/* ===== CSS VARIABLES & THEME ===== */
:root {
  --bg: #0d0f1a;
  --surface: #151829;
  --surface-2: #1c2038;
  --surface-3: #242844;
  --border: #2d3154;
  --text: #e2e8f0;
  --text-muted: #94a3b8;
  --text-faint: #64748b;
  --primary: #8b5cf6;
  --primary-hover: #7c3aed;
  --primary-glow: rgba(139, 92, 246, 0.3);
  --secondary: #06b6d4;
  --secondary-glow: rgba(6, 182, 212, 0.2);
  --success: #10b981;
  --error: #ef4444;
  --warning: #f59e0b;
  --code-bg: #0f1120;
  --code-border: #252947;
  --sidebar-w: 300px;
  --topbar-h: 60px;
  --font-body: 'Inter', system-ui, -apple-system, sans-serif;
  --font-code: 'JetBrains Mono', 'Fira Code', monospace;
  --radius: 10px;
  --radius-sm: 6px;
}

[data-theme="light"] {
  --bg: #f8f9fc;
  --surface: #ffffff;
  --surface-2: #f1f3f9;
  --surface-3: #e8ebf4;
  --border: #d1d5e4;
  --text: #1e1e2e;
  --text-muted: #5b6078;
  --text-faint: #8b92a8;
  --code-bg: #f0f2f8;
  --code-border: #d4d8e8;
  --primary-glow: rgba(139, 92, 246, 0.15);
  --secondary-glow: rgba(6, 182, 212, 0.1);
}

/* ===== RESET & BASE ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

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

body {
  font-family: var(--font-body);
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  overflow-x: hidden;
  transition: background 0.3s, color 0.3s;
}

/* ===== SCROLLBAR ===== */
::-webkit-scrollbar { width: 8px; height: 8px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: var(--text-faint); }

/* ===== TOPBAR ===== */
.topbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--topbar-h);
  background: var(--surface);
  border-bottom: 1px solid var(--border);
  display: flex;
  align-items: center;
  padding: 0 20px;
  z-index: 100;
  gap: 16px;
  backdrop-filter: blur(12px);
}

.topbar-logo {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text);
  white-space: nowrap;
  flex-shrink: 0;
}

.topbar-logo svg { flex-shrink: 0; }

.topbar-logo .logo-accent { color: var(--primary); }

.hamburger {
  display: none;
  background: none;
  border: none;
  color: var(--text);
  cursor: pointer;
  padding: 4px;
  flex-shrink: 0;
}

.topbar-center { flex: 1; display: flex; align-items: center; justify-content: center; gap: 16px; min-width: 0; }

.xp-display {
  display: flex;
  align-items: center;
  gap: 10px;
  font-size: 0.85rem;
  font-weight: 600;
  white-space: nowrap;
}

.xp-bar-container {
  width: 180px;
  height: 8px;
  background: var(--surface-2);
  border-radius: 4px;
  overflow: hidden;
  position: relative;
}

.xp-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--secondary));
  border-radius: 4px;
  transition: width 0.6s cubic-bezier(0.22, 1, 0.36, 1);
  position: relative;
}

.xp-bar-fill::after {
  content: '';
  position: absolute;
  right: 0;
  top: 0;
  bottom: 0;
  width: 20px;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.3));
  animation: xpShimmer 2s infinite;
}

@keyframes xpShimmer {
  0%, 100% { opacity: 0; }
  50% { opacity: 1; }
}

.level-badge {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  color: #fff;
  padding: 3px 10px;
  border-radius: 12px;
  font-size: 0.75rem;
  font-weight: 700;
  white-space: nowrap;
  text-transform: uppercase;
  letter-spacing: 0.03em;
}

.topbar-actions { display: flex; align-items: center; gap: 8px; flex-shrink: 0; }

.topbar-btn {
  background: var(--surface-2);
  border: 1px solid var(--border);
  color: var(--text-muted);
  padding: 6px 12px;
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 0.8rem;
  font-family: var(--font-body);
  display: flex;
  align-items: center;
  gap: 6px;
  transition: all 0.2s;
  white-space: nowrap;
}

