:root {
  color-scheme: light;
  --bg: #fafafa;
  --text: #222;
  --primary: #1a1a1a;
  --accent: #002244;
  --accent-deep: #001728;
  --gold: #b8860b;
  --card: #fff;
  --border: #ccc;
  --shadow: 0 3px 12px rgba(0, 0, 0, 0.05);
  --shadow-strong: 0 6px 20px rgba(0, 0, 0, 0.2);
  --radius: 6px;
  --transition: 0.3s ease;
  --font-serif: "Source Han Serif SC", "Noto Serif SC", "Songti SC", "STSong", "SimSun", Georgia, serif;
  --font-sans: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans SC", Arial, sans-serif;
}

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

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
  color-scheme: light;
}

body {
  min-height: 100vh;
  font-family: var(--font-serif);
  background: var(--bg);
  color: var(--text);
  line-height: 1.68;
  padding-bottom: max(2rem, env(safe-area-inset-bottom));
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  -webkit-tap-highlight-color: rgba(0, 34, 68, 0.08);
}

body.overlay-open {
  overflow: hidden;
}

a,
button,
input,
textarea,
select {
  font: inherit;
  color: inherit;
}

button {
  background: none;
  border: 0;
  cursor: pointer;
}

img,
svg,
video {
  display: block;
  max-width: 100%;
}

[hidden] {
  display: none !important;
}

.skip-link {
  position: absolute;
  left: 1rem;
  top: -3rem;
  z-index: 1200;
  padding: 0.6rem 1rem;
  background: var(--accent);
  color: #fff;
  border-radius: 4px;
  text-decoration: none;
  transition: top var(--transition);
}

.skip-link:focus {
  top: max(0.75rem, env(safe-area-inset-top));
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: linear-gradient(135deg, var(--accent), var(--primary));
  color: #fff;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.08);
}

.site-header__inner {
  position: relative;
  max-width: 920px;
  margin: 0 auto;
  padding:
    max(1.2rem, calc(1rem + env(safe-area-inset-top)))
    max(1rem, env(safe-area-inset-right))
    1.2rem
    max(1rem, env(safe-area-inset-left));
  text-align: center;
}

.site-header h1 {
  font-size: clamp(1.45rem, 4vw, 1.9rem);
  font-weight: 700;
  line-height: 1.3;
}

.modal {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.6);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 1000;
  padding:
    max(1rem, env(safe-area-inset-top))
    max(1rem, env(safe-area-inset-right))
    max(1rem, env(safe-area-inset-bottom))
    max(1rem, env(safe-area-inset-left));
}

.modal.show {
  display: flex;
}

.modal-content {
  width: min(600px, 100%);
  max-height: min(80vh, 760px);
  overflow-y: auto;
  -webkit-overflow-scrolling: touch;
  background: var(--card);
  padding: 1.5rem;
  border-radius: var(--radius);
  box-shadow: var(--shadow-strong);
}

.modal-content h2 {
  color: var(--accent);
  margin-bottom: 0.8rem;
}

.modal-content h3 {
  color: var(--gold);
  margin: 0.8rem 0 0.4rem;
}

.modal-content p,
.modal-content li {
  line-height: 1.72;
}

.modal-content ol,
.modal-content ul {
  margin-left: 1rem;
  margin-bottom: 0.8rem;
}

.modal-close {
  margin-top: 1rem;
  min-height: 44px;
  padding: 0.45rem 1rem;
  background: var(--accent);
  color: #fff;
  border-radius: 4px;
}

.modal-close:hover,
.modal-close:focus-visible {
  background: var(--accent-deep);
}

#toc {
  position: fixed;
  top: max(20%, calc(4rem + env(safe-area-inset-top)));
  right: 1rem;
  width: 220px;
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0.8rem;
  box-shadow: 0 3px 10px rgba(0, 0, 0, 0.1);
  font-size: 0.9rem;
  z-index: 50;
}

#toc h4 {
  color: var(--accent);
  margin-bottom: 0.5rem;
}

#toc ul {
  list-style: none;
  padding: 0;
}

#toc li + li {
  margin-top: 0.4rem;
}

#toc a {
  display: block;
  padding: 0.2rem 0.4rem;
  color: var(--text);
  text-decoration: none;
  border-radius: 4px;
  transition: background var(--transition), color var(--transition);
}

#toc a:hover,
#toc a:focus-visible,
#toc a.is-active {
  background: var(--accent);
  color: #fff;
}

main {
  max-width: 920px;
  margin: 1.5rem auto;
  padding: 0 max(1rem, env(safe-area-inset-right)) 0 max(1rem, env(safe-area-inset-left));
}

.announcement {
  background: #fffaf0;
  border-left: 4px solid var(--gold);
  padding: 0.8rem;
  margin-bottom: 1.5rem;
  border-radius: 4px;
  display: none;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.03);
}

.announcement.is-visible {
  display: block;
}

.announcement h3 {
  color: var(--accent);
  margin-bottom: 0.4rem;
}

.announcement p {
  margin: 0;
}

.announcement[role="button"] {
  cursor: pointer;
}

section {
  background: var(--card);
  border-left: 4px solid var(--accent);
  margin-bottom: 1.5rem;
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  transition: border-left-color var(--transition), box-shadow var(--transition);
}

section:hover {
  border-left-color: var(--gold);
}

.section-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 0.8rem;
  padding: 0.8rem 1rem;
  background: #f7f7f7;
  cursor: pointer;
}

