/* ============================================================
   STUDYQUEST — COMPONENTS
   Cards, Buttons, Badges, Progress, Modals, XP Bars
   ============================================================ */

/* ── Buttons ── */
.btn-primary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 12px 24px;
  background: var(--grad-primary);
  color: white;
  font-family: var(--font-body);
  font-size: 14px;
  font-weight: 700;
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  transition: all var(--transition-normal);
  position: relative;
  overflow: hidden;
  letter-spacing: 0.3px;
}

.btn-primary::before {
  content: '';
  position: absolute;
  top: 0; left: -100%;
  width: 100%; height: 100%;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.2), transparent);
  transition: left 0.4s ease;
}

.btn-primary:hover::before { left: 100%; }
.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 8px 24px rgba(124,58,237,0.4); }
.btn-primary:active { transform: translateY(0); }

.btn-secondary {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 20px;
  background: var(--bg-elevated);
  color: var(--text-primary);
  font-family: var(--font-body);
  font-size: 14px;
  font-weight: 600;
  border-radius: var(--radius-md);
  border: 1px solid var(--border-subtle);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.btn-secondary:hover {
  border-color: var(--neon-blue);
  color: var(--neon-blue);
  background: rgba(0,212,255,0.05);
}

.btn-ghost {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 6px 12px;
  color: var(--text-secondary);
  font-size: 13px;
  font-weight: 600;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
  background: none;
  border: none;
  cursor: pointer;
}

.btn-ghost:hover { color: var(--neon-blue); }

.btn-danger {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 10px 20px;
  background: rgba(247,37,133,0.1);
  color: var(--neon-pink);
  font-size: 14px;
  font-weight: 600;
  border-radius: var(--radius-md);
  border: 1px solid rgba(247,37,133,0.3);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.btn-danger:hover { background: rgba(247,37,133,0.2); }

.btn-gold {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  background: var(--grad-gold);
  color: #000;
  font-size: 14px;
  font-weight: 800;
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  transition: all var(--transition-normal);
}

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

.btn-sm { padding: 6px 14px; font-size: 12px; }
.btn-lg { padding: 14px 32px; font-size: 16px; }
.btn-full { width: 100%; }

/* ── Subject Cards ── */
.subject-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: var(--space-lg);
  cursor: pointer;
  transition: all var(--transition-normal);
  position: relative;
  overflow: hidden;
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.subject-card::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 3px;
  background: var(--subject-color, var(--grad-primary));
  border-radius: var(--radius-xl) var(--radius-xl) 0 0;
}

.subject-card::after {
  content: '';
  position: absolute;
  top: -40%;
  right: -20%;
  width: 200px;
  height: 200px;
  background: radial-gradient(circle, var(--subject-glow, rgba(0,212,255,0.08)) 0%, transparent 70%);
  pointer-events: none;
  transition: opacity var(--transition-normal);
}

.subject-card:hover {
  transform: translateY(-4px);
  border-color: var(--subject-border, var(--border-glow));
  box-shadow: var(--shadow-card), 0 0 30px var(--subject-glow, rgba(0,212,255,0.1));
}

.subject-card-top {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
}

.subject-icon-wrap {
  width: 56px;
  height: 56px;
  border-radius: var(--radius-lg);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 28px;
  background: var(--subject-bg, rgba(0,212,255,0.1));
  border: 1px solid var(--subject-border, rgba(0,212,255,0.2));
  flex-shrink: 0;
}

.subject-difficulty {
  display: flex;
  align-items: center;
  gap: 3px;
}

.diff-dot {
  width: 6px;
  height: 6px;
  border-radius: 50%;
  background: var(--border-subtle);
}

.diff-dot.filled { background: var(--subject-color-solid, var(--neon-blue)); }

.subject-name {
  font-family: var(--font-display);
  font-size: 18px;
  font-weight: 800;
  color: var(--text-primary);
  margin-bottom: 2px;
}

.subject-chapters {
  font-size: 12px;
  color: var(--text-muted);
}

.subject-progress-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 12px;
  color: var(--text-secondary);
  margin-bottom: 4px;
}

.subject-progress-bar {
  height: 6px;
  background: var(--border-subtle);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.subject-progress-fill {
  height: 100%;
  background: var(--subject-color, var(--grad-primary));
  border-radius: var(--radius-full);
  transition: width 0.8s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.subject-stats-row {
  display: flex;
  gap: var(--space-md);
}

