/* ═══════════════════════════════════════════
   K8s Academy — Design System & Styles
   ═══════════════════════════════════════════ */

:root {
  --bg-primary: #080c18;
  --bg-secondary: #0f1629;
  --bg-card: #151d35;
  --bg-card-hover: #1a2440;
  --bg-sidebar: #0a1020;
  --bg-terminal: #0a0f1a;

  --k8s-blue: #326ce5;
  --k8s-blue-light: #5b8def;
  --k8s-blue-dark: #2555c0;
  --accent-cyan: #06d6a0;
  --accent-orange: #ff8c42;
  --accent-purple: #a78bfa;
  --accent-pink: #f472b6;
  --accent-red: #ef4444;
  --accent-yellow: #fbbf24;
  --accent-green: #34d399;
  --accent-teal: #2dd4bf;

  --text-primary: #f1f5f9;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;

  --border-color: rgba(148, 163, 184, 0.08);
  --border-glow: rgba(50, 108, 229, 0.3);

  --sidebar-width: 280px;

  --font-sans: 'Inter', -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;

  --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 20px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 8px 40px rgba(0, 0, 0, 0.5);
  --shadow-glow: 0 0 30px rgba(50, 108, 229, 0.15);

  --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: var(--font-sans);
  background: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  overflow: hidden;
  height: 100vh;
}

/* ─── Layout ─── */
#app { display: flex; height: 100vh; overflow: hidden; }

/* ─── Sidebar ─── */
#sidebar {
  width: var(--sidebar-width);
  min-width: var(--sidebar-width);
  background: var(--bg-sidebar);
  border-right: 1px solid var(--border-color);
  display: flex;
  flex-direction: column;
  overflow-y: auto;
  transition: transform var(--transition);
  z-index: 100;
}
.sidebar-header {
  padding: 24px 20px 16px;
  border-bottom: 1px solid var(--border-color);
}
.logo { display: flex; align-items: center; gap: 10px; margin-bottom: 16px; }
.logo-icon { font-size: 28px; animation: float 3s ease-in-out infinite; }
@keyframes float { 0%, 100% { transform: translateY(0); } 50% { transform: translateY(-4px); } }
.logo-text {
  font-size: 20px; font-weight: 800;
  background: linear-gradient(135deg, var(--k8s-blue), var(--accent-teal));
  -webkit-background-clip: text; background-clip: text; -webkit-text-fill-color: transparent;
  letter-spacing: -0.3px;
}
.progress-bar-container {
  width: 100%; height: 6px;
  background: rgba(255,255,255,0.06);
  border-radius: 10px; overflow: hidden;
}
.progress-bar {
  height: 100%; width: 0%;
  background: linear-gradient(90deg, var(--k8s-blue), var(--accent-teal));
  border-radius: 10px; transition: width 0.5s ease;
}
.progress-label {
  display: block; margin-top: 8px;
  font-size: 12px; color: var(--text-muted); font-weight: 500;
}
.nav-list { list-style: none; flex: 1; overflow-y: auto; padding: 12px 10px; }
.nav-item { margin-bottom: 2px; }
.nav-link {
  display: flex; align-items: center; gap: 10px;
  padding: 10px 14px; border-radius: 10px; cursor: pointer;
  color: var(--text-secondary); font-size: 13.5px; font-weight: 500;
  transition: all var(--transition); user-select: none; position: relative;
}
.nav-link:hover { background: rgba(255,255,255,0.04); color: var(--text-primary); }
.nav-link.active {
  background: rgba(50, 108, 229, 0.12); color: var(--k8s-blue-light); font-weight: 600;
}
.nav-link.active::before {
  content: ''; position: absolute; left: 0; top: 50%; transform: translateY(-50%);
  width: 3px; height: 60%; background: var(--k8s-blue); border-radius: 0 4px 4px 0;
}
.nav-link.completed { color: var(--accent-green); }
.nav-icon { font-size: 16px; width: 24px; text-align: center; flex-shrink: 0; }
.nav-check { margin-left: auto; font-size: 14px; opacity: 0; transition: opacity var(--transition); }
.nav-link.completed .nav-check { opacity: 1; }
.nav-section-title {
  padding: 16px 14px 6px; font-size: 10px; text-transform: uppercase;
  letter-spacing: 1.5px; color: var(--text-muted); font-weight: 700;
}
.sidebar-footer { padding: 12px 14px; border-top: 1px solid var(--border-color); }
.btn-reset {
  width: 100%; padding: 8px; background: transparent;
  border: 1px solid var(--border-color); color: var(--text-muted);
  border-radius: 8px; font-family: var(--font-sans); font-size: 12px;
  cursor: pointer; transition: all var(--transition);
}
.btn-reset:hover { border-color: var(--accent-red); color: var(--accent-red); background: rgba(239,68,68,0.08); }

