:root {
  --bg: #fff7ed;
  --text: #241407;
  --muted: #7c5b35;
  --primary: #d97706;
  --primary-dark: #92400e;
  --accent: #f59e0b;
  --soft: #ffedd5;
  --line: #fed7aa;
  --code-bg: #1f1308;
  --code-text: #fff7ed;
  --success: #15803d;
  --danger: #b91c1c;
  --info: #0369a1;
  --shadow: 0 18px 45px rgba(120, 53, 15, 0.14);
  --radius: 24px;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
  background:
    radial-gradient(circle at top left, #fed7aa 0, transparent 28%),
    radial-gradient(circle at top right, #fde68a 0, transparent 24%),
    var(--bg);
  color: var(--text);
  line-height: 1.7;
}
a { color: var(--primary-dark); font-weight: 800; text-decoration: none; }
a:hover { text-decoration: underline; }
.topbar {
  position: sticky;
  top: 0;
  z-index: 10;
  background: rgba(255, 247, 237, 0.94);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--line);
}
.topbar-inner {
  max-width: 1240px;
  margin: auto;
  padding: 14px 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
}
.brand {
  display: flex;
  align-items: center;
  gap: 12px;
  font-weight: 900;
  color: var(--primary-dark);
  line-height: 1.25;
}
.brand-icon {
  width: 44px;
  height: 44px;
  border-radius: 15px;
  background: linear-gradient(135deg, var(--primary), var(--accent));
  display: grid;
  place-items: center;
  color: white;
  font-weight: 900;
  box-shadow: 0 10px 22px rgba(217, 119, 6, 0.28);
}
.nav {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  justify-content: flex-end;
}
.nav a {
  font-size: 14px;
  padding: 8px 12px;
  border: 1px solid var(--line);
  border-radius: 999px;
  background: #fff;
  color: var(--primary-dark);
}
.hero { max-width: 1240px; margin: 0 auto; padding: 56px 20px 28px; }
.hero-card {
  background: linear-gradient(135deg, #fff, #ffedd5);
  border: 1px solid var(--line);
  border-radius: 34px;
  box-shadow: var(--shadow);
  padding: 44px;
  overflow: hidden;
  position: relative;
}
.badge {
  display: inline-flex;
  background: #fff7ed;
  border: 1px solid var(--line);
  color: var(--primary-dark);
  padding: 8px 14px;
  border-radius: 999px;
  font-weight: 800;
  margin-bottom: 18px;
}
h1 {
  font-size: clamp(34px, 6vw, 64px);
  line-height: 1.05;
  margin: 0 0 18px;
  color: var(--primary-dark);
  max-width: 950px;
}
.hero p { max-width: 900px; font-size: 20px; color: var(--muted); margin: 0 0 24px; }
.hero-actions { display: flex; flex-wrap: wrap; gap: 14px; margin-top: 24px; }
.btn {
  border: 0;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 13px 18px;
  border-radius: 16px;
  font-weight: 900;
  font-size: 15px;
  text-decoration: none;
}
.btn-primary { background: var(--primary); color: #fff; box-shadow: 0 12px 24px rgba(217, 119, 6, 0.25); }
.btn-secondary { background: #fff; color: var(--primary-dark); border: 1px solid var(--line); }
.container {
  max-width: 1240px;
  margin: auto;
  padding: 22px 20px 70px;
  display: grid;
  grid-template-columns: 310px 1fr;
  gap: 24px;
  align-items: start;
}
.sidebar {
  position: sticky;
  top: 86px;
  background: rgba(255, 255, 255, 0.86);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px;
  box-shadow: var(--shadow);
  max-height: calc(100vh - 110px);
  overflow: auto;
}
.sidebar h3 { margin: 0 0 12px; color: var(--primary-dark); }
.sidebar a {
  display: block;
  padding: 9px 10px;
  border-radius: 12px;
  color: var(--muted);
  font-weight: 700;
  font-size: 14px;
}
.sidebar a:hover { background: var(--soft); text-decoration: none; color: var(--primary-dark); }
.content { display: grid; gap: 22px; }
section.lesson {
  background: rgba(255, 255, 255, 0.92);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 28px;
  box-shadow: var(--shadow);
}
section.lesson h2 { margin: 0 0 12px; color: var(--primary-dark); font-size: 30px; line-height: 1.2; }
