/* ═══════════════════════════════════════════════════════════
   COURSES.CSS — Premium Course UI (Udemy/HTB Style)
   ═══════════════════════════════════════════════════════════ */

/* ── Lesson Open Tab Button ── */
.lesson-open-tab {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: 8px;
  color: #555;
  transition: all 0.2s;
  flex-shrink: 0;
  margin-left: auto;
  margin-right: 8px;
}
.lesson-open-tab:hover {
  color: var(--accent);
  background: var(--accent-dim);
}

/* ── Lesson Note (Sarcastic Beginner Note) ── */
.lesson-note {
  background: linear-gradient(135deg, rgba(255,193,7,0.08), rgba(255,152,0,0.05));
  border-left: 3px solid #ffc107;
  border-radius: 0 12px 12px 0;
  padding: 16px 20px;
  margin: 16px 0;
  font-size: 14px;
  line-height: 1.7;
  color: #bbb;
}
.lesson-note strong {
  color: #ffc107;
}

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800;900&family=JetBrains+Mono:wght@400;500;600;700&display=swap');

:root {
  --bg: #050508;
  --bg-2: #0c0c14;
  --bg-3: #12121e;
  --bg-4: #1a1a2e;
  --bg-glass: rgba(12,12,20,0.7);
  --text: #f0f0f0;
  --text-2: #8b949e;
  --text-3: #484f58;
  --accent: #6c63ff;
  --accent-dim: rgba(108,99,255,0.12);
  --green: #00e676;
  --green-dim: rgba(0,230,118,0.1);
  --red: #ff5252;
  --red-dim: rgba(255,82,82,0.1);
  --orange: #ff9800;
  --orange-dim: rgba(255,152,0,0.1);
  --cyan: #00bcd4;
  --cyan-dim: rgba(0,188,212,0.1);
  --yellow: #ffd600;
  --border: rgba(255,255,255,0.06);
  --border-hover: rgba(255,255,255,0.12);
  --glow: rgba(108,99,255,0.15);
  --font-body: 'Inter', -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;
  --ease: cubic-bezier(0.16,1,0.3,1);
  --ease-bounce: cubic-bezier(0.34,1.56,0.64,1);
  --radius: 16px;
  --radius-sm: 10px;
  --radius-xs: 6px;
}

[data-theme="light"] {
  --bg: #f8f9fa; --bg-2: #ffffff; --bg-3: #f0f1f3; --bg-4: #e8e9ec;
  --bg-glass: rgba(255,255,255,0.8); --text: #1a1a2e; --text-2: #555; --text-3: #999;
  --border: rgba(0,0,0,0.08); --border-hover: rgba(0,0,0,0.15);
}

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

html { scroll-behavior: smooth; }

body {
  font-family: var(--font-body);
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

/* ═══ HERO ═══ */
.course-hero {
  position: relative;
  padding: 6rem 2rem 4rem;
  text-align: center;
  overflow: hidden;
  background:
    radial-gradient(ellipse at 20% 50%, rgba(108,99,255,0.1) 0%, transparent 50%),
    radial-gradient(ellipse at 80% 50%, rgba(0,230,118,0.06) 0%, transparent 50%),
    var(--bg);
}
.course-hero::before {
  content: ''; position: absolute; inset: 0;
  background-image:
    linear-gradient(rgba(108,99,255,0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(108,99,255,0.03) 1px, transparent 1px);
  background-size: 50px 50px;
  mask-image: radial-gradient(ellipse at center, black 20%, transparent 70%);
  -webkit-mask-image: radial-gradient(ellipse at center, black 20%, transparent 70%);
}
.course-hero::after {
  content: ''; position: absolute; bottom: 0; left: 0; right: 0; height: 120px;
  background: linear-gradient(to top, var(--bg), transparent);
}

.hero-badge {
  display: inline-flex; align-items: center; gap: 0.5rem;
  padding: 0.4rem 1rem; border-radius: 100px;
  background: var(--accent-dim); border: 1px solid rgba(108,99,255,0.2);
  font-family: var(--font-mono); font-size: 0.65rem; font-weight: 600;
  color: var(--accent); letter-spacing: 0.1em; text-transform: uppercase;
  margin-bottom: 1.5rem;
  animation: heroFadeUp 0.6s var(--ease) 0.1s both;
}
.hero-badge-dot {
  width: 6px; height: 6px; border-radius: 50%;
  background: var(--green); animation: pulse 2s ease infinite;
}
@keyframes pulse { 0%,100%{opacity:1;transform:scale(1)} 50%{opacity:0.5;transform:scale(1.3)} }

.hero-icon {
  font-size: 3.5rem; margin-bottom: 1.25rem;
  animation: heroFadeUp 0.6s var(--ease) 0.2s both;
  filter: drop-shadow(0 0 30px rgba(108,99,255,0.3));
}

.hero-title {
  font-size: clamp(2rem, 5vw, 3.2rem); font-weight: 900;
  letter-spacing: -0.03em; line-height: 1.15;
  margin-bottom: 0.75rem;
  animation: heroFadeUp 0.6s var(--ease) 0.3s both;
}
.hero-title .accent {
  background: linear-gradient(135deg, var(--accent), var(--green));
  -webkit-background-clip: text; background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-subtitle {
  font-size: 1.05rem; color: var(--text-2); max-width: 600px;
  margin: 0 auto 2rem; line-height: 1.6;
  animation: heroFadeUp 0.6s var(--ease) 0.4s both;
}