/* ─── Main ─── */
#mainContent { flex: 1; display: flex; flex-direction: column; overflow: hidden; }
.topbar {
  display: none; align-items: center; gap: 12px; padding: 12px 20px;
  background: var(--bg-secondary); border-bottom: 1px solid var(--border-color);
}
.btn-menu { background: none; border: none; color: var(--text-primary); font-size: 22px; cursor: pointer; padding: 4px; }
.topbar-title { font-size: 14px; font-weight: 600; color: var(--text-secondary); }
.lesson-container { flex: 1; overflow-y: auto; padding: 40px; scroll-behavior: smooth; }
.lesson-nav {
  display: flex; justify-content: space-between; padding: 16px 40px;
  border-top: 1px solid var(--border-color); background: var(--bg-secondary);
}
.btn {
  padding: 10px 24px; border-radius: 10px; border: none;
  font-family: var(--font-sans); font-size: 14px; font-weight: 600;
  cursor: pointer; transition: all var(--transition); display: flex; align-items: center; gap: 6px;
}
.btn-prev { background: var(--bg-card); color: var(--text-secondary); border: 1px solid var(--border-color); }
.btn-prev:hover { background: var(--bg-card-hover); color: var(--text-primary); }
.btn-next {
  background: linear-gradient(135deg, var(--k8s-blue), var(--k8s-blue-dark));
  color: white; box-shadow: 0 4px 15px rgba(50,108,229,0.3);
}
.btn-next:hover { transform: translateY(-1px); box-shadow: 0 6px 20px rgba(50,108,229,0.4); }
.btn:disabled { opacity: 0.3; cursor: not-allowed; transform: none !important; }

/* ─── Lesson ─── */
.lesson { max-width: 860px; margin: 0 auto; animation: fadeIn 0.4s ease; }
@keyframes fadeIn { from { opacity: 0; transform: translateY(12px); } to { opacity: 1; transform: translateY(0); } }
.lesson-badge {
  display: inline-flex; align-items: center; gap: 6px; padding: 5px 14px;
  background: rgba(50,108,229,0.1); border: 1px solid rgba(50,108,229,0.2);
  border-radius: 20px; font-size: 12px; font-weight: 600; color: var(--k8s-blue-light);
  margin-bottom: 16px; text-transform: uppercase; letter-spacing: 0.5px;
}
.lesson h1 { font-size: 36px; font-weight: 900; line-height: 1.2; margin-bottom: 12px; letter-spacing: -0.5px; }
.lesson h1 .emoji { margin-right: 10px; }
.lesson-subtitle { font-size: 17px; color: var(--text-secondary); line-height: 1.6; margin-bottom: 36px; }
.lesson h2 {
  font-size: 22px; font-weight: 700; margin: 36px 0 16px; color: var(--text-primary);
  display: flex; align-items: center; gap: 10px;
}
.lesson h3 { font-size: 17px; font-weight: 700; margin: 24px 0 10px; color: var(--text-primary); }
.lesson p { margin-bottom: 16px; color: var(--text-secondary); font-size: 15px; line-height: 1.8; }
.lesson ul, .lesson ol { margin: 0 0 16px 20px; color: var(--text-secondary); }
.lesson li { margin-bottom: 8px; font-size: 15px; line-height: 1.7; }

