* { margin: 0; padding: 0; box-sizing: border-box; }
body {
  font-family: "Microsoft YaHei", "PingFang SC", sans-serif;
  background: #ffffff;
  color: #1f2937;
  min-height: 100vh;
  display: flex;
}
.home-body { display: block; }
.site-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 18px 32px; border-bottom: 1px solid #f1f3f7;
}
.header-right { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; justify-content: flex-end; }
.badge-link {
  display: inline-block; text-decoration: none;
  background: linear-gradient(135deg, #6366f1, #8b5cf6); color: #fff;
  padding: 7px 16px; border-radius: 999px; font-size: 13px; font-weight: 600;
  transition: opacity .15s, transform .15s;
}
.badge-link:hover { opacity: .88; transform: translateY(-1px); }
.home-hero {
  text-align: center; padding: 60px 24px 30px;
  background: linear-gradient(180deg, #f8faff, #ffffff);
}
.home-hero h1 { font-size: 34px; color: #111827; }
.home-hero p { color: #6b7280; margin-top: 12px; line-height: 1.8; max-width: 640px; margin-left: auto; margin-right: auto; }
.home-main { max-width: 1000px; margin: 0 auto; padding: 30px 24px 40px; }
.section-title { font-size: 20px; color: #111827; margin-bottom: 16px; }
.series-cards { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 18px; }
.series-card {
  background: #fff; border: 1px solid #eef0f4; border-radius: 16px; overflow: hidden;
  transition: transform .15s, box-shadow .15s;
}
.series-card:hover:not(.disabled) { transform: translateY(-3px); box-shadow: 0 8px 24px rgba(0,0,0,0.07); }
.series-card.disabled { opacity: 0.72; }
.series-card .cover { width: 100%; aspect-ratio: 16/9; object-fit: cover; display: block; background: #f1f3f7; }
.series-card .body { padding: 18px; }
.series-card .status {
  font-size: 12px; color: #16a34a; background: #f0fdf4;
  padding: 3px 12px; border-radius: 999px; display: inline-block;
}
.series-card.disabled .status { color: #9ca3af; background: #f3f4f6; }
.series-card h3 { margin: 10px 0 8px; font-size: 19px; color: #111827; }
.series-card p { font-size: 13px; color: #6b7280; line-height: 1.7; min-height: 60px; }
.cta-btn {
  display: inline-block; margin-top: 14px; text-decoration: none;
  background: linear-gradient(135deg, #22d3ee, #06b6d4); color: #062b33;
  padding: 10px 22px; border-radius: 999px; font-size: 14px; font-weight: 700;
}
.cta-btn.disabled { background: #e5e7eb; color: #9ca3af; cursor: not-allowed; }
.home-features { margin-top: 40px; }
.home-features h2 { font-size: 20px; color: #111827; margin-bottom: 16px; }
.feature-list { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 16px; }
.feature { background: #f8fafc; border: 1px solid #f1f3f7; border-radius: 14px; padding: 18px; }
.feature b { color: #4f46e5; font-size: 15px; }
.feature p { color: #6b7280; font-size: 13px; margin-top: 6px; line-height: 1.6; }
.sidebar {
  width: 272px;
  flex-shrink: 0;
  background: linear-gradient(180deg, #ffffff, #f8fafc);
  border-right: 1px solid #eef0f4;
  padding: 22px 16px;
  position: sticky;
  top: 0;
  height: 100vh;
  overflow-y: auto;
}
.brand { display: flex; align-items: center; gap: 10px; margin-bottom: 22px; }
.brand-logo {
  width: 42px; height: 42px; border-radius: 12px;
  background: linear-gradient(135deg, #22d3ee, #6366f1);
  color: #fff; font-size: 20px; font-weight: 800;
  display: flex; align-items: center; justify-content: center;
}
.brand-name { font-size: 17px; font-weight: 800; color: #111827; }
.brand-sub { font-size: 12px; color: #9ca3af; margin-top: 2px; }
.series-item {
  border: 1px solid #eef0f4; border-radius: 14px; padding: 12px; margin-bottom: 12px;
  background: #fff;
}
.series-item.active { border-color: #c7d2fe; box-shadow: 0 2px 10px rgba(99,102,241,0.08); }
.series-item.coming { opacity: 0.75; background: #fafafa; }
.series-title { font-size: 14px; font-weight: 700; color: #111827; }
.series-meta { font-size: 12px; color: #9ca3af; margin: 2px 0 10px; }
.lesson-list { list-style: none; }
.lesson-list li {
  display: flex; align-items: center; gap: 8px;
  padding: 8px 10px; border-radius: 9px; cursor: pointer;
  font-size: 13px; color: #4b5563; transition: background .15s;
}
.lesson-list li:hover { background: #f3f4f6; }
.lesson-list li.current { background: #eef2ff; color: #4f46e5; font-weight: 600; }
.lesson-list li .num {