.hero-stats {
  display: flex; justify-content: center; gap: 2.5rem;
  animation: heroFadeUp 0.6s var(--ease) 0.5s both;
}
.hero-stat {
  text-align: center;
}
.hero-stat-num {
  display: block; font-size: 1.5rem; font-weight: 800;
  background: linear-gradient(135deg, var(--text), var(--accent));
  -webkit-background-clip: text; background-clip: text;
  -webkit-text-fill-color: transparent;
}
.hero-stat-label {
  font-size: 0.72rem; color: var(--text-3); text-transform: uppercase;
  letter-spacing: 0.08em; font-weight: 500;
}

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

/* ═══ ACHIEVEMENT BADGES ═══ */
.hero-achievements {
  display: flex; justify-content: center; gap: 0.75rem;
  margin-top: 2rem; animation: heroFadeUp 0.6s var(--ease) 0.6s both;
}
.achievement-badge {
  display: flex; align-items: center; gap: 0.4rem;
  padding: 0.35rem 0.75rem; border-radius: 100px;
  font-family: var(--font-mono); font-size: 0.62rem; font-weight: 600;
  border: 1px solid; letter-spacing: 0.03em;
  transition: all 0.3s var(--ease);
}
.achievement-badge:hover { transform: translateY(-2px); }
.achievement-badge.bronze {
  background: rgba(205,127,50,0.1); border-color: rgba(205,127,50,0.25); color: #cd7f32;
}
.achievement-badge.silver {
  background: rgba(192,192,192,0.1); border-color: rgba(192,192,192,0.25); color: #c0c0c0;
}
.achievement-badge.gold {
  background: rgba(255,215,0,0.1); border-color: rgba(255,215,0,0.25); color: #ffd600;
}
.achievement-badge.locked {
  background: rgba(255,255,255,0.03); border-color: var(--border); color: var(--text-3);
  opacity: 0.5;
}

/* ═══ STICKY NAV ═══ */
.course-nav {
  position: sticky; top: 0; z-index: 100;
  display: flex; align-items: center; gap: 1rem;
  padding: 0.75rem 2rem;
  background: var(--bg-glass);
  backdrop-filter: blur(20px) saturate(1.3);
  -webkit-backdrop-filter: blur(20px) saturate(1.3);
  border-bottom: 1px solid var(--border);
  transition: box-shadow 0.3s;
}
.course-nav.scrolled { box-shadow: 0 4px 30px rgba(0,0,0,0.3); }

.nav-back {
  font-family: var(--font-mono); font-size: 0.72rem; font-weight: 500;
  color: var(--text-2); text-decoration: none;
  padding: 0.35rem 0.75rem; border-radius: var(--radius-xs);
  border: 1px solid var(--border);
  transition: all 0.25s var(--ease);
  white-space: nowrap;
}
.nav-back:hover { color: var(--accent); border-color: rgba(108,99,255,0.3); background: var(--accent-dim); }

.nav-title {
  font-weight: 700; font-size: 0.85rem; color: var(--text);
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
  flex-shrink: 0;
}

.nav-progress {
  display: flex; align-items: center; gap: 0.6rem;
  margin-left: auto; flex-shrink: 0;
}
.nav-bar {
  width: 120px; height: 4px; border-radius: 2px;
  background: var(--bg-4); overflow: hidden;
}
.nav-fill {
  height: 100%; border-radius: 2px; width: 0%;
  background: linear-gradient(90deg, var(--accent), var(--green));
  transition: width 0.5s var(--ease);
}
.nav-pct {
  font-family: var(--font-mono); font-size: 0.68rem; font-weight: 600;
  color: var(--accent); min-width: 32px; text-align: right;
}

/* ═══ CONTENT AREA ═══ */
.course-content {
  max-width: 860px; margin: 0 auto;
  padding: 2rem 1.5rem 4rem;
}

/* ═══ SECTION HEADER ═══ */
.section-header {
  display: flex; align-items: center; gap: 0.75rem;
  margin: 2.5rem 0 1.25rem; padding-bottom: 0.75rem;
  border-bottom: 1px solid var(--border);
}
.section-header-dot {
  width: 8px; height: 8px; border-radius: 50%;
  background: var(--accent); flex-shrink: 0;
  box-shadow: 0 0 12px var(--glow);
}
.section-header-text {
  font-family: var(--font-mono); font-size: 0.68rem; font-weight: 600;
  color: var(--accent); letter-spacing: 0.12em; text-transform: uppercase;
}
.section-header-line {
  flex: 1; height: 1px;
  background: linear-gradient(90deg, var(--border-hover), transparent);
}

/* ═══ LESSON CARD ═══ */
.lesson-card {
  position: relative;
  border-radius: var(--radius);
  background: var(--bg-2);
  border: 1px solid var(--border);
  margin-bottom: 0.6rem;
  overflow: hidden;
  transition: all 0.3s var(--ease);
}
.lesson-card::before {
  content: ''; position: absolute; left: 0; top: 0; bottom: 0; width: 3px;
  background: linear-gradient(180deg, var(--accent), transparent);
  opacity: 0; transition: opacity 0.3s;
}
.lesson-card:hover {
  border-color: var(--border-hover);
  transform: translateY(-1px);
  box-shadow: 0 4px 20px rgba(0,0,0,0.2);
}
.lesson-card.active {
  border-color: rgba(108,99,255,0.25);
  background: var(--bg-3);
  box-shadow: 0 8px 32px rgba(0,0,0,0.25), 0 0 0 1px rgba(108,99,255,0.08);
}
.lesson-card.active::before { opacity: 1; }
.lesson-card.completed { border-color: rgba(0,230,118,0.15); }
.lesson-card.completed::before { background: linear-gradient(180deg, var(--green), transparent); opacity: 1; }

/* ── Header (clickable) ── */
.lesson-header {
  display: flex; align-items: center; gap: 1rem;
  width: 100%; padding: 1rem 1.25rem;
  background: none; border: none; color: var(--text);
  font-family: var(--font-body); font-size: 1rem; text-align: left;
  cursor: pointer; outline: none;
  transition: background 0.2s;
}
.lesson-header:hover { background: rgba(255,255,255,0.02); }

