/* ================================================
   Python Learning Platform — Main Stylesheet
   Design: Dark Glassmorphism + Neon Accents
   ================================================ */

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

/* ── CSS Variables ── */
:root {
  --bg-primary: #080b14;
  --bg-secondary: #0d1120;
  --bg-card: rgba(255,255,255,0.04);
  --bg-card-hover: rgba(255,255,255,0.07);
  --glass: rgba(255,255,255,0.05);
  --glass-border: rgba(255,255,255,0.1);

  --purple: #7c3aed;
  --purple-light: #a855f7;
  --purple-dim: rgba(124,58,237,0.15);
  --cyan: #06b6d4;
  --cyan-dim: rgba(6,182,212,0.15);
  --green: #10b981;
  --green-dim: rgba(16,185,129,0.15);
  --orange: #f59e0b;
  --red: #ef4444;

  --text-primary: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-muted: #475569;

  --radius: 12px;
  --radius-lg: 20px;
  --radius-xl: 28px;
  --shadow: 0 4px 24px rgba(0,0,0,0.4);
  --shadow-glow: 0 0 40px rgba(124,58,237,0.2);
  --transition: all 0.25s cubic-bezier(0.4,0,0.2,1);
}

/* ── Reset & Base ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  font-family: 'Inter', -apple-system, sans-serif;
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.6;
  min-height: 100vh;
  overflow-x: hidden;
}

/* ── Scrollbar ── */
::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: var(--bg-secondary); }
::-webkit-scrollbar-thumb { background: var(--purple); border-radius: 3px; }
::-webkit-scrollbar-thumb:hover { background: var(--purple-light); }

/* ── Animated Background ── */
.bg-grid {
  position: fixed; inset: 0; z-index: 0; pointer-events: none;
  background-image:
    linear-gradient(rgba(124,58,237,0.03) 1px, transparent 1px),
    linear-gradient(90deg, rgba(124,58,237,0.03) 1px, transparent 1px);
  background-size: 40px 40px;
}
.bg-orb {
  position: fixed; border-radius: 50%; filter: blur(100px);
  pointer-events: none; z-index: 0; animation: float 8s ease-in-out infinite;
}
.bg-orb-1 { width:500px;height:500px;background:rgba(124,58,237,0.12);top:-100px;left:-100px; }
.bg-orb-2 { width:400px;height:400px;background:rgba(6,182,212,0.08);bottom:-50px;right:-50px;animation-delay:-4s; }
.bg-orb-3 { width:300px;height:300px;background:rgba(16,185,129,0.06);top:50%;left:50%;transform:translate(-50%,-50%);animation-delay:-2s; }

@keyframes float {
  0%,100% { transform: translateY(0) scale(1); }
  50% { transform: translateY(-30px) scale(1.05); }
}

/* ── Navigation ── */
.navbar {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  height: 64px;
  display: flex; align-items: center; justify-content: space-between;
  padding: 0 24px;
  background: rgba(8,11,20,0.85);
  backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--glass-border);
}
.nav-logo {
  display: flex; align-items: center; gap: 10px;
  font-size: 1.2rem; font-weight: 700; color: var(--text-primary);
  text-decoration: none;
}
.nav-logo-icon {
  width: 36px; height: 36px; border-radius: 10px;
  background: linear-gradient(135deg, var(--purple), var(--cyan));
  display: flex; align-items: center; justify-content: center;
  font-size: 1.1rem;
}
.nav-links { display: flex; align-items: center; gap: 8px; }
.nav-links a {
  padding: 6px 16px; border-radius: 8px;
  color: var(--text-secondary); text-decoration: none;
  font-size: 0.9rem; font-weight: 500;
  transition: var(--transition);
}
.nav-links a:hover, .nav-links a.active {
  color: var(--text-primary); background: var(--glass);
}
.nav-btn {
  padding: 8px 20px; border-radius: 10px; border: none; cursor: pointer;
  font-size: 0.9rem; font-weight: 600; font-family: inherit;
  background: linear-gradient(135deg, var(--purple), var(--purple-light));
  color: white; transition: var(--transition);
}
.nav-btn:hover { transform: translateY(-1px); box-shadow: 0 4px 20px rgba(124,58,237,0.4); }
.nav-progress-bar {
  position: fixed; top: 64px; left: 0; height: 3px; z-index: 99;
  background: linear-gradient(90deg, var(--purple), var(--cyan));
  transition: width 0.5s ease;
}

/* ── Hero Section ── */
.hero {
  position: relative; z-index: 1;
  min-height: 100vh;
  display: flex; align-items: center; justify-content: center;
  padding: 100px 24px 60px;
  text-align: center;
}
.hero-content { max-width: 800px; }
.hero-badge {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 6px 16px; border-radius: 100px;
  background: var(--purple-dim); border: 1px solid rgba(124,58,237,0.3);
  font-size: 0.85rem; font-weight: 600; color: var(--purple-light);
  margin-bottom: 24px; animation: fadeInDown 0.6s ease;
}
.hero-badge::before { content:''; width:6px;height:6px;border-radius:50%;background:var(--purple-light);animation:pulse 2s infinite; }
@keyframes pulse { 0%,100%{opacity:1}50%{opacity:0.3} }

.hero-title {
  font-size: clamp(2.5rem, 6vw, 4.5rem);
  font-weight: 900; line-height: 1.1;
  margin-bottom: 20px;
  animation: fadeInDown 0.6s ease 0.1s both;
}
.hero-title .gradient-text {
  background: linear-gradient(135deg, var(--purple-light), var(--cyan));
  -webkit-background-clip: text; background-clip: text;
  -webkit-text-fill-color: transparent;
}
.hero-subtitle {
  font-size: 1.15rem; color: var(--text-secondary);
  max-width: 600px; margin: 0 auto 40px;
  animation: fadeInDown 0.6s ease 0.2s both;
}
.hero-actions {
  display: flex; align-items: center; justify-content: center; gap: 16px;
  flex-wrap: wrap;
  animation: fadeInDown 0.6s ease 0.3s both;
}
.btn-primary {
  padding: 14px 32px; border-radius: 12px; border: none; cursor: pointer;
  font-size: 1rem; font-weight: 700; font-family: inherit;
  background: linear-gradient(135deg, var(--purple), var(--purple-light));
  color: white; transition: var(--transition);
  display: flex; align-items: center; gap: 8px;
}
.btn-primary:hover { transform: translateY(-2px); box-shadow: 0 8px 32px rgba(124,58,237,0.5); }
.btn-secondary {
  padding: 14px 32px; border-radius: 12px; border: 1px solid var(--glass-border); cursor: pointer;
  font-size: 1rem; font-weight: 600; font-family: inherit;
  background: var(--glass); color: var(--text-primary); transition: var(--transition);
  backdrop-filter: blur(10px);
}
.btn-secondary:hover { background: var(--bg-card-hover); border-color: var(--purple); }