.subject-stat {
  display: flex;
  align-items: center;
  gap: 4px;
  font-size: 12px;
  color: var(--text-secondary);
}

.subject-stat .s-icon { font-size: 14px; }

.subject-next {
  background: var(--bg-elevated);
  border-radius: var(--radius-sm);
  padding: 8px 12px;
  font-size: 12px;
  color: var(--text-secondary);
  border-left: 2px solid var(--subject-color-solid, var(--neon-blue));
}

.subject-next strong { color: var(--text-primary); display: block; font-size: 13px; }

/* ── Chapter Cards ── */
.chapter-item {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--space-md) var(--space-lg);
  cursor: pointer;
  transition: all var(--transition-normal);
  position: relative;
}

.chapter-item:hover:not(.locked) {
  border-color: var(--border-glow);
  transform: translateX(4px);
  box-shadow: var(--shadow-glow);
}

.chapter-item.locked {
  opacity: 0.5;
  cursor: not-allowed;
  filter: grayscale(0.5);
}

.chapter-item.completed {
  border-color: rgba(57,255,20,0.3);
  background: rgba(57,255,20,0.03);
}

.chapter-item.completed::after {
  content: '✓';
  position: absolute;
  right: var(--space-md);
  top: 50%;
  transform: translateY(-50%);
  color: var(--neon-green);
  font-size: 18px;
  font-weight: 700;
}

.chapter-num {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background: var(--bg-elevated);
  border: 2px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 700;
  color: var(--text-secondary);
  flex-shrink: 0;
  transition: all var(--transition-normal);
}

.chapter-item:hover:not(.locked) .chapter-num {
  border-color: var(--neon-blue);
  color: var(--neon-blue);
  background: rgba(0,212,255,0.1);
}

.chapter-item.completed .chapter-num {
  border-color: var(--neon-green);
  color: var(--neon-green);
  background: rgba(57,255,20,0.1);
}

.chapter-info { flex: 1; }

.chapter-title {
  font-weight: 700;
  font-size: 15px;
  color: var(--text-primary);
  margin-bottom: 2px;
}

.chapter-meta {
  font-size: 12px;
  color: var(--text-muted);
  display: flex;
  gap: var(--space-md);
}

.chapter-progress-mini {
  width: 80px;
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  gap: 4px;
}

.chapter-pct {
  font-size: 12px;
  font-weight: 700;
  color: var(--text-secondary);
}

.chapter-bar {
  width: 100%;
  height: 4px;
  background: var(--border-subtle);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.chapter-bar-fill {
  height: 100%;
  background: var(--grad-primary);
  border-radius: var(--radius-full);
}

.lock-icon {
  font-size: 18px;
  color: var(--text-muted);
  margin-left: auto;
}

/* ── Topic Cards ── */
.topic-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--space-md);
  cursor: pointer;
  transition: all var(--transition-normal);
  display: flex;
  align-items: center;
  gap: var(--space-md);
}

.topic-card:hover:not(.locked) {
  border-color: var(--border-glow);
  background: var(--bg-card-hover);
}

.topic-type-badge {
  padding: 3px 10px;
  border-radius: var(--radius-full);
  font-size: 10px;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  flex-shrink: 0;
}

.type-theory   { background: rgba(0,212,255,0.1);  color: var(--neon-blue);   border: 1px solid rgba(0,212,255,0.2); }
.type-derivation { background: rgba(124,58,237,0.1); color: #a78bfa; border: 1px solid rgba(124,58,237,0.2); }
.type-numerical { background: rgba(255,107,43,0.1); color: var(--neon-orange); border: 1px solid rgba(255,107,43,0.2); }
.type-practice  { background: rgba(57,255,20,0.1);  color: var(--neon-green);  border: 1px solid rgba(57,255,20,0.2); }

.topic-name {
  flex: 1;
  font-size: 14px;
  font-weight: 600;
  color: var(--text-primary);
}

.topic-xp {
  font-size: 12px;
  color: var(--neon-gold);
  font-weight: 700;
  font-family: var(--font-mono);
}