.lesson-num {
  display: flex; align-items: center; justify-content: center;
  width: 36px; height: 36px; border-radius: 10px; flex-shrink: 0;
  background: var(--accent-dim); border: 1px solid rgba(108,99,255,0.12);
  font-family: var(--font-mono); font-size: 0.75rem; font-weight: 700;
  color: var(--accent);
  transition: all 0.3s var(--ease);
}
.lesson-card.active .lesson-num {
  background: var(--accent); color: #fff;
  box-shadow: 0 4px 16px rgba(108,99,255,0.3);
}
.lesson-card.completed .lesson-num {
  background: var(--green); color: #000; border-color: var(--green);
}

.lesson-info { flex: 1; min-width: 0; }
.lesson-info h3 {
  font-size: 0.92rem; font-weight: 700; margin-bottom: 0.15rem;
  transition: color 0.2s;
}
.lesson-card.active .lesson-info h3 { color: #fff; }
.lesson-info p {
  font-size: 0.76rem; color: var(--text-2); line-height: 1.4;
  display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden;
}

/* Lesson meta row */
.lesson-meta {
  display: flex; align-items: center; gap: 0.75rem; margin-top: 0.35rem;
}
.lesson-meta-item {
  display: flex; align-items: center; gap: 0.25rem;
  font-family: var(--font-mono); font-size: 0.6rem; color: var(--text-3);
}
.lesson-meta-item svg { width: 12px; height: 12px; opacity: 0.6; }
.lesson-difficulty {
  font-family: var(--font-mono); font-size: 0.55rem; font-weight: 600;
  padding: 0.15rem 0.45rem; border-radius: 100px;
  text-transform: uppercase; letter-spacing: 0.05em;
}
.lesson-difficulty.easy { background: var(--green-dim); color: var(--green); }
.lesson-difficulty.medium { background: var(--orange-dim); color: var(--orange); }
.lesson-difficulty.hard { background: var(--red-dim); color: var(--red); }

.lesson-chevron {
  width: 20px; height: 20px; flex-shrink: 0;
  color: var(--text-3); transition: transform 0.3s var(--ease);
}
.lesson-card.active .lesson-chevron { transform: rotate(180deg); color: var(--accent); }

.lesson-status {
  font-family: var(--font-mono); font-size: 0.6rem; font-weight: 600;
  padding: 0.2rem 0.5rem; border-radius: 100px; flex-shrink: 0;
  letter-spacing: 0.05em;
}
.lesson-status.done { background: var(--green-dim); color: var(--green); }
.lesson-status.current { background: var(--accent-dim); color: var(--accent); }

/* ── Content (expandable) ── */
.lesson-body {
  max-height: 0; overflow: hidden;
  transition: max-height 0.5s var(--ease), padding 0.3s;
}
.lesson-card.active .lesson-body {
  max-height: 5000px;
  padding: 0 1.5rem 1.5rem;
}

.lesson-body h4 {
  font-size: 0.95rem; font-weight: 700; color: var(--text);
  margin: 1.5rem 0 0.75rem; padding-bottom: 0.4rem;
  border-bottom: 1px solid var(--border);
}
.lesson-body h4:first-child { margin-top: 0.5rem; }

.lesson-body p {
  font-size: 0.88rem; color: var(--text-2); line-height: 1.7;
  margin-bottom: 0.75rem;
}

.lesson-body ul, .lesson-body ol {
  padding-left: 1.25rem; margin-bottom: 0.75rem;
}
.lesson-body li {
  font-size: 0.85rem; color: var(--text-2); line-height: 1.7;
  margin-bottom: 0.3rem;
}
.lesson-body li::marker { color: var(--accent); }

.lesson-body a {
  color: var(--accent); text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color 0.2s;
}
.lesson-body a:hover { border-bottom-color: var(--accent); }

.lesson-body strong { color: var(--text); font-weight: 600; }

/* ═══ CODE BLOCKS ═══ */
.code-block {
  position: relative; margin: 1rem 0; border-radius: var(--radius-sm);
  background: #0d1117; border: 1px solid rgba(255,255,255,0.06);
  overflow: hidden;
}
.code-block::before {
  content: ''; position: absolute; top: 0; left: 0; right: 0; height: 2px;
  background: linear-gradient(90deg, var(--accent), var(--green), var(--cyan));
  opacity: 0.6;
}
.code-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 0.5rem 1rem;
  background: rgba(255,255,255,0.03); border-bottom: 1px solid rgba(255,255,255,0.06);
}
.code-lang {
  font-family: var(--font-mono); font-size: 0.62rem; font-weight: 600;
  color: var(--text-3); text-transform: uppercase; letter-spacing: 0.08em;
}
.code-copy {
  display: flex; align-items: center; gap: 0.35rem;
  padding: 0.25rem 0.6rem; border-radius: var(--radius-xs);
  background: rgba(255,255,255,0.06); border: none;
  color: var(--text-3); font-family: var(--font-mono); font-size: 0.62rem;
  cursor: pointer; transition: all 0.2s;
}
.code-copy:hover { background: rgba(255,255,255,0.1); color: var(--text); }
.code-copy.copied { color: var(--green); }

.code-block pre {
  margin: 0; padding: 1rem 1.25rem;
  overflow-x: auto;
  font-family: var(--font-mono); font-size: 0.82rem;
  line-height: 1.65; color: #e6edf3;
  scrollbar-width: thin; scrollbar-color: rgba(255,255,255,0.1) transparent;
}
.code-block pre::-webkit-scrollbar { height: 4px; }
.code-block pre::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.1); border-radius: 2px; }

