:root {
  color-scheme: light;
  --ink: #17212f;
  --muted: #5f6b78;
  --paper: #fffaf0;
  --cream: #f5f1e6;
  --line: rgba(23, 33, 47, 0.14);
  --green: #2f9b6b;
  --blue: #477fd3;
  --red: #e4572e;
  --gold: #eab94f;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  background:
    radial-gradient(circle at 15% 8%, rgba(234, 185, 79, 0.16), transparent 26%),
    linear-gradient(180deg, #f7f4ea 0%, #fffaf0 45%, #f1f5ef 100%);
  font-family: "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
}

a {
  color: inherit;
}

.lesson-shell {
  width: min(1180px, calc(100% - 32px));
  margin: 0 auto;
  padding: 24px 0 56px;
}

.site-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 18px;
  padding: 16px 0 28px;
}

.site-brand {
  font-weight: 900;
  text-decoration: none;
}

.site-nav {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
  font-size: 14px;
  color: var(--muted);
}

.site-nav a {
  text-decoration: none;
  border-bottom: 1px solid transparent;
}

.site-nav a:hover {
  border-bottom-color: currentColor;
}

.hero {
  display: grid;
  grid-template-columns: 0.95fr 1.25fr;
  gap: 30px;
  align-items: center;
  padding: 34px;
  border: 1px solid var(--line);
  border-radius: 26px;
  background: rgba(255, 255, 255, 0.7);
  box-shadow: 0 22px 60px rgba(49, 55, 66, 0.12);
}

.eyebrow {
  margin: 0 0 12px;
  color: var(--red);
  font-size: 13px;
  font-weight: 900;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1 {
  margin: 0;
  font-size: clamp(34px, 5vw, 58px);
  line-height: 1.05;
  letter-spacing: 0;
}

.hero-copy {
  margin: 18px 0 0;
  color: var(--muted);
  font-size: 18px;
  line-height: 1.7;
}

.hero-meta {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 22px;
}

.hero-meta span {
  padding: 9px 12px;
  border-radius: 999px;
  background: var(--paper);
  border: 1px solid var(--line);
  font-size: 14px;
  font-weight: 800;
}

.video-frame {
  position: relative;
  overflow: hidden;
  border: 8px solid #ffffff;
  border-radius: 24px;
  background: #101820;
  box-shadow: 0 18px 48px rgba(23, 33, 47, 0.2);
}

.video-frame video {
  display: block;
  width: 100%;
  aspect-ratio: 16 / 9;
  background: #101820;
}

.video-note {
  margin: 14px 0 0;
  color: var(--muted);
  font-size: 14px;
  line-height: 1.6;
}

.section {
  margin-top: 30px;
  padding: 30px;
  border: 1px solid var(--line);
  border-radius: 24px;
  background: rgba(255, 255, 255, 0.72);
}

.section h2 {
  margin: 0 0 18px;
  font-size: 30px;
  letter-spacing: 0;
}

.grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 16px;
}

.card {
  min-height: 150px;
  padding: 20px;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: var(--paper);
}

.card span {
  display: inline-block;
  margin-bottom: 10px;
  color: var(--blue);
  font-size: 13px;
  font-weight: 900;
}

.card h3 {
  margin: 0 0 10px;
  font-size: 20px;
}

.card p,
.section li {
  color: var(--muted);
  line-height: 1.65;
}

.section ul {
  margin: 0;
  padding-left: 20px;
}

.catalog-hero {
  grid-template-columns: 1fr;
}

.catalog-note {
  max-width: 760px;
}

.lesson-list {
  display: grid;
  gap: 14px;
}

.lesson-row {
  display: grid;
  grid-template-columns: auto 1fr auto;
  gap: 18px;
  align-items: center;
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 18px;
  background: var(--paper);
  text-decoration: none;
}

.lesson-row.locked {
  color: var(--muted);
  background: rgba(255, 255, 255, 0.62);
}

.lesson-number {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 54px;
  height: 54px;
  border-radius: 50%;
  color: #ffffff;
  background: var(--ink);
  font-weight: 900;
}

.lesson-row.locked .lesson-number {
  color: var(--ink);
  background: #ffffff;
  border: 1px solid var(--line);
}

.lesson-row h3 {
  margin: 0 0 6px;
  font-size: 22px;
}

.lesson-row p {
  margin: 0;
  color: var(--muted);
  line-height: 1.6;
}

.lesson-status {
  padding: 9px 12px;
  border-radius: 999px;
  color: #ffffff;
  background: var(--green);
  font-size: 14px;
  font-weight: 900;
  white-space: nowrap;
}

.lesson-row.locked .lesson-status {
  color: var(--muted);
  background: #ffffff;
  border: 1px solid var(--line);
}

.lesson-actions {
  display: flex;
  gap: 14px;
  flex-wrap: wrap;
  margin-top: 28px;
}

.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 46px;
  padding: 0 18px;
  border-radius: 999px;
  text-decoration: none;
  font-weight: 900;
}

.button.primary {
  color: white;
  background: var(--ink);
}

.button.secondary {
  background: #ffffff;
  border: 1px solid var(--line);
}

.footer {
  padding: 34px 0 0;
  color: var(--muted);
  font-size: 14px;
  text-align: center;
}

@media (max-width: 820px) {
  .site-header,
  .hero {
    grid-template-columns: 1fr;
  }

  .hero {
    padding: 22px;
  }

  .grid {
    grid-template-columns: 1fr;
  }

  .lesson-row {
    grid-template-columns: 1fr;
  }

  .lesson-number {
    width: 46px;
    height: 46px;
  }

  .lesson-status {
    width: fit-content;
  }
}