.topic-status {
  font-size: 16px;
}

/* ── Task Items ── */
.task-item {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: 10px 12px;
  background: var(--bg-elevated);
  border-radius: var(--radius-md);
  border: 1px solid var(--border-subtle);
  transition: all var(--transition-fast);
}

.task-item.completed {
  opacity: 0.6;
  border-color: rgba(57,255,20,0.2);
}

.task-checkbox {
  width: 20px;
  height: 20px;
  border-radius: 50%;
  border: 2px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.task-item.completed .task-checkbox {
  background: var(--neon-green);
  border-color: var(--neon-green);
  color: #000;
  font-size: 11px;
}

.task-text {
  flex: 1;
  font-size: 13px;
  color: var(--text-secondary);
}

.task-item.completed .task-text {
  text-decoration: line-through;
  color: var(--text-muted);
}

.task-xp {
  font-size: 11px;
  color: var(--neon-gold);
  font-weight: 700;
  font-family: var(--font-mono);
}

.task-progress-mini {
  display: flex;
  align-items: center;
  gap: 6px;
  font-size: 11px;
  color: var(--text-muted);
}

.task-mini-bar {
  width: 50px;
  height: 3px;
  background: var(--border-subtle);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.task-mini-fill {
  height: 100%;
  background: var(--grad-primary);
  border-radius: var(--radius-full);
}

/* ── Badge Cards ── */
.badge-card {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--space-sm);
  padding: var(--space-md);
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  cursor: pointer;
  transition: all var(--transition-normal);
  text-align: center;
  position: relative;
  overflow: hidden;
}

.badge-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-card);
}

.badge-card.locked {
  opacity: 0.4;
  filter: grayscale(1);
}

.badge-card.rarity-common  { border-color: rgba(160,160,192,0.3); }
.badge-card.rarity-rare    { border-color: rgba(0,212,255,0.3); }
.badge-card.rarity-epic    { border-color: rgba(124,58,237,0.4); }
.badge-card.rarity-legendary { border-color: rgba(255,215,0,0.5); box-shadow: 0 0 16px rgba(255,215,0,0.15); }

.badge-card.rarity-legendary::before {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(135deg, rgba(255,215,0,0.05), transparent);
  pointer-events: none;
}

.badge-icon-wrap {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 28px;
  position: relative;
}

.badge-icon-wrap.rarity-common   { background: rgba(160,160,192,0.1); }
.badge-icon-wrap.rarity-rare     { background: rgba(0,212,255,0.1); }
.badge-icon-wrap.rarity-epic     { background: rgba(124,58,237,0.15); }
.badge-icon-wrap.rarity-legendary { background: rgba(255,215,0,0.15); }

.badge-name {
  font-size: 12px;
  font-weight: 700;
  color: var(--text-primary);
  line-height: 1.2;
}

.badge-rarity {
  font-size: 9px;
  font-weight: 800;
  text-transform: uppercase;
  letter-spacing: 1px;
  padding: 2px 8px;
  border-radius: var(--radius-full);
}

.badge-rarity.common   { background: rgba(160,160,192,0.15); color: #a0a0c0; }
.badge-rarity.rare     { background: rgba(0,212,255,0.15);   color: var(--neon-blue); }
.badge-rarity.epic     { background: rgba(124,58,237,0.15);  color: #a78bfa; }
.badge-rarity.legendary { background: rgba(255,215,0,0.15);  color: var(--neon-gold); }

/* Recent badge mini */
.badge-mini {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  padding: var(--space-md);
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  min-width: 80px;
  text-align: center;
  transition: all var(--transition-fast);
}

.badge-mini:hover { transform: translateY(-2px); }
.badge-mini .badge-emoji { font-size: 28px; }
.badge-mini .badge-mini-name { font-size: 11px; color: var(--text-secondary); font-weight: 600; }

/* ── XP Popup ── */
.xp-popup {
  position: fixed;
  top: 80px;
  right: 24px;
  background: var(--bg-card);
  border: 1px solid rgba(0,212,255,0.3);
  border-radius: var(--radius-lg);
  padding: 10px 20px;
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  font-weight: 700;
  font-size: 16px;
  color: var(--neon-blue);
  z-index: 9999;
  box-shadow: 0 0 20px rgba(0,212,255,0.2);
  animation: xpPopIn 0.4s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.xp-popup.hidden { display: none; }
.xp-icon { font-size: 20px; }