/* Inline code */
.lesson-body code, .lesson-body p code {
  font-family: var(--font-mono); font-size: 0.82em;
  background: var(--accent-dim); color: var(--accent);
  padding: 0.15em 0.4em; border-radius: 4px;
  border: 1px solid rgba(108,99,255,0.12);
}

/* ═══ CALLOUTS ═══ */
.callout {
  display: flex; gap: 0.75rem; padding: 1rem 1.25rem;
  border-radius: var(--radius-sm); margin: 1rem 0;
  border: 1px solid; font-size: 0.85rem; line-height: 1.6;
  animation: calloutIn 0.4s var(--ease);
}
@keyframes calloutIn { from { opacity: 0; transform: translateX(-10px); } }

.callout-icon { font-size: 1.1rem; flex-shrink: 0; margin-top: 0.1rem; }
.callout-body { flex: 1; }
.callout-body strong { display: block; margin-bottom: 0.2rem; font-size: 0.82rem; }

.callout.note {
  background: var(--accent-dim); border-color: rgba(108,99,255,0.15);
  color: var(--text-2);
}
.callout.note .callout-icon { color: var(--accent); }
.callout.note strong { color: var(--accent); }

.callout.warning {
  background: var(--orange-dim); border-color: rgba(255,152,0,0.15);
  color: var(--text-2);
}
.callout.warning .callout-icon { color: var(--orange); }
.callout.warning strong { color: var(--orange); }

.callout.danger {
  background: var(--red-dim); border-color: rgba(255,82,82,0.15);
  color: var(--text-2);
}
.callout.danger .callout-icon { color: var(--red); }
.callout.danger strong { color: var(--red); }

.callout.tip {
  background: var(--green-dim); border-color: rgba(0,230,118,0.15);
  color: var(--text-2);
}
.callout.tip .callout-icon { color: var(--green); }
.callout.tip strong { color: var(--green); }

.callout.info {
  background: var(--cyan-dim); border-color: rgba(0,188,212,0.15);
  color: var(--text-2);
}
.callout.info .callout-icon { color: var(--cyan); }
.callout.info strong { color: var(--cyan); }

/* ═══ TABS ═══ */
.lesson-tabs {
  display: flex; gap: 2px; margin: 1rem 0 0;
  background: var(--bg-4); border-radius: var(--radius-sm) var(--radius-sm) 0 0;
  padding: 3px 3px 0;
  overflow-x: auto;
}
.lesson-tab {
  padding: 0.5rem 1rem; border-radius: var(--radius-xs) var(--radius-xs) 0 0;
  background: transparent; border: none;
  font-family: var(--font-body); font-size: 0.78rem; font-weight: 500;
  color: var(--text-3); cursor: pointer;
  transition: all 0.2s; white-space: nowrap;
}
.lesson-tab:hover { color: var(--text-2); background: rgba(255,255,255,0.03); }
.lesson-tab.active {
  background: #0d1117; color: var(--accent); font-weight: 600;
}

.lesson-tab-panel {
  display: none; background: #0d1117;
  border: 1px solid var(--border); border-top: none;
  border-radius: 0 0 var(--radius-sm) var(--radius-sm);
  padding: 1rem 1.25rem;
}
.lesson-tab-panel.active { display: block; }
.lesson-tab-panel pre { margin: 0; }
.lesson-tab-panel code { font-size: 0.82rem; }

/* ═══ QUIZ ═══ */
.quiz {
  background: var(--bg-3); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1.5rem;
  margin: 1.5rem 0;
}
.quiz-header {
  display: flex; align-items: center; gap: 0.6rem;
  margin-bottom: 1rem;
}
.quiz-header-icon { font-size: 1.2rem; }
.quiz-header-text {
  font-family: var(--font-mono); font-size: 0.7rem; font-weight: 600;
  color: var(--accent); letter-spacing: 0.08em; text-transform: uppercase;
}
.quiz-question {
  font-size: 0.95rem; font-weight: 600; color: var(--text);
  margin-bottom: 1rem; line-height: 1.5;
}
.quiz-options { display: flex; flex-direction: column; gap: 0.5rem; }
.quiz-option {
  display: flex; align-items: center; gap: 0.75rem;
  padding: 0.75rem 1rem; border-radius: var(--radius-sm);
  background: var(--bg-2); border: 1px solid var(--border);
  cursor: pointer; transition: all 0.25s var(--ease);
  font-size: 0.85rem; color: var(--text-2);
}
.quiz-option:hover {
  border-color: rgba(108,99,255,0.3); background: var(--accent-dim);
}
.quiz-option input { display: none; }
.quiz-radio {
  width: 18px; height: 18px; border-radius: 50%; flex-shrink: 0;
  border: 2px solid var(--text-3); transition: all 0.25s;
  display: flex; align-items: center; justify-content: center;
}
.quiz-option.selected .quiz-radio {
  border-color: var(--accent); background: var(--accent);
}
.quiz-option.selected .quiz-radio::after {
  content: ''; width: 6px; height: 6px; border-radius: 50%; background: #fff;
}
.quiz-option.correct {
  border-color: var(--green); background: var(--green-dim); color: var(--green);
}
.quiz-option.correct .quiz-radio { border-color: var(--green); background: var(--green); }
.quiz-option.wrong {
  border-color: var(--red); background: var(--red-dim); color: var(--red);
}
.quiz-option.wrong .quiz-radio { border-color: var(--red); background: var(--red); }

.quiz-feedback {
  margin-top: 0.75rem; padding: 0.75rem 1rem;
  border-radius: var(--radius-xs); font-size: 0.82rem;
  display: none;
}
.quiz-feedback.show { display: block; animation: calloutIn 0.3s var(--ease); }
.quiz-feedback.correct { background: var(--green-dim); color: var(--green); border: 1px solid rgba(0,230,118,0.15); }
.quiz-feedback.wrong { background: var(--red-dim); color: var(--red); border: 1px solid rgba(255,82,82,0.15); }