/* ── Stats ── */
.hero-stats {
  display: flex; justify-content: center; gap: 40px;
  margin-top: 60px; flex-wrap: wrap;
  animation: fadeInUp 0.6s ease 0.4s both;
}
.stat-item { text-align: center; }
.stat-number {
  font-size: 2rem; font-weight: 800;
  background: linear-gradient(135deg, var(--purple-light), var(--cyan));
  -webkit-background-clip: text; background-clip: text;
  -webkit-text-fill-color: transparent;
}
.stat-label { font-size: 0.8rem; color: var(--text-muted); margin-top: 2px; }

/* ── Section ── */
.section {
  position: relative; z-index: 1;
  max-width: 1200px; margin: 0 auto;
  padding: 80px 24px;
}
.section-header { text-align: center; margin-bottom: 48px; }
.section-tag {
  display: inline-block; padding: 4px 14px; border-radius: 100px;
  background: var(--purple-dim); color: var(--purple-light);
  font-size: 0.78rem; font-weight: 700; text-transform: uppercase;
  letter-spacing: 1px; margin-bottom: 12px;
}
.section-title {
  font-size: clamp(1.8rem, 4vw, 2.8rem);
  font-weight: 800; margin-bottom: 12px;
}
.section-desc { color: var(--text-secondary); font-size: 1.05rem; max-width: 600px; margin: 0 auto; }

/* ── Grade Selector ── */
.grade-selector {
  display: flex; flex-direction: column; align-items: center; gap: 16px;
  margin-bottom: 36px;
}
.grade-selector-label {
  font-size: 0.85rem; font-weight: 700; color: var(--text-muted);
  text-transform: uppercase; letter-spacing: 0.8px;
}
.grade-buttons { display: flex; gap: 12px; flex-wrap: wrap; justify-content: center; }
.grade-btn {
  display: flex; flex-direction: column; align-items: center; gap: 2px;
  padding: 14px 24px; border-radius: 14px; cursor: pointer;
  border: 1.5px solid rgba(255,255,255,0.08);
  background: rgba(255,255,255,0.03);
  color: var(--text-secondary); font-family: 'Inter', sans-serif;
  font-size: 0.95rem; font-weight: 700; transition: var(--transition);
  min-width: 150px;
}
.grade-btn:hover {
  border-color: rgba(255,255,255,0.2); background: rgba(255,255,255,0.07);
  color: var(--text-primary); transform: translateY(-2px);
}
.grade-btn.active {
  border-color: var(--purple); background: rgba(124,58,237,0.15);
  color: var(--purple-light);
  box-shadow: 0 0 20px rgba(124,58,237,0.25);
}
.grade-btn-sub {
  font-size: 0.72rem; font-weight: 500; color: var(--text-muted);
  letter-spacing: 0.3px;
}
.grade-btn.active .grade-btn-sub { color: var(--purple-light); opacity: 0.8; }

/* ── Level Cards ── */
.levels-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(320px,1fr)); gap: 24px; }

.level-card {
  position: relative;
  background: var(--bg-card);
  border: 1px solid var(--glass-border);
  border-radius: var(--radius-xl);
  padding: 32px;
  cursor: pointer;
  transition: var(--transition);
  overflow: hidden;
  text-decoration: none;
  display: block;
}
.level-card::before {
  content: ''; position: absolute; inset: 0; border-radius: inherit;
  background: linear-gradient(135deg, transparent, var(--card-color, rgba(124,58,237,0.05)));
  opacity: 0; transition: var(--transition);
}
.level-card:hover { transform: translateY(-6px); border-color: var(--card-color, var(--purple)); box-shadow: 0 20px 60px rgba(0,0,0,0.4); }
.level-card:hover::before { opacity: 1; }
.level-card-icon { font-size: 2.5rem; margin-bottom: 16px; }
.level-card-tag {
  display: inline-flex; align-items: center; gap: 6px;
  padding: 4px 12px; border-radius: 100px;
  font-size: 0.75rem; font-weight: 700;
  margin-bottom: 12px;
}
.level-card-title { font-size: 1.4rem; font-weight: 800; margin-bottom: 8px; }
.level-card-desc { color: var(--text-secondary); font-size: 0.9rem; margin-bottom: 20px; line-height: 1.6; }
.level-card-lessons { display: flex; align-items: center; gap: 8px; color: var(--text-muted); font-size: 0.85rem; }
.level-card-progress { margin-top: 20px; }
.progress-label { display: flex; justify-content: space-between; font-size: 0.8rem; color: var(--text-muted); margin-bottom: 6px; }
.progress-bar-bg { height: 6px; background: rgba(255,255,255,0.08); border-radius: 3px; overflow: hidden; }
.progress-bar-fill { height: 100%; border-radius: 3px; transition: width 1s ease; }

/* ── Features Grid ── */
.features-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(250px,1fr)); gap: 20px; }
.feature-card {
  background: var(--bg-card); border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg); padding: 28px;
  transition: var(--transition);
}
.feature-card:hover { background: var(--bg-card-hover); border-color: var(--purple); transform: translateY(-3px); }
.feature-icon {
  width: 52px; height: 52px; border-radius: 14px;
  display: flex; align-items: center; justify-content: center;
  font-size: 1.5rem; margin-bottom: 16px;
}
.feature-title { font-size: 1rem; font-weight: 700; margin-bottom: 8px; }
.feature-desc { color: var(--text-secondary); font-size: 0.875rem; line-height: 1.6; }

