:root {
  --bg: #0d0e0f;
  --surface: #151617;
  --surface-2: #1d1e1f;
  --border: #333435;
  --text: #e8e8e8;
  --muted: #9a9b9d;
  --teal: #4ec9b0;
  --green: #4ecb71;
  --coral: #ff6b6b;
  --gold: #ffd700;
  --radius: 18px;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; }

body {
  font-family: "Inter", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}

a { color: var(--teal); text-decoration: none; }
a:hover { text-decoration: underline; }

.container { max-width: 1140px; margin: 0 auto; padding: 0 22px; }

/* ---------- Nav ---------- */
.nav {
  position: sticky; top: 0; z-index: 50;
  background: rgba(13, 14, 15, .82);
  backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--border);
}
.nav-inner {
  max-width: 1140px; margin: 0 auto; padding: 0 22px;
  height: 64px; display: flex; align-items: center; gap: 26px;
}
.brand { display: flex; align-items: center; gap: 10px; color: var(--text); font-weight: 800; font-size: 18px; }
.brand:hover { text-decoration: none; }
.brand-logo {
  width: 30px; height: 30px; border-radius: 9px; display: flex; align-items: center; justify-content: center;
  background: linear-gradient(135deg, var(--teal), var(--coral)); color: #0d0e0f; font-weight: 900; font-size: 15px;
}
.nav-links { display: flex; gap: 6px; margin-left: auto; align-items: center; }
.nav-links a { color: var(--muted); font-size: 14px; padding: 8px 13px; border-radius: 10px; }
.nav-links a:hover { color: var(--text); background: var(--surface-2); text-decoration: none; }
.nav-cta {
  background: var(--text); color: #0d0e0f; font-weight: 700; border-radius: 10px; padding: 9px 16px; font-size: 14px;
}
.nav-cta:hover { background: var(--teal); color: #0d0e0f; text-decoration: none; }

/* ---------- Hero ---------- */
.hero { padding: 96px 0 72px; text-align: center; position: relative; overflow: hidden; }
.hero::before {
  content: ""; position: absolute; inset: 0; pointer-events: none;
  background:
    radial-gradient(600px 300px at 20% 10%, rgba(78, 201, 176, .14), transparent 60%),
    radial-gradient(600px 300px at 80% 20%, rgba(255, 107, 107, .12), transparent 60%),
    radial-gradient(700px 400px at 50% 100%, rgba(255, 215, 0, .08), transparent 60%);
}
.hero-inner { position: relative; max-width: 780px; margin: 0 auto; }
.hero-badge {
  display: inline-block; border: 1px solid var(--border); background: var(--surface);
  color: var(--muted); font-size: 13px; border-radius: 999px; padding: 6px 14px; margin-bottom: 22px;
}
.hero h1 { font-size: clamp(38px, 6vw, 64px); font-weight: 800; line-height: 1.15; letter-spacing: -1px; margin-bottom: 20px; }
.hero h1 .grad {
  background: linear-gradient(90deg, var(--teal), var(--gold));
  -webkit-background-clip: text; background-clip: text; color: transparent;
}
.hero p { font-size: 18px; color: var(--muted); max-width: 620px; margin: 0 auto 32px; }
.hero-cta { display: flex; gap: 14px; justify-content: center; flex-wrap: wrap; }
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  border: 1px solid var(--border); background: var(--surface-2); color: var(--text);
  border-radius: 12px; padding: 13px 24px; font-size: 15px; font-weight: 600; cursor: pointer;
  transition: transform .12s, border-color .12s, background .12s;
}
.btn:hover { transform: translateY(-1px); text-decoration: none; }
.btn-primary { background: var(--text); color: #0d0e0f; border-color: var(--text); font-weight: 700; }
.btn-primary:hover { background: var(--teal); border-color: var(--teal); }
.btn-outline:hover { border-color: var(--teal); color: var(--teal); }

/* ---------- Sections ---------- */
.section { padding: 64px 0; border-top: 1px solid var(--border); }
.section-head { max-width: 640px; margin-bottom: 40px; }
.section-head h2 { font-size: 30px; font-weight: 800; letter-spacing: -0.5px; margin-bottom: 10px; }
.section-head p { color: var(--muted); font-size: 15px; }

/* ---------- Course grid ---------- */
.course-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 14px; }
.course-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 22px; display: flex; flex-direction: column; gap: 10px; transition: border-color .15s, transform .15s;
}
.course-card:hover { border-color: var(--teal); transform: translateY(-2px); }
.course-card .tag {
  display: inline-block; align-self: flex-start; font-size: 11px; font-weight: 700;
  border-radius: 999px; padding: 3px 10px;
}
.tag-live { background: rgba(78, 203, 113, .14); color: var(--green); border: 1px solid rgba(78, 203, 113, .4); }
.tag-soon { background: rgba(255, 215, 0, .1); color: var(--gold); border: 1px solid rgba(255, 215, 0, .35); }
.tag-plan { background: var(--surface-2); color: var(--muted); border: 1px solid var(--border); }
.course-card h3 { font-size: 17px; font-weight: 700; }
.course-card p { font-size: 13px; color: var(--muted); flex: 1; }
.course-card .go { font-size: 13px; font-weight: 600; }
.course-card.live .go { color: var(--teal); }
.course-card:not(.live) .go { color: var(--muted); cursor: default; }

/* ---------- Features ---------- */
.feat-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; }
.feat-card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 24px;
}
.feat-card .ico { font-size: 26px; margin-bottom: 12px; }
.feat-card h3 { font-size: 16px; font-weight: 700; margin-bottom: 6px; }
.feat-card p { font-size: 14px; color: var(--muted); }

/* ---------- About / footer ---------- */
.about-page { max-width: 760px; margin: 0 auto; padding: 56px 22px 80px; }
.about-page h1 { font-size: 32px; font-weight: 800; margin-bottom: 6px; }
.about-page .sub { color: var(--muted); margin-bottom: 32px; }
.about-block { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 26px; margin-bottom: 18px; }
.about-block h2 { font-size: 19px; font-weight: 700; margin-bottom: 10px; padding-bottom: 10px; border-bottom: 1px solid var(--border); }
.about-block h3 { font-size: 15px; font-weight: 700; margin: 16px 0 6px; color: var(--teal); }
.about-block p, .about-block li { font-size: 14px; color: var(--muted); }
.about-block ul { margin: 8px 0 0 18px; }

.footer { border-top: 1px solid var(--border); padding: 40px 0; }
.footer-inner { max-width: 1140px; margin: 0 auto; padding: 0 22px; display: flex; justify-content: space-between; gap: 20px; flex-wrap: wrap; }
.footer .f-brand { font-weight: 800; margin-bottom: 6px; }
.footer .muted { color: var(--muted); font-size: 13px; }
.footer-links { display: flex; gap: 18px; font-size: 13px; }

@media (max-width: 960px) {
  .course-grid { grid-template-columns: repeat(2, 1fr); }
  .feat-grid { grid-template-columns: 1fr; }
}
@media (max-width: 640px) {
  .course-grid { grid-template-columns: 1fr; }
  .nav-inner { gap: 12px; }
  .nav-links a { padding: 6px 9px; }
  .hero { padding: 64px 0 48px; }
}