/* ── Toast ── */
#toast-container {
  position: fixed;
  bottom: 24px;
  right: 24px;
  z-index: 9998;
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.toast {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: 12px 20px;
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  font-size: 14px;
  color: var(--text-primary);
  box-shadow: var(--shadow-card);
  animation: toastSlideIn 0.3s ease;
  max-width: 320px;
}

.toast.success { border-color: rgba(57,255,20,0.3); }
.toast.error   { border-color: rgba(247,37,133,0.3); }
.toast.info    { border-color: rgba(0,212,255,0.3); }
.toast.warning { border-color: rgba(255,215,0,0.3); }

/* ── Level Up Overlay ── */
.levelup-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.85);
  z-index: 10000;
  display: flex;
  align-items: center;
  justify-content: center;
  backdrop-filter: blur(8px);
}

.levelup-overlay.hidden { display: none; }

.levelup-content {
  position: relative;
  text-align: center;
}

.levelup-rays {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 400px;
  height: 400px;
  background: conic-gradient(from 0deg, transparent 0deg, rgba(0,212,255,0.1) 10deg, transparent 20deg, rgba(124,58,237,0.1) 30deg, transparent 40deg);
  border-radius: 50%;
  animation: spinRays 4s linear infinite;
}

.levelup-badge {
  position: relative;
  z-index: 1;
  background: var(--bg-card);
  border: 2px solid var(--neon-blue);
  border-radius: var(--radius-xl);
  padding: var(--space-2xl);
  box-shadow: 0 0 60px rgba(0,212,255,0.3);
  animation: levelUpBounce 0.6s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.levelup-icon {
  font-size: 64px;
  display: block;
  margin-bottom: var(--space-md);
  animation: iconPulse 1s ease infinite;
}

.levelup-badge h1 {
  font-family: var(--font-display);
  font-size: 48px;
  font-weight: 900;
  background: var(--grad-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: var(--space-sm);
}

.levelup-badge p {
  color: var(--text-secondary);
  font-size: 18px;
  margin-bottom: var(--space-sm);
}

.levelup-title-text {
  color: var(--neon-gold) !important;
  font-weight: 700 !important;
  font-size: 16px !important;
  margin-bottom: var(--space-lg) !important;
}

/* ── Badge Overlay ── */
.badge-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.85);
  z-index: 10000;
  display: flex;
  align-items: center;
  justify-content: center;
  backdrop-filter: blur(8px);
}

.badge-overlay.hidden { display: none; }

.badge-earned-card {
  background: var(--bg-card);
  border: 2px solid var(--neon-gold);
  border-radius: var(--radius-xl);
  padding: var(--space-2xl);
  text-align: center;
  box-shadow: 0 0 60px rgba(255,215,0,0.3);
  animation: levelUpBounce 0.6s cubic-bezier(0.34, 1.56, 0.64, 1);
  position: relative;
}

.badge-sparkles {
  position: absolute;
  inset: 0;
  pointer-events: none;
  overflow: hidden;
  border-radius: var(--radius-xl);
}

.badge-big-icon {
  font-size: 72px;
  display: block;
  margin-bottom: var(--space-md);
  animation: iconPulse 1s ease infinite;
}

.badge-earned-card h2 {
  font-family: var(--font-display);
  font-size: 32px;
  font-weight: 900;
  background: var(--grad-gold);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin-bottom: var(--space-sm);
}

.badge-earned-card p { color: var(--text-secondary); margin-bottom: var(--space-sm); }

/* ── Modals ── */
.modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.7);
  z-index: 1000;
  display: flex;
  align-items: center;
  justify-content: center;
  backdrop-filter: blur(4px);
  padding: var(--space-md);
}

.modal-overlay.hidden { display: none; }

.modal-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: var(--space-xl);
  position: relative;
  width: 100%;
  max-width: 420px;
  box-shadow: var(--shadow-card);
  animation: modalSlideIn 0.3s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.modal-card h2 {
  font-family: var(--font-display);
  font-size: 22px;
  font-weight: 800;
  margin-bottom: var(--space-lg);
  text-align: center;
}

.modal-close {
  position: absolute;
  top: var(--space-md);
  right: var(--space-md);
  color: var(--text-muted);
  font-size: 18px;
  padding: 4px 8px;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
}