.section-header h2 {
  font-size: 1.18rem;
  color: var(--primary);
  margin: 0;
  line-height: 1.35;
}

.toggle-btn {
  min-width: 44px;
  min-height: 44px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 1.08rem;
  transition: transform var(--transition);
}

.toggle-btn[aria-expanded="true"] {
  transform: rotate(180deg);
}

.section-content {
  height: 0;
  padding: 0 1rem;
  overflow: hidden;
  border-top: 1px solid transparent;
  transition: height var(--transition), padding var(--transition), border-color var(--transition);
}

.section-content.open {
  padding: 0.8rem 1rem;
  border-top-color: var(--border);
}

.section-content h3 {
  color: var(--gold);
  margin-top: 0.8rem;
}

.section-content p,
.section-content li {
  margin-bottom: 0.8rem;
}

.section-content ol,
.section-content ul {
  margin-left: 1rem;
}

blockquote {
  margin: 0.8rem 0;
  padding-left: 0.8rem;
  border-left: 4px solid var(--gold);
  background: #fff8f0;
  font-style: italic;
  color: #555;
}

.video-item {
  margin: 0.9rem 0;
}

.video-banner {
  display: block;
  width: 100%;
  min-height: 48px;
  padding: 0.8rem 1rem 0.8rem 1.15rem;
  border: 1px solid rgba(0, 23, 40, 0.16);
  border-left: 3px solid rgba(184, 134, 11, 0.88);
  border-radius: 6px;
  background: linear-gradient(180deg, rgba(0, 34, 68, 0.96), rgba(0, 28, 56, 0.98));
  color: #fff;
  font-weight: 700;
  line-height: 1.65;
  text-align: left;
  white-space: normal;
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.08);
  transition:
    background var(--transition),
    border-color var(--transition),
    box-shadow var(--transition),
    opacity var(--transition);
}

.video-banner:hover,
.video-banner:focus-visible {
  background: linear-gradient(180deg, rgba(0, 28, 56, 0.98), rgba(0, 20, 39, 1));
  border-color: rgba(0, 23, 40, 0.24);
  box-shadow: 0 6px 18px rgba(0, 0, 0, 0.12);
}

.video-banner[aria-disabled="true"] {
  cursor: default;
  opacity: 0.96;
}

.video-banner[aria-disabled="true"]:hover,
.video-banner[aria-disabled="true"]:focus-visible {
  background: linear-gradient(180deg, rgba(0, 34, 68, 0.96), rgba(0, 28, 56, 0.98));
  border-color: rgba(0, 23, 40, 0.16);
  box-shadow: 0 4px 14px rgba(0, 0, 0, 0.08);
}

.video-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.75);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 1001;
  padding:
    max(1rem, env(safe-area-inset-top))
    max(1rem, env(safe-area-inset-right))
    max(1rem, env(safe-area-inset-bottom))
    max(1rem, env(safe-area-inset-left));
}

.video-overlay.active {
  display: flex;
}

.video-container {
  position: relative;
  width: min(80vw, 960px);
  max-height: 80vh;
  background: #000;
  border: 3px solid #fff;
  border-radius: 6px;
  box-shadow: 0 0 20px rgba(0, 0, 0, 0.5);
  overflow: hidden;
}

.video-container video {
  width: 100%;
  height: auto;
  max-height: 80vh;
  display: block;
}

.video-close {
  position: absolute;
  top: 0.5rem;
  right: 0.5rem;
  z-index: 1003;
  width: 40px;
  height: 40px;
  border-radius: 999px;
  background: rgba(0, 0, 0, 0.45);
  color: #fff;
  font-size: 1.45rem;
  line-height: 1;
}

.spinner {
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  width: 40px;
  height: 40px;
  border: 4px solid rgba(255, 255, 255, 0.3);
  border-top-color: #fff;
  border-radius: 50%;
  animation: spin 1s linear infinite;
  display: none;
  z-index: 1002;
}

@keyframes spin {
  to {
    transform: translate(-50%, -50%) rotate(360deg);
  }
}

#backToTop {
  position: fixed;
  right: max(1rem, env(safe-area-inset-right));
  bottom: max(1rem, env(safe-area-inset-bottom));
  min-width: 44px;
  min-height: 44px;
  padding: 0.5rem 0.75rem;
  border-radius: 4px;
  background: var(--accent);
  color: #fff;
  box-shadow: 0 3px 10px rgba(0, 0, 0, 0.2);
  display: none;
  z-index: 60;
}

#backToTop:hover,
#backToTop:focus-visible {
  background: var(--gold);
}

footer {
  text-align: center;
  padding: 1.5rem max(0.5rem, env(safe-area-inset-right)) max(1.5rem, env(safe-area-inset-bottom)) max(0.5rem, env(safe-area-inset-left));
  color: #777;
  font-size: 0.82rem;
}

@media (max-width: 768px) {
  #toc {
    display: none;
  }

  .section-header h2 {
    font-size: 1rem;
  }

  .modal-content {
    padding: 1.2rem;
  }

  .video-container {
    width: 100%;
  }
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }

  *,
  *::before,
  *::after {
    animation: none !important;
    transition: none !important;
  }
}