:root {
    --blue-900: #0b2a4a;
    --blue-700: #0e3f6e;
    --blue-600: #1268b3;
    --blue-500: #1f7fd4;
    --cyan-500: #00b8d9;
    --cyan-400: #22d3ee;
    --cyan-300: #67e8f9;
    --ink: #13293d;
    --muted: #5b7186;
    --bg: #f5f9fc;
    --card: #ffffff;
    --border: #e2ecf3;
    --radius: 16px;
    --shadow: 0 10px 30px rgba(14, 63, 110, .08);
    --grad: linear-gradient(135deg, #0e3f6e 0%, #1268b3 45%, #00b8d9 100%);
  }
  * { margin: 0; padding: 0; box-sizing: border-box; }
  html { scroll-behavior: smooth; }
  body {
    font-family: "PingFang SC", "Microsoft YaHei", "Segoe UI", system-ui, -apple-system, sans-serif;
    color: var(--ink);
    background: var(--bg);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
  }
  .container { max-width: 1120px; margin: 0 auto; padding: 0 24px; }

  /* ===== 顶部导航 ===== */
  header.site-header {
    position: sticky; top: 0; z-index: 50;
    background: rgba(255, 255, 255, .92);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border);
  }
  .nav { display: flex; align-items: center; justify-content: space-between; height: 64px; gap: 16px; }
  .brand { display: flex; align-items: center; gap: 10px; text-decoration: none; color: var(--blue-900); font-weight: 700; }
  .brand img { width: 34px; height: 34px; border-radius: 8px; object-fit: cover; }
  .brand .brand-name { font-size: 17px; letter-spacing: .5px; white-space: nowrap; }
  .nav-links { display: flex; align-items: center; gap: 6px; list-style: none; }
  .nav-links a { display: block; padding: 8px 14px; border-radius: 10px; color: var(--ink); text-decoration: none; font-size: 14px; font-weight: 500; transition: background .2s, color .2s; }
  .nav-links a:hover { background: #e8f4fc; color: var(--blue-600); }
  .nav-download { background: var(--grad); color: #fff !important; }
  .nav-download:hover { opacity: .92; background: var(--grad); }
  .nav-toggle {
    display: none; border: none; background: none; cursor: pointer;
    width: 40px; height: 40px; border-radius: 10px; color: var(--blue-900);
  }
  .nav-toggle svg { width: 24px; height: 24px; }

  /* ===== Hero ===== */
  .hero {
    position: relative; overflow: hidden;
    background: var(--grad);
    color: #fff;
    padding: 84px 0 72px;
    text-align: center;
  }
  .hero::before, .hero::after {
    content: ""; position: absolute; border-radius: 50%; filter: blur(60px); opacity: .35;
  }
  .hero::before { width: 380px; height: 380px; background: var(--cyan-400); top: -120px; right: -80px; }
  .hero::after { width: 300px; height: 300px; background: #7cc7ff; bottom: -120px; left: -60px; }
  .hero .container { position: relative; z-index: 1; }
  .hero-badge {
    display: inline-flex; align-items: center; gap: 8px;
    background: rgba(255, 255, 255, .14); border: 1px solid rgba(255, 255, 255, .28);
    padding: 6px 16px; border-radius: 999px; font-size: 13px; letter-spacing: 1px;
    margin-bottom: 22px; backdrop-filter: blur(6px);
  }
  .hero h1 { font-size: clamp(30px, 5vw, 48px); font-weight: 800; line-height: 1.25; margin-bottom: 18px; }
  .hero h1 .hl { background: linear-gradient(90deg, #67e8f9, #ffffff); -webkit-background-clip: text; background-clip: text; -webkit-text-fill-color: transparent; }
  .hero p.lead { max-width: 640px; margin: 0 auto 34px; font-size: clamp(15px, 2.2vw, 18px); color: rgba(255, 255, 255, .9); }
  .hero-actions { display: flex; flex-wrap: wrap; justify-content: center; gap: 14px; align-items: center; }
  .btn {
    display: inline-flex; align-items: center; gap: 8px;
    padding: 14px 30px; border-radius: 999px; font-size: 16px; font-weight: 700;
    text-decoration: none; transition: transform .2s, box-shadow .2s, background .2s;
    border: none; cursor: pointer;
  }
  .btn-primary { background: #fff; color: var(--blue-700); box-shadow: 0 8px 20px rgba(11, 42, 74, .25); }
  .btn-primary:hover { transform: translateY(-2px); box-shadow: 0 12px 26px rgba(11, 42, 74, .32); }
  .btn-primary svg { width: 20px; height: 20px; }
  .btn-ghost { background: transparent; color: #fff; border: 1.5px solid rgba(255,255,255,.55); }
  .btn-ghost:hover { background: rgba(255,255,255,.12); transform: translateY(-2px); }
  .hero-meta { margin-top: 22px; font-size: 13px; color: rgba(255,255,255,.75); }
  .hero-meta span { margin: 0 10px; opacity: .6; }