.topbar-btn:hover { background: var(--surface-3); color: var(--text); border-color: var(--primary); }

.topbar-btn kbd {
  font-family: var(--font-body);
  font-size: 0.7rem;
  background: var(--bg);
  padding: 1px 5px;
  border-radius: 3px;
  border: 1px solid var(--border);
}

/* ===== SIDEBAR ===== */
.sidebar {
  position: fixed;
  top: var(--topbar-h);
  left: 0;
  width: var(--sidebar-w);
  height: calc(100vh - var(--topbar-h));
  background: var(--surface);
  border-right: 1px solid var(--border);
  overflow-y: auto;
  z-index: 90;
  padding: 16px 0;
  transition: transform 0.3s cubic-bezier(0.22, 1, 0.36, 1);
}

.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.5);
  z-index: 89;
}

.overall-progress {
  padding: 0 16px 16px;
  border-bottom: 1px solid var(--border);
  margin-bottom: 8px;
}

.overall-progress-label {
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-bottom: 6px;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.overall-bar {
  width: 100%;
  height: 6px;
  background: var(--surface-2);
  border-radius: 3px;
  overflow: hidden;
}

.overall-bar-fill {
  height: 100%;
  background: linear-gradient(90deg, var(--primary), var(--success));
  border-radius: 3px;
  transition: width 0.5s;
}

.overall-pct {
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-top: 4px;
  text-align: right;
}

.track-nav-item {
  padding: 10px 16px;
  cursor: pointer;
  transition: background 0.15s;
  border-left: 3px solid transparent;
}

.track-nav-item:hover { background: var(--surface-2); }
.track-nav-item.active { background: var(--surface-2); border-left-color: var(--primary); }

.track-nav-header {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--text);
  margin-bottom: 6px;
}

.track-nav-header .track-icon { font-size: 1rem; }

.track-progress-bar {
  width: 100%;
  height: 4px;
  background: var(--surface-3);
  border-radius: 2px;
  overflow: hidden;
}

.track-progress-fill {
  height: 100%;
  background: var(--primary);
  border-radius: 2px;
  transition: width 0.4s;
}

.track-progress-text {
  font-size: 0.7rem;
  color: var(--text-faint);
  margin-top: 3px;
}

.track-lessons {
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s;
}

.track-nav-item.active .track-lessons { max-height: 800px; }

.lesson-nav-item {
  padding: 5px 16px 5px 32px;
  font-size: 0.8rem;
  color: var(--text-muted);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 8px;
  transition: color 0.15s;
}

.lesson-nav-item:hover { color: var(--text); }
.lesson-nav-item.current { color: var(--primary); font-weight: 600; }
.lesson-nav-item.completed { color: var(--success); }

.lesson-nav-check {
  width: 14px;
  height: 14px;
  border: 1.5px solid var(--border);
  border-radius: 50%;
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.6rem;
}

.lesson-nav-item.completed .lesson-nav-check {
  background: var(--success);
  border-color: var(--success);
  color: #fff;
}

.lesson-nav-item.current .lesson-nav-check { border-color: var(--primary); }

.sidebar-quiz-btn {
  display: block;
  margin: 8px 16px 8px 32px;
  padding: 5px 12px;
  background: var(--surface-3);
  border: 1px solid var(--border);
  color: var(--text-muted);
  border-radius: var(--radius-sm);
  font-size: 0.75rem;
  cursor: pointer;
  transition: all 0.2s;
  text-align: center;
  font-family: var(--font-body);
}

.sidebar-quiz-btn:hover { border-color: var(--primary); color: var(--primary); }
.sidebar-quiz-btn.completed { background: var(--success); color: #fff; border-color: var(--success); }