/* ─── Visual Cards ─── */
.visual-box {
  background: var(--bg-card); border: 1px solid var(--border-color); border-radius: 16px;
  padding: 28px; margin: 24px 0; position: relative; overflow: hidden;
}
.visual-box::before {
  content: ''; position: absolute; top: 0; left: 0; right: 0; height: 2px;
  background: linear-gradient(90deg, var(--k8s-blue), var(--accent-teal), var(--accent-purple));
}
.visual-box.green::before { background: linear-gradient(90deg, var(--accent-green), var(--accent-cyan)); }
.visual-box.orange::before { background: linear-gradient(90deg, var(--accent-orange), var(--accent-yellow)); }
.visual-box.purple::before { background: linear-gradient(90deg, var(--accent-purple), var(--accent-pink)); }

.analogy-box {
  background: linear-gradient(135deg, rgba(50,108,229,0.08), rgba(6,214,160,0.05));
  border: 1px solid rgba(50,108,229,0.15); border-radius: 14px;
  padding: 24px; margin: 24px 0;
}
.analogy-box .analogy-emoji { font-size: 36px; margin-bottom: 12px; display: block; }
.analogy-box .analogy-title {
  font-size: 14px; font-weight: 700; color: var(--k8s-blue-light);
  text-transform: uppercase; letter-spacing: 1px; margin-bottom: 8px;
}
.analogy-box p { color: var(--text-primary); font-size: 15px; }

/* ─── Terminal ─── */
.terminal {
  background: var(--bg-terminal); border: 1px solid rgba(255,255,255,0.06);
  border-radius: 12px; margin: 20px 0; overflow: hidden; box-shadow: var(--shadow-md);
}
.terminal-header {
  display: flex; align-items: center; gap: 8px; padding: 10px 16px;
  background: rgba(255,255,255,0.03); border-bottom: 1px solid rgba(255,255,255,0.04);
}
.terminal-dot { width: 10px; height: 10px; border-radius: 50%; }
.terminal-dot.red { background: #ff5f57; }
.terminal-dot.yellow { background: #febc2e; }
.terminal-dot.green { background: #28c840; }
.terminal-title { margin-left: 8px; font-size: 12px; color: var(--text-muted); font-family: var(--font-mono); }
.terminal-body { padding: 18px 20px; overflow-x: auto; }
.terminal-body code {
  font-family: var(--font-mono); font-size: 13.5px; line-height: 1.8;
  color: #e2e8f0; white-space: pre; display: block;
}
.terminal-body .comment { color: #64748b; }
.terminal-body .command { color: var(--accent-cyan); }
.terminal-body .flag { color: var(--accent-orange); }
.terminal-body .string { color: var(--accent-yellow); }
.terminal-body .output { color: var(--text-muted); }
.terminal-body .keyword { color: var(--accent-purple); }
.terminal-body .success { color: var(--accent-green); }

.inline-code {
  font-family: var(--font-mono); font-size: 13px;
  background: rgba(50,108,229,0.12); color: var(--k8s-blue-light);
  padding: 2px 8px; border-radius: 5px; border: 1px solid rgba(50,108,229,0.15);
}