/* ── Footer ── */
footer {
  position: relative; z-index: 1;
  border-top: 1px solid var(--glass-border);
  padding: 40px 24px; text-align: center;
  color: var(--text-muted); font-size: 0.875rem;
}

/* ── Animations ── */
@keyframes fadeInDown { from{opacity:0;transform:translateY(-20px)}to{opacity:1;transform:translateY(0)} }
@keyframes fadeInUp { from{opacity:0;transform:translateY(20px)}to{opacity:1;transform:translateY(0)} }
@keyframes fadeIn { from{opacity:0}to{opacity:1} }
@keyframes shimmer { 0%{background-position:-200%}100%{background-position:200%} }

/* ── Lesson Page Layout ── */
.lesson-layout {
  display: flex; height: 100vh; padding-top: 64px;
  position: relative; z-index: 1;
}

/* Sidebar */
.sidebar {
  width: 280px; flex-shrink: 0;
  background: var(--bg-secondary);
  border-right: 1px solid var(--glass-border);
  overflow-y: auto; display: flex; flex-direction: column;
  position: sticky; top: 64px; height: calc(100vh - 64px);
}
.sidebar-header {
  padding: 20px 16px 12px;
  border-bottom: 1px solid var(--glass-border);
}
.sidebar-title { font-size: 0.75rem; font-weight: 700; text-transform: uppercase; letter-spacing: 1px; color: var(--text-muted); }
.sidebar-search {
  margin-top: 12px; position: relative;
}
.sidebar-search input {
  width: 100%; padding: 8px 12px 8px 32px; border-radius: 8px;
  background: var(--glass); border: 1px solid var(--glass-border);
  color: var(--text-primary); font-size: 0.85rem; font-family: inherit;
  outline: none; transition: var(--transition);
}
.sidebar-search input:focus { border-color: var(--purple); }
.sidebar-search-icon { position: absolute; left: 10px; top: 50%; transform: translateY(-50%); color: var(--text-muted); font-size: 0.8rem; }

.sidebar-level { padding: 12px 8px 4px; }
.sidebar-level-header {
  display: flex; align-items: center; gap: 8px;
  padding: 8px; border-radius: 8px; cursor: pointer;
  font-size: 0.8rem; font-weight: 700; text-transform: uppercase;
  letter-spacing: 0.5px; color: var(--text-muted);
  transition: var(--transition);
}
.sidebar-level-header:hover { color: var(--text-primary); }

.sidebar-lesson {
  display: flex; align-items: center; gap: 10px;
  padding: 10px 12px; border-radius: 10px; cursor: pointer;
  text-decoration: none; color: var(--text-secondary);
  font-size: 0.875rem; transition: var(--transition);
  margin-bottom: 2px; position: relative;
}
.sidebar-lesson:hover { background: var(--glass); color: var(--text-primary); }
.sidebar-lesson.active {
  background: var(--purple-dim); color: var(--purple-light);
  border: 1px solid rgba(124,58,237,0.3);
}
.sidebar-lesson-icon { font-size: 1rem; flex-shrink: 0; width: 22px; text-align: center; }
.sidebar-lesson-name { flex: 1; font-weight: 500; }
.sidebar-lesson-check {
  width: 18px; height: 18px; border-radius: 50%; flex-shrink: 0;
  border: 2px solid var(--glass-border); display: flex; align-items: center; justify-content: center;
  font-size: 0.65rem;
}
.sidebar-lesson-check.done { background: var(--green); border-color: var(--green); color: white; }

/* Main Content */
.lesson-main {
  flex: 1; overflow-y: auto;
  display: flex; flex-direction: column;
}
.lesson-content {
  max-width: 900px; width: 100%; margin: 0 auto;
  padding: 40px 32px 100px;
}

/* Lesson Header */
.lesson-header { margin-bottom: 40px; }
.lesson-header-top {
  display: flex; align-items: center; gap: 12px; margin-bottom: 16px;
}
.lesson-level-badge {
  padding: 4px 12px; border-radius: 100px;
  font-size: 0.75rem; font-weight: 700;
}
.lesson-icon-big { font-size: 2rem; }
.lesson-title-big {
  font-size: clamp(1.5rem, 3vw, 2.2rem); font-weight: 800;
  margin-bottom: 8px;
}
.lesson-meta {
  display: flex; align-items: center; gap: 20px;
  color: var(--text-muted); font-size: 0.85rem;
}
.lesson-meta span { display: flex; align-items: center; gap: 5px; }

