:root {
  --bg: #0b1020;
  --bg-card: #131b33;
  --bg-card-hover: #182347;
  --text: #e8eefc;
  --text-muted: #8aa0c7;
  --accent: #5b8cff;
  --accent-2: #6bd6ff;
  --border: rgba(255,255,255,0.08);
  --error: #ff5b8c;
  --success: #4ade80;
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; min-height: 100%; }
body {
  font-family: -apple-system, BlinkMacSystemFont, "Inter", "Segoe UI", Roboto, sans-serif;
  background: radial-gradient(1200px 600px at 50% -10%, #1a2547 0%, #0b1020 60%) fixed;
  color: var(--text);
  -webkit-font-smoothing: antialiased;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
  border-bottom: 1px solid var(--border);
  flex-wrap: wrap;
  gap: 12px;
}
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; color: var(--text); font-weight: 600; }
.brand b { color: var(--accent-2); }
.logo {
  width: 32px; height: 32px;
  border-radius: 9px;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  display: grid; place-items: center;
  font-weight: 700; color: #0b1020; font-size: 13px;
}
nav { display: flex; gap: 18px; align-items: center; }
nav a { color: var(--text-muted); text-decoration: none; font-size: 15px; }
nav a:hover { color: var(--text); }

.container { max-width: 1100px; margin: 0 auto; padding: 36px 24px 60px; }
.footer { padding: 24px; text-align: center; color: var(--text-muted); font-size: 13px; border-top: 1px solid var(--border); margin-top: 60px; }

h1 { font-size: 36px; letter-spacing: -0.02em; line-height: 1.1; margin: 0 0 16px; }
h2 { font-size: 24px; margin: 24px 0 12px; }
h3 { font-size: 18px; margin: 16px 0 8px; }
p { line-height: 1.55; }
a { color: var(--accent-2); }

.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 22px;
  margin-bottom: 16px;
}

.grid { display: grid; gap: 16px; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); }
.course-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 20px;
  text-decoration: none;
  color: var(--text);
  display: block;
  transition: transform 0.12s ease, background 0.12s ease;
}
.course-card:hover { background: var(--bg-card-hover); transform: translateY(-2px); }
.course-card h3 { margin: 0 0 6px; }
.course-card .meta { color: var(--text-muted); font-size: 13px; margin-top: 8px; }
.progress-bar { height: 6px; background: rgba(255,255,255,0.08); border-radius: 3px; overflow: hidden; margin-top: 12px; }
.progress-bar > div { height: 100%; background: linear-gradient(90deg, var(--accent), var(--accent-2)); }

.form { max-width: 420px; margin: 30px auto; }
.form label { display: block; font-size: 14px; color: var(--text-muted); margin: 14px 0 6px; }
.form input, .form textarea, .form select {
  width: 100%;
  background: rgba(0,0,0,0.25);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 12px 14px;
  color: var(--text);
  font-size: 15px;
  font-family: inherit;
}
.form input:focus, .form textarea:focus, .form select:focus {
  outline: none;
  border-color: var(--accent);
}
.btn {
  display: inline-block;
  padding: 12px 22px;
  border-radius: 10px;
  background: linear-gradient(135deg, var(--accent), var(--accent-2));
  color: #0b1020;
  font-weight: 600;
  text-decoration: none;
  border: none;
  cursor: pointer;
  font-size: 15px;
  font-family: inherit;
}
.btn:hover { filter: brightness(1.08); }
.btn-ghost { background: transparent; border: 1px solid var(--border); color: var(--text); }
.btn-ghost:hover { background: rgba(255,255,255,0.04); }
.btn-block { display: block; width: 100%; text-align: center; margin-top: 18px; }

.alert { padding: 12px 14px; border-radius: 10px; margin: 14px 0; font-size: 14px; }
.alert-error { background: rgba(255,91,140,0.12); border: 1px solid rgba(255,91,140,0.3); color: #ffb3c7; }
.alert-success { background: rgba(74,222,128,0.12); border: 1px solid rgba(74,222,128,0.3); color: #b8f5cd; }
.alert-info { background: rgba(91,140,255,0.12); border: 1px solid rgba(91,140,255,0.3); color: #c1d3ff; }

.lesson-layout { display: grid; grid-template-columns: 300px 1fr; gap: 24px; }
@media (max-width: 880px) { .lesson-layout { grid-template-columns: 1fr; } }
.sidebar { background: var(--bg-card); border: 1px solid var(--border); border-radius: 14px; padding: 16px; height: fit-content; }
.sidebar .module-title { font-weight: 600; margin-top: 10px; margin-bottom: 6px; color: var(--text-muted); font-size: 13px; text-transform: uppercase; letter-spacing: 0.05em; }
.sidebar .lesson-link { display: flex; gap: 8px; align-items: center; padding: 8px 10px; border-radius: 8px; text-decoration: none; color: var(--text); font-size: 14px; }
.sidebar .lesson-link:hover { background: rgba(255,255,255,0.04); }
.sidebar .lesson-link.active { background: rgba(91,140,255,0.15); color: var(--accent-2); }
.sidebar .lesson-link.locked { color: var(--text-muted); }
.sidebar .lesson-link.done { color: var(--success); }

.video-wrap { position: relative; padding-bottom: 56.25%; height: 0; border-radius: 12px; overflow: hidden; background: #000; }
.video-wrap iframe { position: absolute; top: 0; left: 0; width: 100%; height: 100%; border: 0; }

.muted { color: var(--text-muted); }
.tag { display: inline-block; padding: 3px 10px; border-radius: 999px; background: rgba(91,140,255,0.15); color: var(--accent-2); font-size: 12px; }
.tag-locked { background: rgba(255,255,255,0.06); color: var(--text-muted); }
.tag-preview { background: rgba(74,222,128,0.15); color: var(--success); }

table { width: 100%; border-collapse: collapse; }
th, td { padding: 10px 12px; text-align: left; border-bottom: 1px solid var(--border); font-size: 14px; }
th { color: var(--text-muted); font-weight: 500; }