59, 130, 246, 0.5);
}