/* Theory Content */
.theory-content {
  background: var(--bg-card); border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg); padding: 32px;
  margin-bottom: 32px;
}
.theory-content h2 {
  font-size: 1.5rem; font-weight: 800; margin-bottom: 16px;
  background: linear-gradient(135deg, var(--purple-light), var(--cyan));
  -webkit-background-clip: text; background-clip: text;
  -webkit-text-fill-color: transparent;
}
.theory-content h3 { font-size: 1.1rem; font-weight: 700; margin: 24px 0 12px; color: var(--text-primary); }
.theory-content p { color: var(--text-secondary); margin-bottom: 16px; line-height: 1.7; }
.theory-content ul, .theory-content ol { padding-left: 20px; margin-bottom: 16px; }
.theory-content li { color: var(--text-secondary); margin-bottom: 8px; line-height: 1.6; }
.theory-content code {
  font-family: 'Fira Code', monospace;
  background: rgba(124,58,237,0.15); color: var(--purple-light);
  padding: 2px 6px; border-radius: 5px; font-size: 0.875em;
}
.info-box {
  display: flex; gap: 12px; padding: 16px 20px; border-radius: 10px;
  background: var(--cyan-dim); border: 1px solid rgba(6,182,212,0.2);
  margin: 20px 0;
}
.info-icon { font-size: 1.2rem; flex-shrink: 0; }
.info-box p, .info-box div { color: var(--text-secondary); font-size: 0.9rem; }
.warning-box {
  display: flex; gap: 12px; padding: 16px 20px; border-radius: 10px;
  background: rgba(245,158,11,0.1); border: 1px solid rgba(245,158,11,0.2);
  margin: 20px 0;
}
.feature-list { list-style: none; padding: 0; }
.feature-list li { padding: 8px 0; color: var(--text-secondary); }
.code-example {
  background: #0d1117; border: 1px solid var(--glass-border);
  border-radius: 10px; overflow: hidden; margin: 16px 0;
}
.code-example pre {
  padding: 20px; overflow-x: auto; font-family: 'Fira Code', monospace;
  font-size: 0.875rem; line-height: 1.6; color: #e2e8f0;
}
.code-example pre code { background: none; color: inherit; padding: 0; }
.code-output {
  border-top: 1px solid var(--glass-border);
  background: rgba(16,185,129,0.05);
  padding: 12px 20px; font-family: 'Fira Code', monospace;
  font-size: 0.825rem; color: var(--green);
}
.type-grid { display: grid; grid-template-columns: repeat(4,1fr); gap: 12px; margin: 16px 0; }
.type-card {
  border-radius: 10px; padding: 16px; text-align: center;
  border: 1px solid var(--glass-border);
}
.type-card span { font-family: 'Fira Code', monospace; font-weight: 700; font-size: 1rem; }
.type-card p { font-size: 0.78rem; color: var(--text-muted); margin-top: 6px; }
.type-card.str { background: rgba(124,58,237,0.1); border-color: rgba(124,58,237,0.3); }
.type-card.str span { color: var(--purple-light); }
.type-card.int { background: rgba(6,182,212,0.1); border-color: rgba(6,182,212,0.3); }
.type-card.int span { color: var(--cyan); }
.type-card.float { background: rgba(16,185,129,0.1); border-color: rgba(16,185,129,0.3); }
.type-card.float span { color: var(--green); }
.type-card.bool { background: rgba(245,158,11,0.1); border-color: rgba(245,158,11,0.3); }
.type-card.bool span { color: var(--orange); }
.operator-grid { display: flex; flex-wrap: wrap; gap: 12px; padding: 16px; background: var(--glass); border-radius: 10px; margin: 12px 0; font-size: 0.9rem; }
.comparison-box { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin: 16px 0; }
.comparison-box div { padding: 16px; background: var(--glass); border-radius: 10px; font-size: 0.9rem; color: var(--text-secondary); }

/* ── Exercise Panel ── */
.section-divider {
  border: none;
  height: 2px;
  background: linear-gradient(90deg, transparent, rgba(124,58,237,0.5), transparent);
  margin: 60px 0 40px 0;
}
.exercise-panel { margin-top: 20px; }
.exercise-header {
  display: flex; align-items: center; justify-content: space-between;
  margin-bottom: 20px;
}
.exercise-title { font-size: 1.3rem; font-weight: 800; }
.exercise-tabs { display: flex; gap: 8px; flex-wrap: wrap; }
.ex-tab {
  padding: 8px 16px; border-radius: 100px; border: 1px solid var(--glass-border);
  background: var(--glass); color: var(--text-secondary);
  cursor: pointer; font-size: 0.85rem; font-weight: 600; font-family: inherit;
  transition: var(--transition); display: flex; align-items: center; gap: 6px;
}
.ex-tab:hover { border-color: var(--purple); color: var(--text-primary); }
.ex-tab.active { background: var(--purple-dim); border-color: var(--purple); color: var(--purple-light); }
.ex-tab.done::after { content:'✓'; }
.difficulty-badge {
  padding: 2px 8px; border-radius: 100px; font-size: 0.7rem; font-weight: 700;
}
.difficulty-easy { background: var(--green-dim); color: var(--green); }
.difficulty-medium { background: rgba(245,158,11,0.15); color: var(--orange); }
.difficulty-hard { background: rgba(239,68,68,0.15); color: var(--red); }

.exercise-card {
  background: var(--bg-card); border: 1px solid var(--glass-border);
  border-radius: var(--radius-lg); overflow: hidden;
}
.exercise-desc {
  padding: 24px 28px; border-bottom: 1px solid var(--glass-border);
}
.exercise-desc h3 { font-size: 1.1rem; font-weight: 700; margin-bottom: 10px; }
.exercise-desc p { color: var(--text-secondary); font-size: 0.9rem; line-height: 1.6; }

/* ── Code Editor ── */
.editor-container { position: relative; }
.editor-toolbar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 10px 16px; background: #0d1117;
  border-bottom: 1px solid rgba(255,255,255,0.06);
}
.editor-lang { font-size: 0.75rem; font-weight: 600; color: var(--purple-light); display: flex; align-items: center; gap: 6px; }
.editor-actions { display: flex; gap: 8px; }
.btn-run {
  padding: 7px 20px; border-radius: 8px; border: none; cursor: pointer;
  font-size: 0.875rem; font-weight: 700; font-family: inherit;
  background: linear-gradient(135deg, var(--green), #059669);
  color: white; transition: var(--transition);
  display: flex; align-items: center; gap: 6px;
}
.btn-run:hover { transform: translateY(-1px); box-shadow: 0 4px 16px rgba(16,185,129,0.4); }
.btn-run:disabled { opacity: 0.5; cursor: not-allowed; transform: none; }
.btn-hint {
  padding: 7px 16px; border-radius: 8px; border: 1px solid var(--glass-border); cursor: pointer;
  font-size: 0.875rem; font-weight: 600; font-family: inherit;
  background: var(--glass); color: var(--text-secondary); transition: var(--transition);
}
.btn-hint:hover { border-color: var(--orange); color: var(--orange); }
.btn-reset {
  padding: 7px 12px; border-radius: 8px; border: 1px solid var(--glass-border); cursor: pointer;
  font-size: 0.875rem; font-family: inherit;
  background: var(--glass); color: var(--text-muted); transition: var(--transition);
}
.btn-reset:hover { color: var(--red); border-color: var(--red); }

