:root {
  --primary: #1d2470;
  --secondary: #2e3a9e;
  --accent: #f4b41a;
  --bg: #f4f6fb;
  --surface: #ffffff;
  --text: #1c2140;
  --muted: #5d6684;
  --line: #e2e6f2;
  --ok: #1f7a4d;
  --danger: #9b2c2c;
  --warn: #8a5a00;
  --shadow: 0 10px 30px rgba(29, 36, 112, 0.08);
  --radius: 14px;
  --space: 16px;
  --max: 1080px;
  --font: "Segoe UI", "Helvetica Neue", Arial, sans-serif;
}

* { box-sizing: border-box; }
html { overflow-x: hidden; }
body {
  margin: 0;
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.5;
  color: var(--text);
  background: var(--bg);
}
img, video { max-width: 100%; height: auto; }
a { color: var(--secondary); }
h1, h2, h3 { line-height: 1.25; margin: 0 0 8px; }
h1 { font-size: 1.75rem; }
h2 { font-size: 1.25rem; }
p { margin: 0 0 12px; }

.wrap { width: min(var(--max), calc(100% - 32px)); margin: 24px auto 48px; }
.site-header, .site-footer {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 14px 16px;
  background: var(--primary);
  color: #fff;
}
.site-header { position: sticky; top: 0; z-index: 10; flex-wrap: wrap; }
.brand { color: #fff; font-weight: 800; text-decoration: none; letter-spacing: 0.04em; }
.site-nav { display: none; width: 100%; flex-direction: column; gap: 8px; }
.site-nav.open { display: flex; }
.site-nav a { color: #fff; text-decoration: none; padding: 8px 0; }
.nav-accent { color: var(--accent) !important; }
.nav-toggle {
  margin-left: auto;
  background: transparent;
  color: #fff;
  border: 1px solid rgba(255,255,255,.4);
  border-radius: 8px;
  padding: 6px 10px;
}
.site-footer { justify-content: space-between; flex-wrap: wrap; }
.site-footer span { color: var(--accent); }

.hero {
  background: linear-gradient(160deg, var(--primary), var(--secondary));
  color: #fff;
  border-radius: var(--radius);
  padding: 28px 22px;
  margin-bottom: 22px;
}
.hero p { max-width: 40rem; }
.grid { display: grid; gap: 16px; }
.cards { grid-template-columns: 1fr; }
.card, .panel {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 16px;
}
.card h2 { font-size: 1.1rem; }
.muted { color: var(--muted); }
.price { color: var(--primary); font-weight: 700; }

.btn, button, input, select, textarea { font: inherit; }
.btn {
  display: inline-block;
  border: 0;
  border-radius: 10px;
  padding: 10px 14px;
  background: var(--primary);
  color: #fff;
  text-decoration: none;
  cursor: pointer;
}
.btn.secondary { background: var(--secondary); }
.btn.accent { background: var(--accent); color: var(--primary); }
.btn.ghost { background: transparent; color: var(--primary); border: 1px solid var(--line); }
.btn.danger { background: var(--danger); }
.btn.small { padding: 6px 10px; font-size: 0.9rem; }
.actions { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }

label { display: block; font-weight: 600; margin: 12px 0 6px; }
input, select, textarea {
  width: 100%;
  max-width: 100%;
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 10px 12px;
  background: #fff;
  color: var(--text);
}
textarea { min-height: 120px; resize: vertical; }
.form-row { margin-bottom: 8px; }

.alert { border-radius: 10px; padding: 12px 14px; margin-bottom: 16px; }
.alert-info { background: #e8ebfa; color: var(--primary); }
.alert-ok { background: #e5f6ee; color: var(--ok); }
.alert-bad { background: #fdecec; color: var(--danger); }

.badge {
  display: inline-block;
  border-radius: 999px;
  padding: 2px 8px;
  background: #e8ebfa;
  color: var(--primary);
  font-size: 0.8rem;
  font-weight: 700;
}
.badge.warn { background: #fff4d6; color: var(--warn); }
.badge.ok { background: #e5f6ee; color: var(--ok); }
.badge.bad { background: #fdecec; color: var(--danger); }

.progress { height: 10px; background: #e6e9f5; border-radius: 999px; overflow: hidden; }
.progress > span { display: block; height: 100%; background: var(--accent); }

.table-scroll { overflow-x: auto; }
table { width: 100%; border-collapse: collapse; }
th, td { text-align: left; padding: 10px 8px; border-bottom: 1px solid var(--line); vertical-align: top; }
th { font-size: 0.85rem; color: var(--muted); }

.empty { padding: 28px 8px; text-align: center; }
.tabs { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 16px; }
.tabs a { text-decoration: none; padding: 8px 12px; border-radius: 999px; background: #fff; border: 1px solid var(--line); color: var(--primary); }
.tabs a.active { background: var(--primary); color: #fff; }

.classroom { display: grid; gap: 16px; }
.lesson-nav a { display: block; padding: 8px 0; text-decoration: none; border-bottom: 1px solid var(--line); }
.lesson-nav a.active { font-weight: 700; color: var(--primary); }
.prose p { margin-bottom: 12px; }
.stack { display: grid; gap: 12px; }

dialog {
  border: 0;
  border-radius: var(--radius);
  padding: 16px;
  width: min(480px, calc(100% - 24px));
  box-shadow: var(--shadow);
}
dialog::backdrop { background: rgba(29, 36, 112, 0.45); }

@media (min-width: 800px) {
  .nav-toggle { display: none; }
  .site-nav { display: flex; width: auto; flex-direction: row; align-items: center; margin-left: auto; gap: 16px; }
  .cards { grid-template-columns: repeat(3, 1fr); }
  .classroom { grid-template-columns: 280px 1fr; align-items: start; }
  .split { display: grid; grid-template-columns: 1.2fr .8fr; gap: 16px; }
}