/* ─── Diagrams ─── */
.diagram {
  background: var(--bg-card); border: 1px solid var(--border-color); border-radius: 14px;
  padding: 30px; margin: 24px 0; display: flex; flex-direction: column;
  align-items: center; gap: 16px; overflow-x: auto;
}
.diagram-title {
  font-size: 13px; font-weight: 700; text-transform: uppercase;
  letter-spacing: 1.5px; color: var(--text-muted); margin-bottom: 8px;
}
.diagram-row { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; justify-content: center; }
.diagram-box {
  display: flex; flex-direction: column; align-items: center; gap: 6px;
  padding: 16px 20px; border-radius: 12px; font-size: 13px; font-weight: 600;
  min-width: 100px; text-align: center; transition: transform 0.3s ease; position: relative;
}
.diagram-box:hover { transform: translateY(-3px); }
.diagram-box.blue { background: rgba(50,108,229,0.15); border: 1px solid rgba(50,108,229,0.3); color: var(--k8s-blue-light); }
.diagram-box.green { background: rgba(6,214,160,0.12); border: 1px solid rgba(6,214,160,0.25); color: var(--accent-green); }
.diagram-box.orange { background: rgba(255,140,66,0.12); border: 1px solid rgba(255,140,66,0.25); color: var(--accent-orange); }
.diagram-box.purple { background: rgba(167,139,250,0.12); border: 1px solid rgba(167,139,250,0.25); color: var(--accent-purple); }
.diagram-box.pink { background: rgba(244,114,182,0.12); border: 1px solid rgba(244,114,182,0.25); color: var(--accent-pink); }
.diagram-box.teal { background: rgba(45,212,191,0.12); border: 1px solid rgba(45,212,191,0.25); color: var(--accent-teal); }
.diagram-box .box-icon { font-size: 24px; }
.diagram-arrow { font-size: 20px; color: var(--text-muted); }

/* ─── Tables ─── */
.compare-table {
  width: 100%; border-collapse: separate; border-spacing: 0; margin: 20px 0;
  border-radius: 12px; overflow: hidden; border: 1px solid var(--border-color);
}
.compare-table th {
  background: rgba(50,108,229,0.1); color: var(--k8s-blue-light); padding: 14px 18px;
  font-size: 13px; font-weight: 700; text-transform: uppercase; letter-spacing: 0.5px; text-align: left;
}
.compare-table td {
  padding: 12px 18px; font-size: 14px; color: var(--text-secondary);
  border-bottom: 1px solid var(--border-color); background: var(--bg-card);
}
.compare-table tr:last-child td { border-bottom: none; }
.compare-table tr:hover td { background: var(--bg-card-hover); }

/* ─── Quiz ─── */
.quiz {
  background: var(--bg-card); border: 1px solid var(--border-color);
  border-radius: 14px; padding: 28px; margin: 28px 0;
}
.quiz-title { font-size: 16px; font-weight: 700; margin-bottom: 4px; display: flex; align-items: center; gap: 8px; }
.quiz-question { color: var(--text-secondary); font-size: 15px; margin-bottom: 16px; }
.quiz-options { display: flex; flex-direction: column; gap: 8px; }
.quiz-option {
  display: flex; align-items: center; gap: 12px; padding: 12px 16px;
  border-radius: 10px; border: 1px solid var(--border-color); cursor: pointer;
  transition: all var(--transition); font-size: 14px; color: var(--text-secondary);
}
.quiz-option:hover { border-color: var(--k8s-blue); background: rgba(50,108,229,0.06); color: var(--text-primary); }
.quiz-option.selected { border-color: var(--k8s-blue); background: rgba(50,108,229,0.1); color: var(--text-primary); }
.quiz-option.correct { border-color: var(--accent-green); background: rgba(6,214,160,0.1); color: var(--accent-green); }
.quiz-option.wrong { border-color: var(--accent-red); background: rgba(239,68,68,0.1); color: var(--accent-red); }
.quiz-option .option-letter {
  width: 26px; height: 26px; display: flex; align-items: center; justify-content: center;
  border-radius: 7px; background: rgba(255,255,255,0.04); font-weight: 700; font-size: 12px; flex-shrink: 0;
}
.quiz-feedback { margin-top: 14px; padding: 12px 16px; border-radius: 10px; font-size: 14px; display: none; }
.quiz-feedback.show { display: block; }
.quiz-feedback.correct { background: rgba(6,214,160,0.08); border: 1px solid rgba(6,214,160,0.2); color: var(--accent-green); }
.quiz-feedback.wrong { background: rgba(239,68,68,0.08); border: 1px solid rgba(239,68,68,0.2); color: var(--accent-red); }