/* ===== MAIN CONTENT ===== */
.main {
  margin-left: var(--sidebar-w);
  margin-top: var(--topbar-h);
  min-height: calc(100vh - var(--topbar-h));
  padding: 40px 48px;
  max-width: 900px;
}

.lesson-header {
  margin-bottom: 32px;
}

.lesson-breadcrumb {
  font-size: 0.8rem;
  color: var(--text-faint);
  margin-bottom: 8px;
}

.lesson-breadcrumb span { color: var(--primary); }

.lesson-title {
  font-size: 1.8rem;
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 8px;
  background: linear-gradient(135deg, var(--text), var(--primary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.lesson-meta {
  font-size: 0.8rem;
  color: var(--text-faint);
  display: flex;
  gap: 16px;
}

/* Lesson content typography */
.lesson-content h2 {
  font-size: 1.3rem;
  font-weight: 700;
  margin: 32px 0 12px;
  color: var(--text);
}

.lesson-content h3 {
  font-size: 1.1rem;
  font-weight: 600;
  margin: 24px 0 10px;
  color: var(--text);
}

.lesson-content p {
  margin-bottom: 16px;
  color: var(--text);
  line-height: 1.7;
}

.lesson-content ul, .lesson-content ol {
  margin-bottom: 16px;
  padding-left: 24px;
}

.lesson-content li {
  margin-bottom: 6px;
  line-height: 1.6;
}

.lesson-content strong { color: var(--primary); font-weight: 600; }

.lesson-content em { color: var(--secondary); font-style: normal; }

.inline-code {
  font-family: var(--font-code);
  font-size: 0.85em;
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  padding: 1px 6px;
  border-radius: 4px;
  color: var(--secondary);
}

/* Code blocks */
.code-block {
  position: relative;
  margin: 16px 0 24px;
  border-radius: var(--radius);
  border: 1px solid var(--code-border);
  overflow: hidden;
}

.code-block-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 6px 14px;
  background: var(--surface-2);
  border-bottom: 1px solid var(--code-border);
  font-size: 0.75rem;
}

.code-lang {
  color: var(--text-faint);
  font-family: var(--font-code);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.copy-btn {
  background: none;
  border: 1px solid var(--border);
  color: var(--text-muted);
  padding: 3px 10px;
  border-radius: 4px;
  cursor: pointer;
  font-size: 0.72rem;
  font-family: var(--font-body);
  transition: all 0.2s;
}

.copy-btn:hover { color: var(--text); border-color: var(--primary); }
.copy-btn.copied { color: var(--success); border-color: var(--success); }

.code-block pre {
  padding: 16px;
  overflow-x: auto;
  background: var(--code-bg);
  font-family: var(--font-code);
  font-size: 0.84rem;
  line-height: 1.6;
  tab-size: 2;
  color: var(--text);
}

/* Syntax highlighting tokens */
.tok-kw { color: #c678dd; }
.tok-str { color: #98c379; }
.tok-num { color: #d19a66; }
.tok-cm { color: #5c6370; font-style: italic; }
.tok-fn { color: #61afef; }
.tok-op { color: #56b6c2; }
.tok-type { color: #e5c07b; }
.tok-dec { color: #c678dd; }
.tok-prop { color: #e06c75; }
.tok-punc { color: #abb2bf; }

/* Info/warning boxes */
.info-box {
  padding: 16px 20px;
  border-radius: var(--radius);
  margin: 20px 0;
  border-left: 4px solid;
  font-size: 0.9rem;
}

.info-box.tip { background: rgba(16, 185, 129, 0.08); border-color: var(--success); }
.info-box.warning { background: rgba(245, 158, 11, 0.08); border-color: var(--warning); }
.info-box.info { background: rgba(139, 92, 246, 0.08); border-color: var(--primary); }
.info-box.danger { background: rgba(239, 68, 68, 0.08); border-color: var(--error); }

.info-box-title {
  font-weight: 700;
  margin-bottom: 4px;
  font-size: 0.85rem;
}