.cm-editor-wrap { min-height: 180px; max-height: 400px; overflow: auto; }

/* ── Output Panel ── */
.output-panel {
  border-top: 1px solid rgba(255,255,255,0.06);
  background: #0a0e1a;
}
.output-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 10px 16px; border-bottom: 1px solid rgba(255,255,255,0.04);
}
.output-label { font-size: 0.75rem; font-weight: 700; text-transform: uppercase; letter-spacing: 1px; color: var(--text-muted); display: flex; align-items: center; gap: 6px; }
.output-status { font-size: 0.75rem; font-weight: 600; }
.output-status.success { color: var(--green); }
.output-status.error { color: var(--red); }
.output-status.running { color: var(--cyan); }
.output-content {
  padding: 16px; font-family: 'Fira Code', monospace;
  font-size: 0.8rem; line-height: 1.7;
  min-height: 80px; max-height: 200px; overflow-y: auto;
  white-space: pre-wrap; word-break: break-all;
}
.output-content.success { color: var(--green); }
.output-content.error { color: #f87171; }
.output-placeholder { color: var(--text-muted); font-style: italic; }
.output-loading {
  display: flex; align-items: center; gap: 8px;
  color: var(--cyan); font-size: 0.85rem;
}
.spinner {
  width: 16px; height: 16px; border-radius: 50%;
  border: 2px solid rgba(6,182,212,0.3);
  border-top-color: var(--cyan);
  animation: spin 0.8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }

/* ── AI Feedback ── */
.ai-panel {
  margin-top: 20px; border-radius: var(--radius-lg);
  border: 1px solid rgba(124,58,237,0.3);
  background: linear-gradient(135deg, rgba(124,58,237,0.05), rgba(6,182,212,0.05));
  overflow: hidden;
}
.ai-panel-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 16px 20px; border-bottom: 1px solid rgba(124,58,237,0.2);
}
.ai-panel-title {
  display: flex; align-items: center; gap: 10px;
  font-weight: 700; font-size: 0.95rem;
}
.ai-icon {
  width: 32px; height: 32px; border-radius: 8px;
  background: linear-gradient(135deg, var(--purple), var(--cyan));
  display: flex; align-items: center; justify-content: center; font-size: 1rem;
}
.btn-ai-check {
  padding: 8px 20px; border-radius: 10px; border: none; cursor: pointer;
  font-size: 0.85rem; font-weight: 700; font-family: inherit;
  background: linear-gradient(135deg, var(--purple), var(--purple-light));
  color: white; transition: var(--transition);
  display: flex; align-items: center; gap: 6px;
}
.btn-ai-check:hover { transform: translateY(-1px); box-shadow: 0 4px 16px rgba(124,58,237,0.4); }
.btn-ai-check:disabled { opacity: 0.5; cursor: not-allowed; transform: none; }
.ai-content { padding: 20px; text-align: left; }
.ai-placeholder { color: var(--text-muted); font-size: 0.875rem; text-align: center; padding: 20px 0; }
.ai-score-row {
  display: flex; align-items: center; gap: 16px; margin-bottom: 20px;
  padding: 16px; background: var(--glass); border-radius: 12px;
}
.ai-score-big {
  font-size: 3rem; font-weight: 900;
  background: linear-gradient(135deg, var(--purple-light), var(--cyan));
  -webkit-background-clip: text; background-clip: text;
  -webkit-text-fill-color: transparent;
  flex-shrink: 0;
}
.ai-score-label { font-size: 0.8rem; color: var(--text-muted); }
.ai-score-grade { font-size: 1.1rem; font-weight: 700; }
.ai-feedback-text { color: var(--text-secondary); font-size: 0.9rem; line-height: 1.8; }
.ai-feedback-section { margin-bottom: 12px; }
.ai-feedback-section strong { color: var(--text-primary); }
.ai-loading { display: flex; align-items: center; gap: 10px; color: var(--purple-light); font-size: 0.875rem; }
.ai-typing { display: flex; gap: 4px; }
.ai-typing span { width: 6px; height: 6px; border-radius: 50%; background: var(--purple-light); animation: bounce 0.8s infinite; }
.ai-typing span:nth-child(2) { animation-delay: 0.15s; }
.ai-typing span:nth-child(3) { animation-delay: 0.3s; }
@keyframes bounce { 0%,100%{transform:translateY(0)}50%{transform:translateY(-6px)} }

/* ── Navigation Buttons ── */
.lesson-nav-btns {
  display: flex; justify-content: space-between;
  margin-top: 40px; padding-top: 24px;
  border-top: 1px solid var(--glass-border);
}
.btn-lesson-nav {
  padding: 12px 24px; border-radius: 10px; border: 1px solid var(--glass-border); cursor: pointer;
  font-size: 0.9rem; font-weight: 600; font-family: inherit;
  background: var(--glass); color: var(--text-primary); transition: var(--transition);
  display: flex; align-items: center; gap: 8px;
}
.btn-lesson-nav:hover { border-color: var(--purple); background: var(--purple-dim); color: var(--purple-light); }
.btn-lesson-nav:disabled { opacity: 0.3; cursor: not-allowed; }
.btn-complete {
  padding: 12px 28px; border-radius: 10px; border: none; cursor: pointer;
  font-size: 0.9rem; font-weight: 700; font-family: inherit;
  background: linear-gradient(135deg, var(--green), #059669);
  color: white; transition: var(--transition);
  display: flex; align-items: center; gap: 8px;
}
.btn-complete:hover { transform: translateY(-2px); box-shadow: 0 6px 20px rgba(16,185,129,0.4); }

/* ── Hint Toast ── */
.hint-toast {
  position: fixed; bottom: 24px; right: 24px; z-index: 1000;
  max-width: 360px; padding: 16px 20px; border-radius: 12px;
  background: rgba(15, 20, 40, 0.95);
  border: 1px solid var(--orange);
  backdrop-filter: blur(20px);
  box-shadow: 0 8px 32px rgba(0,0,0,0.4);
  animation: slideInRight 0.3s ease;
}
.hint-toast-title { font-size: 0.85rem; font-weight: 700; color: var(--orange); margin-bottom: 6px; }
.hint-toast-text { font-size: 0.875rem; color: var(--text-secondary); line-height: 1.5; }
@keyframes slideInRight { from{transform:translateX(100px);opacity:0}to{transform:translateX(0);opacity:1} }