.quiz-nav {
  display: flex; justify-content: space-between; align-items: center;
  margin-top: 1rem; padding-top: 0.75rem; border-top: 1px solid var(--border);
}
.quiz-counter {
  font-family: var(--font-mono); font-size: 0.7rem; color: var(--text-3);
}
.quiz-score {
  font-family: var(--font-mono); font-size: 0.75rem; font-weight: 700;
  color: var(--green);
}

/* ═══ BOOKMARK ═══ */
.bookmark-btn {
  position: absolute; top: 1rem; right: 1rem;
  width: 32px; height: 32px; border-radius: 50%;
  background: rgba(255,255,255,0.05); border: 1px solid var(--border);
  color: var(--text-3); cursor: pointer;
  display: flex; align-items: center; justify-content: center;
  font-size: 0.85rem; transition: all 0.3s var(--ease-bounce);
  z-index: 5;
}
.bookmark-btn:hover { transform: scale(1.15); background: rgba(255,255,255,0.08); }
.bookmark-btn.bookmarked {
  color: var(--orange); background: var(--orange-dim);
  border-color: rgba(255,152,0,0.3);
  animation: bookmarkPop 0.4s var(--ease-bounce);
}
@keyframes bookmarkPop { 0%{transform:scale(1)} 50%{transform:scale(1.3)} 100%{transform:scale(1)} }

/* ═══ PREV / NEXT ═══ */
.lesson-nav {
  display: flex; gap: 1rem; margin-top: 2rem;
}
.lesson-nav-btn {
  flex: 1; display: flex; flex-direction: column; gap: 0.25rem;
  padding: 1rem 1.25rem; border-radius: var(--radius-sm);
  background: var(--bg-2); border: 1px solid var(--border);
  text-decoration: none; color: var(--text);
  transition: all 0.3s var(--ease); cursor: pointer;
}
.lesson-nav-btn:hover {
  border-color: rgba(108,99,255,0.3); transform: translateY(-2px);
  box-shadow: 0 4px 16px rgba(0,0,0,0.2);
}
.lesson-nav-btn.next { text-align: right; margin-left: auto; }
.lesson-nav-label {
  font-family: var(--font-mono); font-size: 0.6rem; font-weight: 600;
  color: var(--text-3); text-transform: uppercase; letter-spacing: 0.1em;
}
.lesson-nav-title {
  font-size: 0.85rem; font-weight: 600; color: var(--text);
}
.lesson-nav-btn:hover .lesson-nav-title { color: var(--accent); }

/* ═══ SEARCH ═══ */
.course-search {
  position: relative; margin-bottom: 1.5rem;
}
.course-search-input {
  width: 100%; padding: 0.75rem 1rem 0.75rem 2.75rem;
  background: var(--bg-2); border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-family: var(--font-body); font-size: 0.85rem; color: var(--text);
  outline: none; transition: all 0.3s var(--ease);
}
.course-search-input:focus {
  border-color: rgba(108,99,255,0.3);
  box-shadow: 0 0 0 3px rgba(108,99,255,0.08);
}
.course-search-input::placeholder { color: var(--text-3); }
.course-search-icon {
  position: absolute; left: 0.9rem; top: 50%; transform: translateY(-50%);
  color: var(--text-3); font-size: 0.85rem; pointer-events: none;
}
.course-search-count {
  position: absolute; right: 0.9rem; top: 50%; transform: translateY(-50%);
  font-family: var(--font-mono); font-size: 0.62rem; color: var(--text-3);
}

/* ═══ RESOURCES ═══ */
.resources-section {
  margin-top: 3rem; padding-top: 2rem;
  border-top: 1px solid var(--border);
}
.resources-title {
  font-size: 1.1rem; font-weight: 700; margin-bottom: 1.25rem;
  display: flex; align-items: center; gap: 0.5rem;
}
.resources-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
  gap: 0.75rem;
}
.resource-card {
  padding: 1rem; border-radius: var(--radius-sm);
  background: var(--bg-2); border: 1px solid var(--border);
  transition: all 0.3s var(--ease);
}
.resource-card:hover {
  border-color: var(--border-hover); transform: translateY(-2px);
  box-shadow: 0 4px 16px rgba(0,0,0,0.2);
}
.resource-card-icon { font-size: 1.5rem; margin-bottom: 0.5rem; }
.resource-card-title {
  font-size: 0.85rem; font-weight: 600; color: var(--text);
  margin-bottom: 0.25rem;
}
.resource-card-desc {
  font-size: 0.75rem; color: var(--text-2); line-height: 1.5;
  margin-bottom: 0.5rem;
}
.resource-card-link {
  font-family: var(--font-mono); font-size: 0.68rem; font-weight: 500;
  color: var(--accent); text-decoration: none;
  display: inline-flex; align-items: center; gap: 0.3rem;
  transition: gap 0.2s;
}
.resource-card-link:hover { gap: 0.5rem; }

/* ═══ AI CHAT ═══ */
.course-ai {
  margin-top: 3rem; padding: 1.5rem;
  border-radius: var(--radius);
  background: var(--bg-2); border: 1px solid var(--border);
}
.course-ai-header {
  display: flex; align-items: center; gap: 0.75rem;
  margin-bottom: 1rem; padding-bottom: 0.75rem;
  border-bottom: 1px solid var(--border);
}
.course-ai-avatar {
  width: 36px; height: 36px; border-radius: 10px;
  background: linear-gradient(135deg, var(--accent), var(--green));
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-mono); font-size: 0.7rem; font-weight: 700;
  color: #fff;
}
.course-ai-name { font-size: 0.88rem; font-weight: 600; }
.course-ai-model {
  font-family: var(--font-mono); font-size: 0.62rem; color: var(--text-3);
}