  width: 22px; height: 22px; border-radius: 50%;
  background: #f3f4f6; color: #6b7280; font-size: 11px; font-weight: 700;
  display: flex; align-items: center; justify-content: center; flex-shrink: 0;
}
.lesson-list li.current .num { background: #6366f1; color: #fff; }
.main { flex: 1; min-width: 0; padding: 0 30px 40px; }
.topbar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 18px 0; border-bottom: 1px solid #f1f3f7;
}
nav.crumbs { display: flex; gap: 16px; }
.crumb { font-size: 13px; color: #9ca3af; text-decoration: none; }
.crumb:hover { color: #4f46e5; }
.badge {
  background: linear-gradient(135deg, #6366f1, #8b5cf6); color: #fff;
  padding: 4px 14px; border-radius: 999px; font-size: 12px; font-weight: 600;
}
.hero { padding: 34px 0 10px; }
.hero h1 { font-size: 30px; color: #111827; letter-spacing: 0.5px; }
.hero p { color: #6b7280; margin-top: 10px; line-height: 1.7; max-width: 720px; }
.hero-tags { display: flex; gap: 8px; margin-top: 14px; flex-wrap: wrap; }
.hero-tags span {
  font-size: 12px; color: #4f46e5; background: #eef2ff;
  padding: 4px 12px; border-radius: 999px;
}
.course-intro { margin: 20px 0 8px; }
.course-intro h2 { font-size: 18px; color: #111827; margin-bottom: 10px; }
.intro-list { list-style: none; }
.intro-list li {
  position: relative; padding-left: 22px; color: #4b5563; font-size: 14px;
  line-height: 1.8;
}
.intro-list li::before {
  content: ""; position: absolute; left: 4px; top: 11px;
  width: 8px; height: 8px; border-radius: 50%; background: #6366f1;
}
.grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 18px; margin-top: 18px; }
.card {
  background: #fff; border: 1px solid #eef0f4; border-radius: 14px; overflow: hidden;
  cursor: pointer; transition: transform .15s, box-shadow .15s;
}
.card:hover { transform: translateY(-3px); box-shadow: 0 8px 24px rgba(0,0,0,0.07); }
.card .cover { width: 100%; aspect-ratio: 16/9; object-fit: cover; display: block; background: #f1f3f7; }
.card .body { padding: 14px 16px; }
.card .no { font-size: 12px; color: #6366f1; font-weight: 700; }
.card h3 { margin: 4px 0 6px; font-size: 16px; color: #111827; }
.card p { font-size: 13px; color: #6b7280; line-height: 1.5; }
.card .meta { display: flex; align-items: center; justify-content: space-between; margin-top: 10px; }
.card .dur { font-size: 12px; color: #9ca3af; }
.play {
  background: linear-gradient(135deg, #22d3ee, #06b6d4); color: #062b33;
  border: none; padding: 6px 16px; border-radius: 999px; font-size: 13px; font-weight: 700; cursor: pointer;
}
.detail {
  margin-top: 26px; background: #fff; border: 1px solid #eef0f4;
  border-radius: 16px; padding: 22px; box-shadow: 0 4px 20px rgba(0,0,0,0.04);
}
.detail-head { display: flex; align-items: center; justify-content: space-between; gap: 12px; flex-wrap: wrap; }
.detail-head h2 { color: #111827; font-size: 20px; }
.nav-btn {
  background: #f8fafc; color: #374151; border: 1px solid #e5e7eb;
  padding: 8px 16px; border-radius: 999px; cursor: pointer; font-size: 13px;
}
.nav-btn:hover { border-color: #a5b4fc; color: #4f46e5; }
#player { width: 100%; max-height: 70vh; border-radius: 12px; margin: 16px 0; background: #000; }
.desc { color: #6b7280; font-size: 14px; margin-bottom: 14px; }
.steps { list-style: none; counter-reset: s; }
.steps li {
  counter-increment: s; position: relative; padding: 10px 12px 10px 46px;
  background: #f8fafc; border-radius: 10px; margin-bottom: 8px; font-size: 14px; line-height: 1.6; color: #374151;
}
.steps li::before {
  content: counter(s); position: absolute; left: 12px; top: 50%; transform: translateY(-50%);
  width: 24px; height: 24px; border-radius: 50%;
  background: linear-gradient(135deg, #6366f1, #8b5cf6); color: #fff; font-size: 12px; font-weight: 700;
  display: flex; align-items: center; justify-content: center;
}
.faq { margin-top: 26px; background: #f8fafc; border-radius: 14px; padding: 20px; border: 1px solid #f1f3f7; }
.faq h2 { color: #111827; margin-bottom: 10px; }
.faq li { margin: 6px 0 6px 18px; color: #4b5563; font-size: 14px; }
footer { text-align: center; color: #9ca3af; padding: 24px 0 8px; font-size: 13px; }

@media (max-width: 860px) {
  body { flex-direction: column; }
  .sidebar { width: 100%; height: auto; position: static; border-right: none; border-bottom: 1px solid #eef0f4; }
  .main { padding: 0 16px 32px; }
}