/* ── Modal ── */
.modal-backdrop {
  position: fixed; inset: 0; z-index: 200;
  background: rgba(0,0,0,0.7); backdrop-filter: blur(8px);
  display: flex; align-items: center; justify-content: center;
  padding: 20px; animation: fadeIn 0.2s ease;
}
.modal {
  background: var(--bg-secondary); border: 1px solid var(--glass-border);
  border-radius: var(--radius-xl); padding: 32px;
  max-width: 480px; width: 100%;
  animation: fadeInDown 0.3s ease;
}
.modal-icon { font-size: 2.5rem; text-align: center; margin-bottom: 16px; }
.modal-title { font-size: 1.3rem; font-weight: 800; text-align: center; margin-bottom: 8px; }
.modal-desc { color: var(--text-secondary); text-align: center; font-size: 0.9rem; margin-bottom: 24px; }
.modal-input {
  width: 100%; padding: 12px 16px; border-radius: 10px;
  background: var(--glass); border: 1px solid var(--glass-border);
  color: var(--text-primary); font-size: 0.9rem; font-family: 'Fira Code', monospace;
  outline: none; transition: var(--transition); margin-bottom: 16px;
}
.modal-input:focus { border-color: var(--purple); }
.modal-actions { display: flex; gap: 12px; }
.modal-btn-cancel {
  flex: 1; padding: 12px; border-radius: 10px; border: 1px solid var(--glass-border); cursor: pointer;
  font-size: 0.9rem; font-weight: 600; font-family: inherit;
  background: var(--glass); color: var(--text-secondary); transition: var(--transition);
}
.modal-btn-cancel:hover { background: var(--bg-card-hover); }
.modal-btn-save {
  flex: 2; padding: 12px; border-radius: 10px; border: none; cursor: pointer;
  font-size: 0.9rem; font-weight: 700; font-family: inherit;
  background: linear-gradient(135deg, var(--purple), var(--purple-light));
  color: white; transition: var(--transition);
}
.modal-btn-save:hover { box-shadow: 0 4px 20px rgba(124,58,237,0.4); }

/* ── Textarea Code Editor ── */
.code-textarea-wrap {
  position: relative;
  display: flex;
  background: #0d1117;
  min-height: 200px;
  max-height: 380px;
  overflow: hidden;
}
.line-numbers {
  display: flex;
  flex-direction: column;
  padding: 16px 0;
  min-width: 48px;
  background: #0d1117;
  border-right: 1px solid rgba(255,255,255,0.06);
  text-align: right;
  user-select: none;
  overflow: hidden;
  flex-shrink: 0;
}
.line-numbers span {
  font-family: 'Fira Code', monospace;
  font-size: 13px;
  line-height: 1.6;
  color: #3d4451;
  padding: 0 10px;
  display: block;
}
.code-textarea {
  flex: 1;
  min-height: 200px;
  max-height: 380px;
  background: #0d1117;
  color: #e2e8f0;
  font-family: 'Fira Code', monospace;
  font-size: 14px;
  line-height: 1.6;
  padding: 16px 20px;
  border: none;
  outline: none;
  resize: vertical;
  overflow: auto;
  tab-size: 4;
  white-space: pre;
  caret-color: #a855f7;
  letter-spacing: 0.02em;
}
.code-textarea::selection { background: rgba(124,58,237,0.3); }
.code-textarea:focus { outline: none; }
.textarea-holder { background: #0d1117; }

/* ── Pyodide Loading ── */
.pyodide-loading {
  display: flex; align-items: center; justify-content: center;
  gap: 10px; padding: 60px 20px; flex-direction: column;
  color: var(--text-muted); font-size: 0.875rem;
}
.pyodide-progress {
  width: 200px; height: 4px; background: var(--glass-border);
  border-radius: 2px; overflow: hidden;
}
.pyodide-progress-fill {
  height: 100%; border-radius: 2px;
  background: linear-gradient(90deg, var(--purple), var(--cyan));
  animation: loadProgress 3s ease-out forwards;
}
@keyframes loadProgress { from{width:0}to{width:90%} }

/* ── Input Dialog ── */
.input-dialog-overlay {
  position: fixed; inset: 0; z-index: 500;
  background: rgba(0,0,0,0.8); backdrop-filter: blur(8px);
  display: flex; align-items: center; justify-content: center;
}
.input-dialog {
  background: var(--bg-secondary); border: 1px solid var(--purple);
  border-radius: var(--radius-lg); padding: 28px; width: 360px;
  animation: fadeInDown 0.2s ease;
}
.input-dialog-prompt { font-size: 0.95rem; margin-bottom: 16px; color: var(--text-primary); }
.input-dialog-field {
  width: 100%; padding: 10px 14px; border-radius: 8px;
  background: var(--glass); border: 1px solid var(--purple);
  color: var(--text-primary); font-size: 0.95rem; font-family: 'Fira Code', monospace;
  outline: none; margin-bottom: 16px;
}
.input-dialog-btn {
  width: 100%; padding: 10px; border-radius: 8px; border: none; cursor: pointer;
  font-size: 0.9rem; font-weight: 700; font-family: inherit;
  background: linear-gradient(135deg, var(--purple), var(--purple-light));
  color: white;
}

/* ── AI Feedback — Detailed UI ── */
/* ── AI Feedback Result — Redesigned ── */

/* Fade-in animation for the whole result */
@keyframes fbFadeUp {
  from { opacity: 0; transform: translateY(14px); }
  to   { opacity: 1; transform: translateY(0); }
}
.ai-fb-wrap {
  animation: fbFadeUp 0.35s cubic-bezier(0.22,1,0.36,1) both;
  display: flex; flex-direction: column; gap: 12px;
  text-align: left;
}

/* ── Score Hero ── */
.ai-score-hero {
  display: flex; align-items: center; gap: 20px;
  padding: 20px 24px; border-radius: 16px;
  position: relative; overflow: hidden;
}
.ai-score-hero::before {
  content: ''; position: absolute; inset: 0;
  background: radial-gradient(ellipse at 10% 50%, rgba(255,255,255,0.04) 0%, transparent 70%);
  pointer-events: none;
}
.ai-score-ring-wrap {
  position: relative; width: 84px; height: 84px; flex-shrink: 0;
}
.ai-score-ring {
  width: 84px; height: 84px;
  transform: rotate(-90deg);
}
.ai-score-ring-bg {
  fill: none; stroke: rgba(255,255,255,0.08); stroke-width: 6;
}
.ai-score-ring-fill {
  fill: none; stroke-width: 6; stroke-linecap: round;
  stroke-dasharray: 226; /* 2π × 36 */
  stroke-dashoffset: 226;
  transition: stroke-dashoffset 1s cubic-bezier(0.22,1,0.36,1);
}
.ai-score-ring-num {
  position: absolute; inset: 0;
  display: flex; flex-direction: column;
  align-items: center; justify-content: center;
  font-size: 1.6rem; font-weight: 900; line-height: 1;
  font-variant-numeric: tabular-nums;
}
.ai-score-ring-slash {
  font-size: 0.58rem; color: var(--text-muted);
  font-weight: 500; margin-top: 1px;
}