.course-ai-messages {
  height: 350px; overflow-y: auto; padding: 0.5rem 0;
  display: flex; flex-direction: column; gap: 0.75rem;
  scrollbar-width: thin; scrollbar-color: rgba(108,99,255,0.2) transparent;
}
.course-ai-messages::-webkit-scrollbar { width: 3px; }
.course-ai-messages::-webkit-scrollbar-thumb { background: rgba(108,99,255,0.2); border-radius: 2px; }

.course-ai-msg {
  padding: 0.75rem 1rem; border-radius: var(--radius-sm);
  font-size: 0.85rem; line-height: 1.6; max-width: 85%;
  animation: msgIn 0.3s var(--ease);
}
@keyframes msgIn { from { opacity: 0; transform: translateY(8px); } }

.course-ai-msg.user {
  align-self: flex-end;
  background: var(--accent); color: #fff;
  border-bottom-right-radius: 4px;
}
.course-ai-msg.bot {
  align-self: flex-start;
  background: var(--bg-3); color: var(--text-2);
  border-bottom-left-radius: 4px;
}
.course-ai-msg.bot pre {
  background: #0d1117; padding: 0.75rem; border-radius: var(--radius-xs);
  overflow-x: auto; margin: 0.5rem 0;
  font-family: var(--font-mono); font-size: 0.78rem; line-height: 1.5;
}
.course-ai-msg.bot code {
  font-family: var(--font-mono); font-size: 0.82em;
  background: var(--accent-dim); padding: 0.1em 0.3em; border-radius: 3px;
}
.course-ai-msg.bot pre code { background: none; padding: 0; }

.course-ai-input-area {
  display: flex; gap: 0.5rem; margin-top: 0.75rem;
}
.course-ai-input {
  flex: 1; padding: 0.7rem 1rem;
  background: var(--bg-3); border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  font-family: var(--font-body); font-size: 0.85rem; color: var(--text);
  outline: none; transition: border-color 0.2s;
}
.course-ai-input:focus { border-color: rgba(108,99,255,0.3); }
.course-ai-send {
  padding: 0.7rem 1.25rem; border-radius: var(--radius-sm);
  background: var(--accent); border: none;
  font-family: var(--font-body); font-size: 0.82rem; font-weight: 600;
  color: #fff; cursor: pointer; transition: all 0.2s;
  white-space: nowrap;
}
.course-ai-send:hover { background: #5a52e0; transform: translateY(-1px); }

.course-ai-typing {
  display: flex; gap: 4px; padding: 0.5rem 0.75rem;
}
.course-ai-typing span {
  width: 6px; height: 6px; border-radius: 50%; background: var(--text-3);
  animation: typingBounce 1.4s ease-in-out infinite;
}
.course-ai-typing span:nth-child(2) { animation-delay: 0.15s; }
.course-ai-typing span:nth-child(3) { animation-delay: 0.3s; }
@keyframes typingBounce { 0%,60%,100%{transform:translateY(0)} 30%{transform:translateY(-6px)} }

/* ═══ PROGRESS COUNTER ═══ */
.progress-counter {
  display: flex; align-items: center; gap: 1rem;
  padding: 1rem 1.25rem; margin-bottom: 1.5rem;
  border-radius: var(--radius-sm);
  background: var(--bg-2); border: 1px solid var(--border);
}
.progress-counter-ring {
  width: 48px; height: 48px; position: relative; flex-shrink: 0;
}
.progress-counter-ring svg { width: 100%; height: 100%; transform: rotate(-90deg); }
.progress-counter-ring circle {
  fill: none; stroke-width: 4; stroke-linecap: round;
}
.progress-counter-bg { stroke: var(--bg-4); }
.progress-counter-fill {
  stroke: var(--accent);
  stroke-dasharray: 138.2;
  stroke-dashoffset: 138.2;
  transition: stroke-dashoffset 0.8s var(--ease);
}
.progress-counter-pct {
  position: absolute; inset: 0;
  display: flex; align-items: center; justify-content: center;
  font-family: var(--font-mono); font-size: 0.72rem; font-weight: 700;
  color: var(--accent);
}
.progress-counter-text {
  font-size: 0.82rem; color: var(--text-2);
}
.progress-counter-text strong {
  color: var(--text); font-weight: 600;
}

/* ═══ COMPLETION MODAL ═══ */
.completion-overlay {
  position: fixed; inset: 0; z-index: 9999;
  background: rgba(5,5,8,0.92); backdrop-filter: blur(12px);
  display: flex; align-items: center; justify-content: center;
  opacity: 0; pointer-events: none;
  transition: opacity 0.4s var(--ease);
}
.completion-overlay.show { opacity: 1; pointer-events: all; }

.completion-modal {
  text-align: center; padding: 3rem 2.5rem;
  background: var(--bg-2); border: 1px solid rgba(0,230,118,0.2);
  border-radius: var(--radius); max-width: 420px; width: 90%;
  transform: scale(0.9) translateY(20px);
  transition: transform 0.5s var(--ease-bounce);
  box-shadow: 0 24px 80px rgba(0,230,118,0.15);
}
.completion-overlay.show .completion-modal { transform: scale(1) translateY(0); }