/* ─── Callouts ─── */
.callout {
  padding: 18px 20px; border-radius: 12px; margin: 20px 0;
  font-size: 14px; line-height: 1.7; display: flex; gap: 12px;
}
.callout-icon { font-size: 20px; flex-shrink: 0; margin-top: 2px; }
.callout.tip { background: rgba(6,214,160,0.06); border: 1px solid rgba(6,214,160,0.15); color: var(--accent-green); }
.callout.warn { background: rgba(251,191,36,0.06); border: 1px solid rgba(251,191,36,0.15); color: var(--accent-yellow); }
.callout.info { background: rgba(50,108,229,0.06); border: 1px solid rgba(50,108,229,0.15); color: var(--k8s-blue-light); }

/* ─── Steps ─── */
.steps { display: flex; flex-direction: column; gap: 16px; margin: 20px 0; }
.step-card {
  display: flex; gap: 16px; padding: 20px; background: var(--bg-card);
  border: 1px solid var(--border-color); border-radius: 14px; transition: all var(--transition);
}
.step-card:hover { border-color: var(--border-glow); box-shadow: var(--shadow-glow); }
.step-number {
  width: 36px; height: 36px; display: flex; align-items: center; justify-content: center;
  border-radius: 10px; background: linear-gradient(135deg, var(--k8s-blue), var(--k8s-blue-dark));
  color: white; font-weight: 800; font-size: 14px; flex-shrink: 0;
}
.step-content h4 { font-size: 15px; font-weight: 700; margin-bottom: 4px; color: var(--text-primary); }
.step-content p { font-size: 14px; color: var(--text-secondary); margin: 0; }

/* ─── Hero ─── */
.hero-card {
  text-align: center; padding: 60px 40px;
  background: linear-gradient(135deg, rgba(50,108,229,0.08), rgba(45,212,191,0.04), rgba(167,139,250,0.04));
  border: 1px solid rgba(50,108,229,0.15); border-radius: 20px; margin-bottom: 36px;
}
.hero-icon { font-size: 72px; display: block; margin-bottom: 16px; animation: float 3s ease-in-out infinite; }
.hero-card h1 {
  font-size: 42px; font-weight: 900; margin-bottom: 12px;
  background: linear-gradient(135deg, var(--k8s-blue-light), var(--accent-teal));
  -webkit-background-clip: text; background-clip: text; -webkit-text-fill-color: transparent;
}
.feature-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 16px; margin: 24px 0; }
.feature-item {
  padding: 24px; background: var(--bg-card); border: 1px solid var(--border-color);
  border-radius: 14px; text-align: center; transition: all var(--transition);
}
.feature-item:hover { border-color: var(--border-glow); transform: translateY(-3px); box-shadow: var(--shadow-glow); }
.feature-item .fi-icon { font-size: 32px; display: block; margin-bottom: 12px; }
.feature-item .fi-title { font-size: 15px; font-weight: 700; color: var(--text-primary); margin-bottom: 6px; }
.feature-item .fi-desc { font-size: 13px; color: var(--text-muted); line-height: 1.5; }

/* ─── Cheat Grid ─── */
.cheat-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin: 20px 0; }
.cheat-item { padding: 16px; background: var(--bg-card); border: 1px solid var(--border-color); border-radius: 12px; transition: all var(--transition); }
.cheat-item:hover { border-color: var(--border-glow); }
.cheat-cmd { font-family: var(--font-mono); font-size: 13px; color: var(--accent-cyan); margin-bottom: 6px; font-weight: 600; }
.cheat-desc { font-size: 12px; color: var(--text-muted); line-height: 1.5; }