.ai-score-details { flex: 1; display: flex; flex-direction: column; gap: 8px; }
.ai-score-top-row {
  display: flex; align-items: center; gap: 8px; flex-wrap: wrap;
}
.ai-grade-pill {
  font-size: 0.8rem; font-weight: 800; padding: 3px 14px;
  border-radius: 100px; letter-spacing: 0.3px;
}
.ai-mode-chip {
  font-size: 0.68rem; font-weight: 700; padding: 3px 10px;
  border-radius: 100px; border: 1px solid;
}
.ai-score-bar-wrap {
  display: flex; flex-direction: column; gap: 4px;
}
.ai-score-bar-label {
  font-size: 0.72rem; color: var(--text-muted); display: flex;
  justify-content: space-between;
}
.ai-score-bar-track {
  height: 6px; border-radius: 100px;
  background: rgba(255,255,255,0.07); overflow: hidden;
}
.ai-score-bar-fill {
  height: 100%; border-radius: 100px;
  width: 0%; transition: width 1s cubic-bezier(0.22,1,0.36,1);
}
.ai-score-summary {
  font-size: 0.875rem; color: var(--text-secondary); line-height: 1.55;
}
.ai-score-emoji-badge {
  font-size: 2.8rem; flex-shrink: 0; line-height: 1;
  filter: drop-shadow(0 2px 12px rgba(0,0,0,0.4));
}

/* ── All-good banner ── */
.ai-all-good {
  display: flex; align-items: center; gap: 16px;
  padding: 16px 20px; border-radius: 14px;
  background: linear-gradient(135deg, rgba(16,185,129,0.15), rgba(6,182,212,0.1));
  border: 1px solid rgba(16,185,129,0.25);
  border-left: 4px solid #10b981;
  color: var(--text-primary); font-size: 0.9rem;
  line-height: 1.5;
  box-shadow: 0 4px 20px rgba(16,185,129,0.08);
}
.ai-all-good-icon {
  font-size: 2.2rem; flex-shrink: 0;
  filter: drop-shadow(0 2px 8px rgba(16,185,129,0.3));
}

@media (max-width: 400px) {
  .ai-all-good {
    flex-direction: column;
    align-items: flex-start;
    gap: 10px;
    border-left: 1px solid rgba(16,185,129,0.25);
    border-top: 4px solid #10b981;
    padding: 16px;
  }
  .ai-all-good-icon {
    font-size: 1.8rem;
  }
}

/* ── Generic section card ── */
.ai-card {
  border-radius: 14px; overflow: hidden;
  background: rgba(255,255,255,0.025);
  border: 1px solid rgba(255,255,255,0.07);
  backdrop-filter: blur(6px);
}
.ai-card-header {
  display: flex; align-items: center; gap: 8px;
  padding: 11px 16px;
  border-bottom: 1px solid rgba(255,255,255,0.06);
  font-size: 0.78rem; font-weight: 800;
  text-transform: uppercase; letter-spacing: 0.6px;
}
.ai-card-header-dot {
  width: 8px; height: 8px; border-radius: 50%; flex-shrink: 0;
}
.ai-card-body { padding: 14px 16px; display: flex; flex-direction: column; gap: 10px; }

/* ── Summary ── */
.ai-summary-body {
  font-size: 0.9rem; color: var(--text-secondary);
  line-height: 1.75; border-radius: 10px; padding: 14px 16px;
  background: rgba(255,255,255,0.03);
  border-left: 3px solid var(--purple);
}

/* ── Bug items ── */
.ai-bug-item {
  border-radius: 12px; overflow: hidden;
  border: 1px solid rgba(255,255,255,0.06);
}
.ai-bug-top {
  display: flex; align-items: center; justify-content: space-between;
  padding: 10px 14px;
}
.ai-bug-sev-chip {
  display: inline-flex; align-items: center; gap: 5px;
  font-size: 0.72rem; font-weight: 800; padding: 4px 10px;
  border-radius: 100px; border: 1px solid;
}
.ai-bug-loc {
  font-family: 'Fira Code', monospace; font-size: 0.72rem;
  color: var(--text-muted); background: rgba(255,255,255,0.05);
  padding: 3px 8px; border-radius: 6px;
}
.ai-bug-body { padding: 10px 14px 14px; display: flex; flex-direction: column; gap: 10px; }
.ai-bug-problem-text {
  font-size: 0.9rem; font-weight: 600; color: var(--text-primary); line-height: 1.5;
}
.ai-bug-explain {
  font-size: 0.8rem; color: var(--text-muted); line-height: 1.6;
  padding: 8px 12px; background: rgba(255,255,255,0.03);
  border-radius: 8px; border-left: 2px solid rgba(6,182,212,0.4);
}

/* Code compare blocks */
.ai-code-compare { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; }
.ai-code-compare:has(> :only-child) { grid-template-columns: 1fr; }
@supports not (selector(:has(*))) {
  .ai-code-compare { grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); }
}
.ai-code-block { border-radius: 10px; overflow: hidden; background: #070b16; border: 1px solid rgba(255,255,255,0.07); }
.ai-code-bad  { border-color: rgba(239,68,68,0.3); }
.ai-code-good { border-color: rgba(16,185,129,0.3); }
.ai-code-before { border-color: rgba(255,255,255,0.08); }
.ai-code-after  { border-color: rgba(124,58,237,0.35); }
.ai-code-label-tag {
  font-size: 0.68rem; font-weight: 700; text-transform: uppercase;
  letter-spacing: 0.5px; padding: 6px 12px;
  border-bottom: 1px solid rgba(255,255,255,0.06);
  background: rgba(255,255,255,0.03);
  text-align: left;
}
.ai-code-block pre {
  font-family: 'Fira Code', monospace; font-size: 0.8rem;
  color: #c9d5e8; padding: 12px; margin: 0;
  overflow-x: auto; line-height: 1.65; white-space: pre-wrap; word-break: break-word;
  text-align: left;
}