.modal-close:hover { color: var(--text-primary); background: var(--border-subtle); }

/* ── Pomodoro ── */
.pomodoro-card { max-width: 360px; }

.pomodoro-display {
  position: relative;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: var(--space-lg) auto;
  width: 160px;
  height: 160px;
}

.pomodoro-ring {
  position: absolute;
  width: 160px;
  height: 160px;
  transform: rotate(-90deg);
}

.ring-bg {
  fill: none;
  stroke: var(--border-subtle);
  stroke-width: 8;
}

.ring-fill {
  fill: none;
  stroke: url(#pomodoroGrad);
  stroke-width: 8;
  stroke-linecap: round;
  transition: stroke-dashoffset 1s linear;
}

.pomodoro-time {
  font-family: var(--font-mono);
  font-size: 36px;
  font-weight: 700;
  color: var(--text-primary);
  position: relative;
  z-index: 1;
  line-height: 1;
}

.pomodoro-label {
  position: absolute;
  bottom: 20px;
  font-size: 11px;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 1px;
}

.pomodoro-controls {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-md);
  margin-bottom: var(--space-md);
}

.pomodoro-sessions {
  text-align: center;
  margin-bottom: var(--space-md);
}

.pomo-session-label {
  font-size: 12px;
  color: var(--text-muted);
  display: block;
  margin-top: 4px;
}

.pomodoro-modes {
  display: flex;
  gap: var(--space-sm);
  justify-content: center;
}

.pomo-mode {
  padding: 6px 14px;
  border-radius: var(--radius-full);
  font-size: 12px;
  font-weight: 600;
  color: var(--text-muted);
  border: 1px solid var(--border-subtle);
  transition: all var(--transition-fast);
  cursor: pointer;
  background: none;
}

.pomo-mode.active {
  background: rgba(0,212,255,0.1);
  border-color: var(--neon-blue);
  color: var(--neon-blue);
}

/* ── Music Player ── */
.music-card { max-width: 380px; }

.music-visualizer {
  display: flex;
  align-items: flex-end;
  justify-content: center;
  gap: 4px;
  height: 48px;
  margin-bottom: var(--space-lg);
}

.music-visualizer .bar {
  width: 6px;
  background: var(--grad-primary);
  border-radius: 3px;
  height: 8px;
  transition: height 0.1s ease;
}

.music-visualizer.playing .bar {
  animation: musicBar 0.8s ease infinite;
}

.music-visualizer.playing .bar:nth-child(1) { animation-delay: 0s; }
.music-visualizer.playing .bar:nth-child(2) { animation-delay: 0.1s; }
.music-visualizer.playing .bar:nth-child(3) { animation-delay: 0.2s; }
.music-visualizer.playing .bar:nth-child(4) { animation-delay: 0.3s; }
.music-visualizer.playing .bar:nth-child(5) { animation-delay: 0.4s; }
.music-visualizer.playing .bar:nth-child(6) { animation-delay: 0.5s; }
.music-visualizer.playing .bar:nth-child(7) { animation-delay: 0.6s; }
.music-visualizer.playing .bar:nth-child(8) { animation-delay: 0.7s; }

.music-tracks {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  margin-bottom: var(--space-lg);
  max-height: 200px;
  overflow-y: auto;
}

.music-track {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: 8px 12px;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
  border: 1px solid transparent;
}

.music-track:hover { background: var(--bg-elevated); }
.music-track.active {
  background: rgba(0,212,255,0.08);
  border-color: rgba(0,212,255,0.2);
}

.track-icon { font-size: 20px; }
.track-info { flex: 1; }
.track-name { font-size: 13px; font-weight: 600; color: var(--text-primary); }
.track-type { font-size: 11px; color: var(--text-muted); }
.track-active-dot {
  width: 8px; height: 8px;
  border-radius: 50%;
  background: var(--neon-blue);
  animation: pulse 1s ease infinite;
}

.music-controls {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-md);
  margin-bottom: var(--space-md);
}

.music-btn {
  width: 40px; height: 40px;
  border-radius: 50%;
  background: var(--bg-elevated);
  border: 1px solid var(--border-subtle);
  color: var(--text-secondary);
  font-size: 16px;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-fast);
  cursor: pointer;
}