/* ─── Architecture Blocks ─── */
.arch-block {
  border-radius: 14px; padding: 20px; margin: 8px 0;
}
.arch-block.control {
  background: rgba(50,108,229,0.06); border: 1px solid rgba(50,108,229,0.15);
}
.arch-block.worker {
  background: rgba(6,214,160,0.06); border: 1px solid rgba(6,214,160,0.15);
}
.arch-block-title {
  font-size: 12px; font-weight: 700; text-transform: uppercase;
  letter-spacing: 1.2px; margin-bottom: 12px;
}
.arch-block.control .arch-block-title { color: var(--k8s-blue-light); }
.arch-block.worker .arch-block-title { color: var(--accent-green); }
.arch-components {
  display: flex; flex-wrap: wrap; gap: 8px;
}
.arch-chip {
  padding: 8px 14px; border-radius: 8px; font-size: 12px; font-weight: 600;
  display: flex; align-items: center; gap: 6px;
}
.arch-chip.blue { background: rgba(50,108,229,0.15); color: var(--k8s-blue-light); }
.arch-chip.green { background: rgba(6,214,160,0.12); color: var(--accent-green); }
.arch-chip.orange { background: rgba(255,140,66,0.12); color: var(--accent-orange); }
.arch-chip.purple { background: rgba(167,139,250,0.12); color: var(--accent-purple); }
.arch-chip.teal { background: rgba(45,212,191,0.12); color: var(--accent-teal); }

/* ─── YAML highlight ─── */
.yaml-key { color: var(--k8s-blue-light); }
.yaml-val { color: var(--accent-green); }
.yaml-str { color: var(--accent-yellow); }

/* ─── Mini Pod Visualization ─── */
.pod-viz {
  display: flex; flex-wrap: wrap; gap: 10px; margin: 16px 0; justify-content: center;
}
.mini-pod {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 10px 16px; border-radius: 10px;
  font-size: 12px; font-weight: 600; animation: slideIn 0.5s ease forwards; opacity: 0;
}
.mini-pod:nth-child(1) { animation-delay: 0.05s; }
.mini-pod:nth-child(2) { animation-delay: 0.1s; }
.mini-pod:nth-child(3) { animation-delay: 0.15s; }
.mini-pod:nth-child(4) { animation-delay: 0.2s; }
.mini-pod:nth-child(5) { animation-delay: 0.25s; }
@keyframes slideIn { from { opacity: 0; transform: translateY(10px); } to { opacity: 1; transform: translateY(0); } }
.mini-pod.running { background: rgba(6,214,160,0.12); border: 1px solid rgba(6,214,160,0.25); color: var(--accent-green); }
.mini-pod.pending { background: rgba(251,191,36,0.12); border: 1px solid rgba(251,191,36,0.25); color: var(--accent-yellow); }
.mini-pod .status-dot { width: 7px; height: 7px; border-radius: 50%; }
.mini-pod.running .status-dot { background: var(--accent-green); box-shadow: 0 0 8px var(--accent-green); animation: pulse 2s ease-in-out infinite; }
.mini-pod.pending .status-dot { background: var(--accent-yellow); }
@keyframes pulse { 0%, 100% { opacity: 1; } 50% { opacity: 0.4; } }

/* ─── Responsive ─── */
@media (max-width: 900px) {
  #sidebar { position: fixed; top: 0; left: 0; height: 100vh; transform: translateX(-100%); box-shadow: var(--shadow-lg); }
  #sidebar.open { transform: translateX(0); }
  .topbar { display: flex; }
  .lesson-container { padding: 24px 20px; }
  .lesson-nav { padding: 12px 20px; }
  .hero-card { padding: 40px 20px; }
  .hero-card h1 { font-size: 28px; }
  .cheat-grid { grid-template-columns: 1fr; }
  .feature-grid { grid-template-columns: 1fr; }
}
.sidebar-overlay {
  display: none; position: fixed; top: 0; left: 0; width: 100%; height: 100%;
  background: rgba(0,0,0,0.6); z-index: 99; backdrop-filter: blur(4px);
}
.sidebar-overlay.show { display: block; }
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: transparent; }
::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.08); border-radius: 10px; }
::-webkit-scrollbar-thumb:hover { background: rgba(255,255,255,0.15); }