.info-box.tip .info-box-title { color: var(--success); }
.info-box.warning .info-box-title { color: var(--warning); }
.info-box.info .info-box-title { color: var(--primary); }
.info-box.danger .info-box-title { color: var(--error); }

/* Key takeaways */
.takeaways {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin: 28px 0;
}

.takeaways-title {
  font-size: 0.85rem;
  font-weight: 700;
  color: var(--primary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 10px;
}

.takeaways ul { padding-left: 18px; }
.takeaways li { margin-bottom: 4px; font-size: 0.9rem; }

/* Comparison tables */
.lesson-content table {
  width: 100%;
  border-collapse: collapse;
  margin: 16px 0 24px;
  font-size: 0.88rem;
}

.lesson-content th {
  background: var(--surface-2);
  padding: 10px 14px;
  text-align: left;
  font-weight: 600;
  border: 1px solid var(--border);
  font-size: 0.82rem;
  text-transform: uppercase;
  letter-spacing: 0.03em;
  color: var(--text-muted);
}

.lesson-content td {
  padding: 10px 14px;
  border: 1px solid var(--border);
  vertical-align: top;
}

/* Mark complete button */
.lesson-complete-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 28px;
  background: linear-gradient(135deg, var(--primary), var(--primary-hover));
  color: #fff;
  border: none;
  border-radius: var(--radius);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  margin-top: 32px;
  font-family: var(--font-body);
  transition: all 0.3s;
  box-shadow: 0 4px 15px var(--primary-glow);
}

.lesson-complete-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 25px var(--primary-glow);
}

.lesson-complete-btn.completed {
  background: var(--success);
  box-shadow: none;
  cursor: default;
}

.lesson-complete-btn.completed:hover { transform: none; }

/* Navigation between lessons */
.lesson-nav {
  display: flex;
  justify-content: space-between;
  margin-top: 24px;
  padding-top: 24px;
  border-top: 1px solid var(--border);
}

.lesson-nav-btn {
  padding: 8px 16px;
  background: var(--surface-2);
  border: 1px solid var(--border);
  color: var(--text-muted);
  border-radius: var(--radius-sm);
  cursor: pointer;
  font-size: 0.85rem;
  font-family: var(--font-body);
  transition: all 0.2s;
}

.lesson-nav-btn:hover { border-color: var(--primary); color: var(--text); }
.lesson-nav-btn:disabled { opacity: 0.3; cursor: default; }
.lesson-nav-btn:disabled:hover { border-color: var(--border); color: var(--text-muted); }

/* ===== QUIZ ===== */
.quiz-container {
  margin: 24px 0;
}

.quiz-question {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin-bottom: 20px;
}

.quiz-question-text {
  font-weight: 600;
  margin-bottom: 14px;
  font-size: 1rem;
}

.quiz-option {
  display: block;
  width: 100%;
  text-align: left;
  padding: 10px 16px;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text);
  cursor: pointer;
  margin-bottom: 8px;
  font-size: 0.9rem;
  font-family: var(--font-body);
  transition: all 0.2s;
}

.quiz-option:hover:not(.selected) { border-color: var(--primary); background: var(--surface-3); }
.quiz-option.correct { border-color: var(--success); background: rgba(16,185,129,0.1); color: var(--success); }
.quiz-option.incorrect { border-color: var(--error); background: rgba(239,68,68,0.1); color: var(--error); }
.quiz-option.show-correct { border-color: var(--success); background: rgba(16,185,129,0.08); }

.quiz-explanation {
  margin-top: 8px;
  padding: 10px 14px;
  background: var(--surface-3);
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  color: var(--text-muted);
  display: none;
}

.quiz-explanation.visible { display: block; }

.quiz-score {
  text-align: center;
  padding: 24px;
  font-size: 1.2rem;
  font-weight: 700;
}

/* ===== SEARCH MODAL ===== */
.search-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.6);
  z-index: 200;
  justify-content: center;
  padding-top: 15vh;
  backdrop-filter: blur(4px);
}