.music-btn:hover { color: var(--neon-blue); border-color: var(--neon-blue); }

.music-btn.play-btn {
  width: 52px; height: 52px;
  background: var(--grad-primary);
  border: none;
  color: white;
  font-size: 18px;
}

.volume-control {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  color: var(--text-muted);
  font-size: 14px;
}

.volume-control input[type="range"] {
  flex: 1;
  accent-color: var(--neon-blue);
  cursor: pointer;
}

/* ── Learning Content Cards ── */
.concept-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-xl);
  padding: var(--space-xl);
  margin-bottom: var(--space-lg);
}

.concept-card h2 {
  font-family: var(--font-display);
  font-size: 24px;
  font-weight: 800;
  margin-bottom: var(--space-md);
  color: var(--text-primary);
}

.definition-box {
  background: rgba(0,212,255,0.05);
  border: 1px solid rgba(0,212,255,0.2);
  border-left: 4px solid var(--neon-blue);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  margin-bottom: var(--space-lg);
  font-size: 16px;
  line-height: 1.8;
  color: var(--text-primary);
}

.formula-box {
  background: rgba(124,58,237,0.05);
  border: 1px solid rgba(124,58,237,0.2);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  text-align: center;
  font-family: var(--font-mono);
  font-size: 20px;
  color: #a78bfa;
  margin-bottom: var(--space-lg);
}

.example-box {
  background: rgba(57,255,20,0.03);
  border: 1px solid rgba(57,255,20,0.15);
  border-radius: var(--radius-md);
  padding: var(--space-md);
  margin-bottom: var(--space-md);
}

.example-box h4 {
  color: var(--neon-green);
  font-size: 12px;
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: var(--space-sm);
}

/* ── MCQ Options ── */
.mcq-options {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
  margin-bottom: var(--space-lg);
}

.mcq-option {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-md) var(--space-lg);
  background: var(--bg-elevated);
  border: 2px solid var(--border-subtle);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
  font-size: 15px;
  color: var(--text-primary);
  text-align: left;
  width: 100%;
}

.mcq-option:hover:not(:disabled) {
  border-color: var(--neon-blue);
  background: rgba(0,212,255,0.05);
}

.mcq-option.selected { border-color: var(--neon-blue); background: rgba(0,212,255,0.08); }
.mcq-option.correct  { border-color: var(--neon-green); background: rgba(57,255,20,0.08); color: var(--neon-green); }
.mcq-option.wrong    { border-color: var(--neon-pink);  background: rgba(247,37,133,0.08); color: var(--neon-pink); }

.option-letter {
  width: 28px; height: 28px;
  border-radius: 50%;
  background: var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 12px;
  font-weight: 700;
  flex-shrink: 0;
}

/* ── Flashcard ── */
.flashcard-container {
  perspective: 1000px;
  width: 100%;
  max-width: 500px;
  margin: 0 auto var(--space-xl);
  height: 280px;
  cursor: pointer;
}

.flashcard {
  width: 100%;
  height: 100%;
  position: relative;
  transform-style: preserve-3d;
  transition: transform 0.6s cubic-bezier(0.34, 1.56, 0.64, 1);
}

.flashcard.flipped { transform: rotateY(180deg); }

.flashcard-front,
.flashcard-back {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  border-radius: var(--radius-xl);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  padding: var(--space-xl);
  text-align: center;
}

.flashcard-front {
  background: var(--bg-card);
  border: 2px solid var(--border-glow);
}

.flashcard-back {
  background: linear-gradient(135deg, rgba(124,58,237,0.1), rgba(0,212,255,0.1));
  border: 2px solid rgba(124,58,237,0.3);
  transform: rotateY(180deg);
}

.flashcard-label {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 1px;
  color: var(--text-muted);
  margin-bottom: var(--space-md);
}

.flashcard-content {
  font-size: 18px;
  font-weight: 600;
  color: var(--text-primary);
  line-height: 1.5;
}

.flashcard-hint {
  margin-top: var(--space-md);
  font-size: 12px;
  color: var(--text-muted);
}

/* ── Progress Charts ── */
.stats-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
  gap: var(--space-md);
  margin-bottom: var(--space-xl);
}

.stat-card {
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--space-lg);
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.stat-card-icon {
  font-size: 28px;
  margin-bottom: var(--space-xs);
}