section.lesson h3 { margin-top: 24px; color: var(--primary-dark); }
.note, .success, .warning, .info {
  padding: 16px 18px;
  border-radius: 16px;
  margin: 18px 0;
}
.note { background: #fffbeb; border-left: 5px solid var(--accent); }
.success { background: #f0fdf4; border-left: 5px solid var(--success); }
.warning { background: #fef2f2; border-left: 5px solid var(--danger); }
.info { background: #f0f9ff; border-left: 5px solid var(--info); }
pre {
  position: relative;
  background: var(--code-bg);
  color: var(--code-text);
  padding: 46px 18px 18px;
  border-radius: 18px;
  overflow-x: auto;
  border: 1px solid #3b220f;
  box-shadow: inset 0 0 0 1px rgba(255,255,255,.04);
}
code { font-family: Consolas, Monaco, "Courier New", monospace; font-size: 14px; }
.copy-btn {
  position: absolute;
  top: 10px;
  right: 10px;
  border: 1px solid rgba(255,255,255,.2);
  background: rgba(255,255,255,.08);
  color: #fff;
  border-radius: 10px;
  padding: 6px 9px;
  cursor: pointer;
  font-weight: 800;
  font-size: 12px;
}
.copy-btn:hover { background: rgba(255,255,255,.16); }
.table-wrap {
  overflow-x: auto;
  border-radius: 18px;
  border: 1px solid var(--line);
  margin-top: 16px;
}
table { width: 100%; border-collapse: collapse; background: white; min-width: 850px; }
th, td { padding: 14px; border-bottom: 1px solid var(--line); text-align: left; vertical-align: top; }
th { background: var(--soft); color: var(--primary-dark); }
.cards { display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; margin-top: 18px; }
.card { background: #fff7ed; border: 1px solid var(--line); border-radius: 18px; padding: 16px; }
.card strong { color: var(--primary-dark); display: block; margin-bottom: 6px; }
.diagram {
  background: #fffaf3;
  border: 1px solid var(--line);
  border-radius: 24px;
  padding: 18px;
  margin: 22px 0;
  overflow-x: auto;
}
.diagram svg { width: 100%; min-width: 760px; height: auto; display: block; }
.speak-tag-label {
  display: inline-flex;
  margin-bottom: 10px;
  padding: 5px 10px;
  border-radius: 999px;
  background: #fff7ed;
  border: 1px solid #fed7aa;
  color: #92400e;
  font-size: 12px;
  font-weight: 900;
}
.checkpoint {
  margin-top: 22px;
  padding: 18px;
  border-radius: 20px;
  border: 1px solid #fed7aa;
  background: linear-gradient(135deg, #fff7ed, #fffbeb);
  box-shadow: 0 12px 26px rgba(120, 53, 15, 0.08);
}
.checkpoint h3 { margin: 0 0 10px; color: #92400e; font-size: 20px; }
.checkpoint-list { display: grid; gap: 9px; margin-top: 12px; }
.checkpoint-list label {
  display: flex;
  gap: 10px;
  align-items: flex-start;
  background: #fff;
  border: 1px solid #fed7aa;
  border-radius: 14px;
  padding: 10px 12px;
  font-weight: 700;
  color: var(--muted);
}
.checkpoint-list input { margin-top: 5px; transform: scale(1.2); accent-color: #d97706; }
.checkpoint-continue {
  margin-top: 14px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border: 0;
  border-radius: 14px;
  padding: 10px 14px;
  background: #d97706;
  color: white;
  font-weight: 900;
  cursor: pointer;
}
.checkpoint-continue:disabled { opacity: 0.45; cursor: not-allowed; }
.checkpoint-status { margin-top: 10px; font-size: 14px; color: #7c5b35; font-weight: 800; }
.footer { max-width: 1240px; margin: 0 auto 36px; padding: 24px 20px; color: var(--muted); text-align: center; }
@media (max-width: 980px) {
  .container { grid-template-columns: 1fr; }
  .sidebar { position: static; max-height: none; }
  .cards { grid-template-columns: 1fr; }
  .hero-card { padding: 28px; }
}
@media print {
  .topbar, .sidebar, .hero-actions, .copy-btn, .checkpoint-continue { display: none; }
  body { background: white; }
  .container { display: block; }
  section.lesson, .hero-card { box-shadow: none; break-inside: avoid; }
}