.search-overlay.open { display: flex; }

.search-modal {
  width: 560px;
  max-width: 90vw;
  max-height: 60vh;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: 0 20px 60px rgba(0,0,0,0.4);
  overflow: hidden;
  display: flex;
  flex-direction: column;
}

.search-input-wrap {
  display: flex;
  align-items: center;
  padding: 14px 18px;
  border-bottom: 1px solid var(--border);
  gap: 10px;
}

.search-input-wrap svg { color: var(--text-muted); flex-shrink: 0; }

.search-input {
  flex: 1;
  background: none;
  border: none;
  color: var(--text);
  font-size: 1rem;
  font-family: var(--font-body);
  outline: none;
}

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

.search-results {
  overflow-y: auto;
  max-height: 400px;
}

.search-result-item {
  padding: 12px 18px;
  cursor: pointer;
  border-bottom: 1px solid var(--border);
  transition: background 0.1s;
}

.search-result-item:hover { background: var(--surface-2); }

.search-result-track {
  font-size: 0.72rem;
  color: var(--primary);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.search-result-title {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text);
}

.search-empty {
  padding: 32px;
  text-align: center;
  color: var(--text-faint);
  font-size: 0.9rem;
}

/* ===== ACHIEVEMENTS PANEL ===== */
.achievements-btn {
  position: fixed;
  bottom: 24px;
  right: 24px;
  width: 52px;
  height: 52px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  border: none;
  border-radius: 50%;
  color: #fff;
  font-size: 1.4rem;
  cursor: pointer;
  z-index: 80;
  box-shadow: 0 4px 20px var(--primary-glow);
  transition: transform 0.2s;
  display: flex;
  align-items: center;
  justify-content: center;
}

.achievements-btn:hover { transform: scale(1.1); }

.achievements-panel {
  display: none;
  position: fixed;
  bottom: 90px;
  right: 24px;
  width: 340px;
  max-height: 70vh;
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: 0 10px 40px rgba(0,0,0,0.3);
  z-index: 80;
  overflow-y: auto;
  padding: 20px;
}

.achievements-panel.open { display: block; }

.achievements-panel h3 {
  font-size: 1rem;
  font-weight: 700;
  margin-bottom: 16px;
  color: var(--text);
}

.achievement-item {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 10px 0;
  border-bottom: 1px solid var(--border);
}

.achievement-item:last-child { border-bottom: none; }

.achievement-icon {
  width: 36px;
  height: 36px;
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  background: var(--surface-2);
  flex-shrink: 0;
}

.achievement-item.unlocked .achievement-icon {
  background: linear-gradient(135deg, var(--primary), var(--secondary));
}

.achievement-name {
  font-weight: 600;
  font-size: 0.85rem;
  color: var(--text);
}

.achievement-desc {
  font-size: 0.75rem;
  color: var(--text-muted);
}

.achievement-item:not(.unlocked) {
  opacity: 0.4;
}

/* ===== TOAST ===== */
.toast-container {
  position: fixed;
  top: 80px;
  right: 20px;
  z-index: 300;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.toast {
  background: var(--surface);
  border: 1px solid var(--primary);
  border-radius: var(--radius);
  padding: 14px 20px;
  box-shadow: 0 8px 30px rgba(0,0,0,0.3);
  display: flex;
  align-items: center;
  gap: 10px;
  animation: toastIn 0.4s cubic-bezier(0.22, 1, 0.36, 1);
  max-width: 340px;
}

.toast.exit { animation: toastOut 0.3s forwards; }

@keyframes toastIn { from { transform: translateX(120%); opacity: 0; } to { transform: translateX(0); opacity: 1; } }
@keyframes toastOut { to { transform: translateX(120%); opacity: 0; } }

.toast-icon { font-size: 1.2rem; }
.toast-text { font-size: 0.85rem; font-weight: 500; }

/* ===== LEVEL UP MODAL ===== */
.levelup-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.7);
  z-index: 400;
  justify-content: center;
  align-items: center;
  backdrop-filter: blur(6px);
}

