:root {
  --primary: #0033ff;
  --primary-dark: #0029cc;
  --primary-soft: rgba(0, 51, 255, 0.12);
  --text: #1a1a2e;
  --muted: #5c6370;
  --border: #e8ecf4;
  --bg: #f4f6fb;
  --white: #fff;
  --radius: 10px;
  --shadow: 0 8px 28px rgba(0, 51, 255, 0.08);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  color: var(--text);
  background: var(--bg);
  line-height: 1.6;
}

a {
  color: var(--primary);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

.site-header {
  background: var(--primary);
  color: var(--white);
  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.12);
}

.header-inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 20px;
  display: flex;
  align-items: center;
  gap: 24px;
  min-height: 56px;
  flex-wrap: wrap;
}

.brand {
  font-weight: 600;
  font-size: 1.05rem;
  color: var(--white);
  white-space: nowrap;
}

.brand:hover {
  text-decoration: none;
  opacity: 0.95;
}

.top-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 4px 18px;
  align-items: center;
  flex: 1;
}

.top-nav a,
.nav-drop > summary {
  color: var(--white);
  font-size: 0.92rem;
  cursor: pointer;
  list-style: none;
}

.top-nav a:hover {
  text-decoration: underline;
}

.nav-drop {
  position: relative;
}

.nav-drop > summary::-webkit-details-marker {
  display: none;
}

.nav-drop[open] summary {
  opacity: 0.9;
}

.nav-drop menu {
  position: absolute;
  top: calc(100% + 8px);
  left: 0;
  margin: 0;
  padding: 8px 0;
  min-width: 180px;
  background: var(--white);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  border: 1px solid var(--border);
  z-index: 20;
}

.nav-drop menu a {
  display: block;
  padding: 8px 16px;
  color: var(--text);
}

.nav-drop menu a:hover {
  background: var(--primary-soft);
  text-decoration: none;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: 10px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 8px 16px;
  border-radius: 8px;
  font-size: 0.9rem;
  font-weight: 500;
  border: none;
  cursor: pointer;
}

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

.btn-primary:hover {
  background: #f0f4ff;
  text-decoration: none;
}

.btn-ghost {
  background: transparent;
  color: var(--white);
  border: 1px solid rgba(255, 255, 255, 0.55);
}

.btn-ghost:hover {
  background: rgba(255, 255, 255, 0.12);
  text-decoration: none;
}

.hero {
  background: linear-gradient(135deg, var(--primary) 0%, #335dff 55%, #5c7cff 100%);
  color: var(--white);
  padding: 48px 20px 56px;
}

.hero-inner {
  max-width: 720px;
  margin: 0 auto;
  text-align: center;
}

.hero h1 {
  margin: 0 0 12px;
  font-size: clamp(1.5rem, 4vw, 2rem);
  font-weight: 700;
}

.hero p {
  margin: 0 0 28px;
  opacity: 0.92;
  font-size: 1rem;
}

.search-form {
  display: flex;
  max-width: 560px;
  margin: 0 auto;
  background: var(--white);
  border-radius: 999px;
  overflow: hidden;
  box-shadow: 0 4px 20px rgba(0, 0, 0, 0.15);
}

.search-form input {
  flex: 1;
  border: none;
  padding: 14px 20px;
  font-size: 1rem;
  outline: none;
}

.search-form button {
  border: none;
  background: var(--primary);
  color: var(--white);
  padding: 0 24px;
  font-size: 0.95rem;
  cursor: pointer;
  font-weight: 500;
}

.search-form button:hover {
  background: var(--primary-dark);
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  justify-content: center;
  margin-top: 24px;
}

.btn-hero-primary {
  display: inline-flex;
  align-items: center;
  padding: 12px 28px;
  border-radius: 999px;
  background: var(--white);
  color: var(--primary);
  font-weight: 600;
  text-decoration: none;
  box-shadow: 0 4px 16px rgba(0, 0, 0, 0.12);
}

.btn-hero-primary:hover {
  text-decoration: none;
  background: #f0f4ff;
}

.btn-hero-outline {
  display: inline-flex;
  align-items: center;
  padding: 12px 28px;
  border-radius: 999px;
  border: 2px solid rgba(255, 255, 255, 0.85);
  color: var(--white);
  font-weight: 500;
  text-decoration: none;
}

.btn-hero-outline:hover {
  text-decoration: none;
  background: rgba(255, 255, 255, 0.12);
}

.header-actions .portal-register {
  border: 1px solid rgba(255, 255, 255, 0.45);
  margin-left: 4px;
}

.portal-user {
  color: var(--white);
  font-size: 0.9rem;
  margin-right: 8px;
  white-space: nowrap;
}

.main {
  max-width: 1200px;
  margin: 0 auto;
  padding: 32px 20px 48px;
}

.section-title {
  font-size: 1.25rem;
  margin: 0 0 20px;
  font-weight: 600;
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 20px;
}

.card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
  transition: box-shadow 0.2s, border-color 0.2s;
}

.card:hover {
  border-color: rgba(0, 51, 255, 0.35);
  box-shadow: var(--shadow);
}

.card h3 {
  margin: 0 0 8px;
  font-size: 1.05rem;
}

.card p {
  margin: 0 0 14px;
  color: var(--muted);
  font-size: 0.9rem;
}

.card .link {
  font-weight: 500;
  font-size: 0.9rem;
}

.two-col {
  display: grid;
  grid-template-columns: 1fr 320px;
  gap: 28px;
  margin-top: 40px;
}

@media (max-width: 900px) {
  .two-col {
    grid-template-columns: 1fr;
  }
}

.side-box {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
}

.side-box h3 {
  margin: 0 0 12px;
  font-size: 1rem;
}

.side-box ul {
  margin: 0;
  padding-left: 18px;
  color: var(--muted);
  font-size: 0.9rem;
}

.video-wrap {
  position: relative;
  padding-bottom: 56.25%;
  height: 0;
  overflow: hidden;
  border-radius: var(--radius);
  background: #000;
  margin-top: 12px;
}

.video-wrap iframe {
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  border: 0;
}

.video-placeholder {
  padding: 24px;
  text-align: center;
  color: var(--muted);
  font-size: 0.88rem;
  background: var(--bg);
  border-radius: var(--radius);
  border: 1px dashed var(--border);
}

.site-footer {
  text-align: center;
  padding: 24px 20px;
  color: var(--muted);
  font-size: 0.85rem;
  border-top: 1px solid var(--border);
  background: var(--white);
}

.intro-page .breadcrumb {
  font-size: 0.88rem;
  color: var(--muted);
  margin-bottom: 16px;
}

.intro-page h1 {
  margin: 0 0 8px;
}

.intro-page .lead {
  color: var(--muted);
  margin-bottom: 28px;
}

.topic-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.topic-list li {
  border-bottom: 1px solid var(--border);
  padding: 14px 0;
}

.topic-list li:last-child {
  border-bottom: none;
}

.topic-list a {
  font-weight: 500;
}

.topic-list span {
  display: block;
  color: var(--muted);
  font-size: 0.88rem;
  margin-top: 4px;
}