.stat-card-value {
  font-family: var(--font-display);
  font-size: 32px;
  font-weight: 900;
  background: var(--grad-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  line-height: 1;
}

.stat-card-label {
  font-size: 13px;
  color: var(--text-secondary);
}

.stat-card-change {
  font-size: 12px;
  color: var(--neon-green);
  font-weight: 600;
}

/* ── Leaderboard ── */
.leaderboard-list {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.leaderboard-item {
  display: flex;
  align-items: center;
  gap: var(--space-md);
  padding: var(--space-md) var(--space-lg);
  background: var(--bg-card);
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-lg);
  transition: all var(--transition-fast);
}

.leaderboard-item:hover { border-color: var(--border-glow); }

.leaderboard-item.rank-1 { border-color: rgba(255,215,0,0.4); background: rgba(255,215,0,0.03); }
.leaderboard-item.rank-2 { border-color: rgba(192,192,192,0.4); }
.leaderboard-item.rank-3 { border-color: rgba(205,127,50,0.4); }
.leaderboard-item.is-you { border-color: rgba(0,212,255,0.4); background: rgba(0,212,255,0.03); }

.lb-rank {
  font-family: var(--font-mono);
  font-size: 18px;
  font-weight: 700;
  width: 36px;
  text-align: center;
  flex-shrink: 0;
}

.lb-avatar { font-size: 28px; }

.lb-info { flex: 1; }
.lb-name { font-weight: 700; font-size: 15px; color: var(--text-primary); }
.lb-level { font-size: 12px; color: var(--text-muted); }

.lb-xp {
  font-family: var(--font-mono);
  font-size: 14px;
  font-weight: 700;
  color: var(--neon-gold);
}

/* ── Drag & Drop ── */
.drag-item {
  padding: 10px 16px;
  background: var(--bg-elevated);
  border: 2px solid var(--border-subtle);
  border-radius: var(--radius-md);
  cursor: grab;
  font-size: 14px;
  font-weight: 600;
  color: var(--text-primary);
  transition: all var(--transition-fast);
  user-select: none;
}

.drag-item:hover { border-color: var(--neon-blue); }
.drag-item.dragging { opacity: 0.5; cursor: grabbing; }

.drop-zone {
  min-height: 48px;
  border: 2px dashed var(--border-subtle);
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 13px;
  color: var(--text-muted);
  transition: all var(--transition-fast);
  padding: var(--space-sm);
}

.drop-zone.drag-over {
  border-color: var(--neon-blue);
  background: rgba(0,212,255,0.05);
}

.drop-zone.filled {
  border-style: solid;
  border-color: var(--neon-green);
  background: rgba(57,255,20,0.05);
  color: var(--text-primary);
  font-weight: 600;
}

/* ── Combo Multiplier ── */
.combo-display {
  display: flex;
  align-items: center;
  gap: var(--space-sm);
  padding: 8px 16px;
  background: rgba(255,215,0,0.1);
  border: 1px solid rgba(255,215,0,0.3);
  border-radius: var(--radius-full);
  font-weight: 800;
  font-size: 16px;
  color: var(--neon-gold);
  animation: comboPulse 0.5s ease;
}

/* ── Misc Utilities ── */
.hidden { display: none !important; }
.text-center { text-align: center; }
.text-muted { color: var(--text-muted); }
.text-accent { color: var(--neon-blue); }
.text-gold { color: var(--neon-gold); }
.text-green { color: var(--neon-green); }
.text-pink { color: var(--neon-pink); }

.divider {
  height: 1px;
  background: var(--border-subtle);
  margin: var(--space-lg) 0;
}

.tag {
  display: inline-flex;
  align-items: center;
  padding: 3px 10px;
  border-radius: var(--radius-full);
  font-size: 11px;
  font-weight: 600;
  background: var(--border-subtle);
  color: var(--text-secondary);
}

.empty-state {
  text-align: center;
  padding: var(--space-3xl);
  color: var(--text-muted);
}

.empty-state .empty-icon { font-size: 48px; margin-bottom: var(--space-md); }
.empty-state h3 { font-size: 18px; font-weight: 700; margin-bottom: var(--space-sm); color: var(--text-secondary); }
.empty-state p { font-size: 14px; }

/* SVG gradient defs (hidden) */
.svg-defs { position: absolute; width: 0; height: 0; overflow: hidden; }