.levelup-overlay.open { display: flex; }

.levelup-modal {
  background: var(--surface);
  border: 2px solid var(--primary);
  border-radius: 16px;
  padding: 40px 50px;
  text-align: center;
  box-shadow: 0 0 80px var(--primary-glow);
  animation: levelPop 0.5s cubic-bezier(0.22, 1, 0.36, 1);
  max-width: 90vw;
}

@keyframes levelPop { from { transform: scale(0.5); opacity: 0; } to { transform: scale(1); opacity: 1; } }

.levelup-emoji { font-size: 4rem; margin-bottom: 16px; display: block; }
.levelup-title { font-size: 1.6rem; font-weight: 800; color: var(--primary); margin-bottom: 8px; }
.levelup-subtitle { color: var(--text-muted); font-size: 0.95rem; margin-bottom: 24px; }

.levelup-close {
  padding: 10px 32px;
  background: var(--primary);
  color: #fff;
  border: none;
  border-radius: var(--radius-sm);
  font-size: 0.95rem;
  font-weight: 600;
  cursor: pointer;
  font-family: var(--font-body);
}

/* ===== CONFETTI CANVAS ===== */
#confetti-canvas {
  position: fixed;
  inset: 0;
  z-index: 500;
  pointer-events: none;
}

/* ===== WELCOME SCREEN ===== */
.welcome {
  text-align: center;
  padding: 60px 20px;
  max-width: 650px;
  margin: 0 auto;
}

.welcome h1 {
  font-size: 2.4rem;
  font-weight: 800;
  margin-bottom: 16px;
  background: linear-gradient(135deg, var(--primary), var(--secondary));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.welcome p {
  color: var(--text-muted);
  font-size: 1.05rem;
  line-height: 1.7;
  margin-bottom: 32px;
}

.welcome-tracks {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px;
  text-align: left;
}

.welcome-track-card {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px;
  cursor: pointer;
  transition: all 0.2s;
}

.welcome-track-card:hover { border-color: var(--primary); transform: translateY(-2px); }

.welcome-track-card .track-num {
  font-size: 0.7rem;
  color: var(--primary);
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.welcome-track-card .track-name {
  font-weight: 600;
  font-size: 0.9rem;
  margin-top: 2px;
}

/* Pulse animation for live indicator */
.pulse-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  background: var(--success);
  display: inline-block;
  animation: pulse 2s infinite;
}

@keyframes pulse {
  0%, 100% { box-shadow: 0 0 0 0 rgba(16, 185, 129, 0.4); }
  50% { box-shadow: 0 0 0 8px rgba(16, 185, 129, 0); }
}

/* ASCII diagram styling */
.ascii-diagram {
  font-family: var(--font-code);
  font-size: 0.78rem;
  line-height: 1.4;
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: var(--radius);
  padding: 16px;
  overflow-x: auto;
  white-space: pre;
  margin: 16px 0;
  color: var(--secondary);
}

/* ===== RESPONSIVE ===== */
@media (max-width: 768px) {
  .hamburger { display: flex; }
  .sidebar { transform: translateX(-100%); width: 280px; }
  .sidebar.open { transform: translateX(0); }
  .sidebar-overlay.open { display: block; }
  .main { margin-left: 0; padding: 24px 18px; }
  .topbar-btn kbd { display: none; }
  .xp-bar-container { width: 100px; }
  .welcome-tracks { grid-template-columns: 1fr; }
  .lesson-title { font-size: 1.4rem; }
  .welcome h1 { font-size: 1.8rem; }
  .achievements-panel { right: 10px; left: 10px; width: auto; bottom: 84px; }
  .achievements-btn { bottom: 16px; right: 16px; width: 46px; height: 46px; }
}

@media (max-width: 480px) {
  .topbar { padding: 0 12px; gap: 8px; }
  .topbar-logo span { display: none; }
  .level-badge { font-size: 0.65rem; padding: 2px 8px; }
  .main { padding: 16px 14px; }
}