:root {
  --bg: #f6f7f9;
  --text: #1f2933;
  --muted: #637083;
  --line: #dde3ea;
  --brand: #0f766e;
  --brand-dark: #0b5f59;
  --surface: #ffffff;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  color: var(--text);
  background: var(--bg);
  font-family: Arial, "Microsoft YaHei", sans-serif;
  line-height: 1.7;
}

a {
  color: inherit;
  text-decoration: none;
}

img {
  display: block;
  max-width: 100%;
  height: auto;
}

.container {
  width: min(1180px, calc(100% - 32px));
  margin: 0 auto;
}

.site-header {
  background: var(--surface);
  border-bottom: 1px solid var(--line);
  position: sticky;
  top: 0;
  z-index: 10;
}

.header-inner {
  min-height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

.logo {
  font-size: 22px;
  font-weight: 700;
  color: var(--brand);
  white-space: nowrap;
}

.site-nav {
  display: flex;
  gap: 20px;
  flex-wrap: wrap;
  color: var(--muted);
}

.site-nav a:hover,
.site-nav [aria-current="page"] {
  color: var(--brand);
}

.hero {
  background: var(--surface);
  border-bottom: 1px solid var(--line);
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.1fr 0.9fr;
  gap: 40px;
  align-items: center;
  padding: 48px 0;
}

.eyebrow {
  color: var(--brand);
  font-weight: 700;
}

h1,
h2,
h3,
p {
  margin-top: 0;
}

h1 {
  font-size: 36px;
  line-height: 1.25;
  margin-bottom: 16px;
}

h2 {
  font-size: 24px;
  line-height: 1.35;
}

h3 {
  font-size: 17px;
  line-height: 1.45;
}

.hero-copy p {
  color: var(--muted);
  font-size: 17px;
}

.search-box {
  display: flex;
  margin-top: 24px;
  max-width: 520px;
}

.search-box input {
  flex: 1;
  min-width: 0;
  border: 1px solid var(--line);
  border-right: 0;
  padding: 13px 14px;
  font-size: 16px;
  border-radius: 6px 0 0 6px;
}

.search-box button {
  border: 0;
  background: var(--brand);
  color: #fff;
  padding: 0 22px;
  font-size: 16px;
  border-radius: 0 6px 6px 0;
  cursor: pointer;
}

.search-box button:hover {
  background: var(--brand-dark);
}

.featured-video {
  position: relative;
  display: block;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 8px;
  overflow: hidden;
}

.featured-video img {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
  background: #d8dee6;
}

.featured-video strong {
  display: block;
  padding: 16px;
  font-size: 18px;
}

.badge {
  position: absolute;
  top: 12px;
  left: 12px;
  background: var(--brand);
  color: #fff;
  padding: 4px 10px;
  border-radius: 4px;
  font-size: 13px;
}

.section {
  padding: 40px 0;
}

.muted {
  background: #eef3f2;
}

.section-title {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 20px;
}

.section-title a {
  color: var(--brand);
}

.video-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 18px;
}

.video-card {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 8px;
  overflow: hidden;
}

.video-card img {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
  background: #d8dee6;
}

.video-card h3,
.video-card p {
  padding: 0 14px;
}

.video-card h3 {
  margin: 14px 0 8px;
}

.video-card p {
  color: var(--muted);
  font-size: 14px;
  margin-bottom: 14px;
}

.two-column,
.content-layout {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 320px;
  gap: 28px;
}

.topic-list {
  padding-left: 20px;
}

.topic-list li {
  margin-bottom: 10px;
}

.notice,
.sidebar {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 20px;
}

.page {
  padding: 28px 0 44px;
}

.breadcrumb {
  display: flex;
  gap: 8px;
  color: var(--muted);
  font-size: 14px;
  margin-bottom: 16px;
}

.page-intro,
.meta {
  color: var(--muted);
}

.list {
  display: grid;
  gap: 18px;
}

.list-item {
  display: grid;
  grid-template-columns: 220px minmax(0, 1fr);
  gap: 18px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 14px;
}

.list-item img {
  width: 100%;
  aspect-ratio: 16 / 9;
  object-fit: cover;
  background: #d8dee6;
}

.list-item p,
.list-item time {
  color: var(--muted);
}

.sidebar {
  align-self: start;
  display: grid;
  gap: 10px;
}

.sidebar a {
  color: var(--brand);
}

.detail {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 24px;
}

.player {
  margin: 22px 0;
  background: #111827;
  border-radius: 8px;
  overflow: hidden;
}

.player video {
  display: block;
  width: 100%;
  aspect-ratio: 16 / 9;
}

.article-body {
  max-width: 820px;
}

.related {
  padding-bottom: 0;
}

.site-footer {
  background: #18212f;
  color: #d6dde8;
  padding: 24px 0;
}

.footer-inner {
  display: flex;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@media (max-width: 860px) {
  .header-inner,
  .footer-inner {
    align-items: flex-start;
    flex-direction: column;
  }

  .hero-grid,
  .two-column,
  .content-layout {
    grid-template-columns: 1fr;
  }

  .video-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  h1 {
    font-size: 28px;
  }
}

@media (max-width: 560px) {
  .video-grid,
  .list-item {
    grid-template-columns: 1fr;
  }

  .search-box {
    flex-direction: column;
  }

  .search-box input,
  .search-box button {
    width: 100%;
    border-radius: 6px;
    border: 1px solid var(--line);
  }

  .search-box button {
    margin-top: 10px;
    padding: 12px;
  }
}