.completion-icon { font-size: 4rem; margin-bottom: 1rem; }
.completion-title {
  font-size: 1.5rem; font-weight: 800; margin-bottom: 0.5rem;
  background: linear-gradient(135deg, var(--green), var(--cyan));
  -webkit-background-clip: text; background-clip: text;
  -webkit-text-fill-color: transparent;
}
.completion-text {
  font-size: 0.9rem; color: var(--text-2); margin-bottom: 1.5rem; line-height: 1.6;
}
.completion-stats {
  display: flex; justify-content: center; gap: 2rem; margin-bottom: 1.5rem;
}
.completion-stat-num {
  font-family: var(--font-mono); font-size: 1.8rem; font-weight: 800;
  color: var(--green); display: block;
}
.completion-stat-label {
  font-size: 0.65rem; color: var(--text-3); text-transform: uppercase;
  letter-spacing: 0.08em;
}
.completion-close {
  padding: 0.65rem 2rem; border-radius: var(--radius-sm);
  background: var(--green); border: none;
  font-family: var(--font-body); font-size: 0.85rem; font-weight: 700;
  color: #000; cursor: pointer; transition: all 0.2s;
}
.completion-close:hover { transform: translateY(-2px); box-shadow: 0 4px 20px rgba(0,230,118,0.3); }

/* ═══ FOOTER ═══ */
.course-footer {
  padding: 2rem 1.5rem; text-align: center;
  border-top: 1px solid var(--border);
}
.course-footer-text {
  font-size: 0.78rem; color: var(--text-3); margin-bottom: 1rem;
}

/* ═══ KEYBOARD HINT ═══ */
.kbd-hints {
  display: flex; gap: 0.75rem; flex-wrap: wrap;
  margin-bottom: 1rem; padding: 0.75rem 1rem;
  background: var(--bg-2); border-radius: var(--radius-sm);
  border: 1px solid var(--border);
}
.kbd-hint {
  display: flex; align-items: center; gap: 0.4rem;
  font-size: 0.7rem; color: var(--text-3);
}
.kbd {
  display: inline-flex; align-items: center; justify-content: center;
  min-width: 22px; height: 20px; padding: 0 5px;
  background: var(--bg-4); border: 1px solid var(--border-hover);
  border-radius: 4px;
  font-family: var(--font-mono); font-size: 0.6rem; font-weight: 600;
  color: var(--text-2);
}

/* ═══ TOAST NOTIFICATION ═══ */
.toast {
  position: fixed; bottom: 2rem; left: 50%; transform: translateX(-50%) translateY(100px);
  padding: 0.6rem 1.25rem; border-radius: var(--radius-sm);
  background: var(--bg-3); border: 1px solid var(--border);
  font-family: var(--font-mono); font-size: 0.72rem; color: var(--text);
  z-index: 10000; opacity: 0;
  transition: all 0.4s var(--ease);
  box-shadow: 0 8px 32px rgba(0,0,0,0.3);
}
.toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }
.toast.success { border-color: rgba(0,230,118,0.3); color: var(--green); }

/* ═══ RESPONSIVE ═══ */
@media (max-width: 768px) {
  .course-hero { padding: 4rem 1.25rem 3rem; }
  .hero-stats { gap: 1.5rem; }
  .hero-achievements { flex-wrap: wrap; }
  .course-nav { padding: 0.6rem 1rem; gap: 0.5rem; }
  .nav-title { display: none; }
  .nav-bar { width: 60px; }
  .course-content { padding: 1.5rem 1rem 3rem; }
  .lesson-header { padding: 0.85rem 1rem; gap: 0.75rem; }
  .lesson-meta { display: none; }
  .lesson-body { padding: 0 1rem 1rem !important; }
  .lesson-nav { flex-direction: column; }
  .resources-grid { grid-template-columns: 1fr; }
  .kbd-hints { display: none; }
  .course-ai-messages { height: 250px; }
}

@media (max-width: 480px) {
  .hero-title { font-size: 1.6rem; }
  .hero-subtitle { font-size: 0.9rem; }
  .hero-stats { flex-wrap: wrap; gap: 1rem; }
}

/* ═══ PREMIUM ANIMATIONS ═══ */

/* Lesson card hover float */
.lesson-header:hover {
  transform: translateY(-1px);
  box-shadow: 0 4px 20px rgba(108,99,255,0.08);
}
.lesson-header:active {
  transform: translateY(0);
}

/* Code block glow on hover */
pre:hover {
  box-shadow: 0 0 20px rgba(108,99,255,0.08), inset 0 0 0 1px rgba(108,99,255,0.12);
}

/* Shimmer effect for progress bar */
.progress-bar-fill {
  position: relative;
  overflow: hidden;
}
.progress-bar-fill::after {
  content: ''; position: absolute; top: 0; left: -100%; width: 100%; height: 100%;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.15), transparent);
  animation: shimmer 2s infinite;
}
@keyframes shimmer {
  0% { left: -100%; }
  100% { left: 100%; }
}

/* Callout slide-in */
.callout {
  animation: calloutSlide 0.4s var(--ease);
}
@keyframes calloutSlide {
  from { opacity: 0; transform: translateX(-12px); }
  to { opacity: 1; transform: translateX(0); }
}

/* Quiz option pulse on hover */
.quiz-option:hover {
  transform: translateX(4px);
  box-shadow: 0 2px 12px rgba(108,99,255,0.1);
}

/* Bookmark pop */
.bookmark-btn:hover {
  transform: scale(1.15);
}
.bookmark-btn.active {
  animation: bookmarkBounce 0.4s var(--ease-bounce);
}
@keyframes bookmarkBounce {
  0% { transform: scale(1); }
  40% { transform: scale(1.35); }
  100% { transform: scale(1); }
}

/* Resource card hover */
.resource-card:hover {
  transform: translateY(-3px) scale(1.01);
  box-shadow: 0 8px 30px rgba(108,99,255,0.12);
}
.resource-card:hover .resource-icon {
  transform: scale(1.1) rotate(-3deg);
}