/* ── Missing items ── */
.ai-missing-item {
  display: flex; align-items: center; gap: 8px;
  padding: 9px 14px; border-radius: 10px;
  background: rgba(245,158,11,0.07);
  border: 1px solid rgba(245,158,11,0.2);
  font-size: 0.875rem; color: var(--text-secondary);
}
.ai-missing-dot {
  width: 7px; height: 7px; border-radius: 50%;
  background: #f59e0b; flex-shrink: 0;
}

/* ── Improvement items ── */
.ai-improv-item {
  border-radius: 12px; overflow: hidden;
  background: rgba(124,58,237,0.05);
  border: 1px solid rgba(124,58,237,0.15);
}
.ai-improv-top {
  display: flex; align-items: center; gap: 7px;
  padding: 9px 14px;
  border-bottom: 1px solid rgba(124,58,237,0.1);
  font-size: 0.72rem; font-weight: 800;
  text-transform: uppercase; letter-spacing: 0.5px;
  color: var(--purple-light);
}
.ai-improv-body { padding: 10px 14px 14px; display: flex; flex-direction: column; gap: 8px; text-align: left; }
.ai-improv-desc { font-size: 0.875rem; color: var(--text-secondary); line-height: 1.6; text-align: left; }

/* ── Strength items ── */
.ai-strength-list { display: flex; flex-direction: column; gap: 7px; }
.ai-strength-item {
  display: flex; align-items: center; gap: 10px;
  padding: 9px 14px; border-radius: 10px;
  background: rgba(16,185,129,0.07);
  border: 1px solid rgba(16,185,129,0.2);
  font-size: 0.875rem; color: var(--text-secondary);
}
.ai-strength-icon { font-size: 1rem; flex-shrink: 0; }

/* ── Action Plan ── */
.ai-action-body {
  font-size: 0.875rem; color: var(--text-secondary);
  line-height: 1.85; padding: 14px 16px;
}
.ai-action-step {
  display: flex; align-items: flex-start; gap: 10px;
  padding: 7px 0; border-bottom: 1px solid rgba(255,255,255,0.04);
}
.ai-action-step:last-child { border-bottom: none; padding-bottom: 0; }
.ai-action-step-num {
  width: 20px; height: 20px; border-radius: 50%; flex-shrink: 0;
  display: flex; align-items: center; justify-content: center;
  font-size: 0.68rem; font-weight: 800;
  background: rgba(6,182,212,0.15); color: var(--cyan);
  border: 1px solid rgba(6,182,212,0.3); margin-top: 1px;
}

@media (max-width: 600px) {
  .ai-code-compare { grid-template-columns: 1fr; }
  .ai-score-hero { flex-wrap: wrap; }
}

/* ── Celebration ── */
.celebration {
  position: fixed; inset: 0; z-index: 300;
  pointer-events: none; overflow: hidden;
}
.confetti {
  position: absolute; width: 10px; height: 10px; border-radius: 2px;
  animation: confettiFall 3s ease-in forwards;
}
@keyframes confettiFall {
  0% { transform: translateY(-10%) rotate(0deg); opacity: 1; }
  100% { transform: translateY(110vh) rotate(720deg); opacity: 0; }
}

/* ── Responsive ── */
@media (max-width: 768px) {
  .sidebar { display: none; }
  .lesson-main { width: 100%; }
  .lesson-content { padding: 24px 16px 80px; }
  .hero-title { font-size: 2.2rem; }
  .hero-stats { gap: 24px; }
  .type-grid { grid-template-columns: repeat(2,1fr); }
  .nav-links { display: none; }
}

/* ── Check Mode Toggle ── */
.check-mode-toggle {
  display: flex;
  align-items: center;
  background: rgba(255,255,255,0.05);
  border: 1px solid rgba(255,255,255,0.1);
  border-radius: 20px;
  padding: 3px;
  gap: 2px;
}
.mode-btn {
  padding: 5px 14px;
  border: none;
  border-radius: 16px;
  font-size: 0.78rem;
  font-weight: 600;
  cursor: pointer;
  background: transparent;
  color: var(--text-secondary);
  transition: all 0.2s ease;
  white-space: nowrap;
  font-family: 'Inter', sans-serif;
}
.mode-btn:hover {
  color: var(--text-primary);
  background: rgba(255,255,255,0.08);
}
.mode-btn-ai.active {
  background: rgba(124,58,237,0.3);
  color: var(--purple-light);
  box-shadow: 0 0 12px rgba(124,58,237,0.3);
}
.mode-btn-auto.active {
  background: rgba(249,115,22,0.25);
  color: #fb923c;
  box-shadow: 0 0 12px rgba(249,115,22,0.25);
}

/* ── Floating Code Preview Component & Desktop Hero Layout ── */
#floating-code {
  display: none;
  background: rgba(13,17,23,0.8);
  backdrop-filter: blur(20px);
  border: 1px solid rgba(124,58,237,0.3);
  border-radius: 16px;
  padding: 20px;
  width: 100%;
  max-width: 380px;
  box-sizing: border-box;
  box-shadow: 0 12px 40px rgba(0,0,0,0.5);
  margin: 0 auto;
}

@media (min-width: 1200px) {
  .hero {
    display: grid;
    grid-template-columns: 1.2fr 0.8fr;
    gap: 48px;
    text-align: left;
    max-width: 1200px;
    margin: 0 auto;
    align-items: center;
    justify-content: space-between;
  }
  .hero-content {
    text-align: left;
    max-width: 100%;
  }
  .hero-subtitle {
    margin: 0 0 40px 0;
  }
  .hero-actions {
    justify-content: flex-start;
  }
  .hero-stats {
    justify-content: flex-start;
  }
  #floating-code {
    display: block;
    margin-left: auto;
    margin-right: 0;
  }
}