/* Nav button ripple */
.lesson-nav-btn::after {
  content: ''; position: absolute; inset: 0; border-radius: inherit;
  background: radial-gradient(circle at center, rgba(108,99,255,0.15), transparent 70%);
  opacity: 0; transition: opacity 0.3s;
}
.lesson-nav-btn:hover::after { opacity: 1; }

/* AI message entrance */
.ai-msg {
  animation: aiMsgIn 0.35s var(--ease);
}
@keyframes aiMsgIn {
  from { opacity: 0; transform: translateY(10px) scale(0.98); }
  to { opacity: 1; transform: translateY(0) scale(1); }
}

/* Typing indicator bounce */
.typing-indicator span:nth-child(1) { animation-delay: 0s; }
.typing-indicator span:nth-child(2) { animation-delay: 0.15s; }
.typing-indicator span:nth-child(3) { animation-delay: 0.3s; }

/* Copy button success flash */
.copy-btn.copied {
  background: var(--green) !important;
  color: #000 !important;
}

/* Scroll reveal for lesson bodies */
.lesson-body {
  animation: lessonReveal 0.4s var(--ease);
}
@keyframes lessonReveal {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Hero gradient orb animation */
.hero-bg-orb {
  animation: orbFloat 8s ease-in-out infinite;
}
@keyframes orbFloat {
  0%, 100% { transform: translate(0, 0) scale(1); }
  33% { transform: translate(30px, -20px) scale(1.05); }
  66% { transform: translate(-20px, 15px) scale(0.95); }
}

/* Smooth section transitions */
.course-content section {
  animation: sectionIn 0.5s var(--ease);
}
@keyframes sectionIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

/* ═══ HTB-STYLE PROGRESS RING ═══ */
.htb-ring {
  position: relative; display: inline-flex; align-items: center; justify-content: center;
}
.htb-ring svg { transform: rotate(-90deg); }
.htb-ring circle { fill: none; stroke-linecap: round; }
.htb-ring-bg { stroke: var(--bg-4); }
.htb-ring-fill {
  stroke: var(--green);
  transition: stroke-dashoffset 0.8s var(--ease);
}
.htb-ring-pct {
  position: absolute;
  font-family: var(--font-mono); font-size: 0.7rem; font-weight: 700;
  color: var(--green);
}

/* ═══ DIFFICULTY BADGE (global) ═══ */
.difficulty-badge {
  display: inline-flex; align-items: center; gap: 0.3rem;
  font-family: var(--font-mono); font-size: 0.58rem; font-weight: 700;
  padding: 0.2rem 0.6rem; border-radius: 100px;
  text-transform: uppercase; letter-spacing: 0.06em;
}
.difficulty-badge.easy { background: var(--green-dim); color: var(--green); border: 1px solid rgba(0,230,118,0.2); }
.difficulty-badge.medium { background: var(--orange-dim); color: var(--orange); border: 1px solid rgba(255,152,0,0.2); }
.difficulty-badge.hard { background: var(--red-dim); color: var(--red); border: 1px solid rgba(255,82,82,0.2); }

/* ═══ LESSON COMPLETION CHECKMARK ═══ */
.lesson-check {
  width: 22px; height: 22px; border-radius: 50%; flex-shrink: 0;
  border: 2px solid var(--text-3); display: flex; align-items: center; justify-content: center;
  transition: all 0.3s var(--ease);
}
.lesson-check.done {
  background: var(--green); border-color: var(--green);
  box-shadow: 0 0 12px rgba(0,230,118,0.3);
}
.lesson-check.done::after {
  content: '✓'; font-size: 0.65rem; color: #000; font-weight: 800;
}

/* ═══ HTB CHALLENGE CARD STYLE ═══ */
.challenge-card {
  position: relative;
  border-radius: var(--radius);
  background: var(--bg-2);
  border: 1px solid var(--border);
  overflow: hidden;
  transition: all 0.3s var(--ease);
}
.challenge-card::before {
  content: ''; position: absolute; top: 0; left: 0; right: 0; height: 3px;
  background: linear-gradient(90deg, var(--accent), var(--green));
  opacity: 0; transition: opacity 0.3s;
}
.challenge-card:hover::before { opacity: 1; }
.challenge-card:hover {
  border-color: var(--border-hover);
  transform: translateY(-2px);
  box-shadow: 0 8px 32px rgba(0,0,0,0.25);
}

.challenge-header {
  display: flex; align-items: center; gap: 1rem; padding: 1.25rem 1.5rem;
}
.challenge-icon {
  width: 48px; height: 48px; border-radius: 12px;
  background: var(--accent-dim); border: 1px solid rgba(108,99,255,0.12);
  display: flex; align-items: center; justify-content: center;
  font-size: 1.3rem; flex-shrink: 0;
}
.challenge-title {
  font-size: 1rem; font-weight: 700; color: var(--text);
}
.challenge-subtitle {
  font-size: 0.78rem; color: var(--text-2); margin-top: 0.15rem;
}
.challenge-meta {
  display: flex; align-items: center; gap: 1rem; padding: 0 1.5rem 1.25rem;
}
.challenge-meta-item {
  display: flex; align-items: center; gap: 0.35rem;
  font-family: var(--font-mono); font-size: 0.68rem; color: var(--text-3);
}
.challenge-meta-item svg { width: 14px; height: 14px; opacity: 0.6; }

/* ═══ ANIMATED COUNTER ═══ */
.animated-counter {
  display: inline-block;
  transition: all 0.3s var(--ease);
}
.animated-counter.counting {
  animation: counterPulse 0.3s ease;
}
@keyframes counterPulse {
  0% { transform: scale(1); }
  50% { transform: scale(1.15); color: var(--green); }
  100% { transform: scale(1); }
}