  /* ===== 杀软误报提示 ===== */
  .av-notice {
    max-width: 640px; margin: 26px auto 0; text-align: left;
    background: rgba(255, 255, 255, .12); border: 1px solid rgba(255, 255, 255, .3);
    border-radius: 14px; padding: 14px 18px;
    font-size: 13px; color: rgba(255, 255, 255, .92); backdrop-filter: blur(6px);
  }
  .av-notice strong { color: #fff; }
  .av-notice code {
    background: rgba(255,255,255,.2); padding: 1px 7px; border-radius: 6px;
    font-size: 12px; word-break: break-all;
  }

  /* ===== 区块通用 ===== */
  section { padding: 72px 0; }
  .section-head { text-align: center; max-width: 640px; margin: 0 auto 44px; }
  .section-head .tag {
    display: inline-block; color: var(--blue-600); font-size: 13px; font-weight: 700;
    letter-spacing: 2px; text-transform: uppercase; margin-bottom: 10px;
  }
  .section-head h2 { font-size: clamp(24px, 3.6vw, 34px); font-weight: 800; color: var(--blue-900); }
  .section-head p { margin-top: 12px; color: var(--muted); font-size: 15px; }

  /* ===== 功能卡片 ===== */
  .features { background: #fff; }
  .cards {
    display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px;
  }
  .card {
    background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
    padding: 26px; box-shadow: var(--shadow);
    transition: transform .25s, box-shadow .25s, border-color .25s;
  }
  .card:hover { transform: translateY(-6px); box-shadow: 0 18px 40px rgba(14, 63, 110, .14); border-color: var(--cyan-400); }
  .card .icon {
    width: 52px; height: 52px; border-radius: 14px;
    display: flex; align-items: center; justify-content: center;
    background: linear-gradient(135deg, #e3f4ff, #d9f7fb); color: var(--blue-600);
    margin-bottom: 16px;
  }
  .card .icon svg { width: 26px; height: 26px; }
  .card h3 { font-size: 17px; font-weight: 700; color: var(--blue-900); margin-bottom: 8px; }
  .card p { font-size: 14px; color: var(--muted); }

  /* ===== 格式列表 ===== */
  .formats { background: var(--bg); }
  .format-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 22px; }
  .format-box {
    background: #fff; border: 1px solid var(--border); border-radius: var(--radius);
    padding: 26px 30px; box-shadow: var(--shadow);
  }
  .format-box h3 { display: flex; align-items: center; gap: 10px; font-size: 17px; color: var(--blue-900); margin-bottom: 16px; }
  .format-box h3 svg { width: 22px; height: 22px; color: var(--cyan-500); }
  .tags { display: flex; flex-wrap: wrap; gap: 10px; }
  .tag-item {
    display: inline-flex; align-items: center; gap: 6px;
    background: #eef7fd; color: var(--blue-700); border: 1px solid #d8eaf6;
    padding: 5px 13px; border-radius: 999px; font-size: 13px; font-weight: 600;
  }
  .tag-item small { color: var(--muted); font-weight: 400; }
  .format-note { margin-top: 18px; font-size: 13px; color: var(--muted); }

  /* ===== FFmpeg 说明 ===== */
  .ffmpeg { background: #fff; }
  .ffmpeg-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 22px; }
  .step-card {
    border: 1px solid var(--border); border-radius: var(--radius); padding: 24px 26px;
    background: var(--card);
  }
  .step-card .step-no {
    width: 34px; height: 34px; border-radius: 50%;
    background: var(--grad); color: #fff; font-weight: 800; font-size: 15px;
    display: flex; align-items: center; justify-content: center; margin-bottom: 14px;
  }
  .step-card h3 { font-size: 16px; color: var(--blue-900); margin-bottom: 8px; }
  .step-card p, .step-card li { font-size: 14px; color: var(--muted); }
  .step-card ol, .step-card ul { margin: 8px 0 0 20px; }
  .step-card li { margin: 5px 0; }
  .step-card code {
    background: #eef7fd; color: var(--blue-700); border: 1px solid #d8eaf6;
    padding: 1px 8px; border-radius: 7px; font-size: 13px; font-family: Consolas, "Courier New", monospace;
    word-break: break-all;
  }
  .ffmpeg-tip {
    grid-column: 1 / -1;
    background: linear-gradient(135deg, #e8f7fb, #eef2fd);
    border: 1px solid #cfeaf4; border-radius: var(--radius);
    padding: 18px 24px; font-size: 14px; color: var(--blue-900);
    display: flex; gap: 12px; align-items: flex-start;
  }
  .ffmpeg-tip svg { width: 22px; height: 22px; flex-shrink: 0; color: var(--blue-600); margin-top: 2px; }

  /* ===== 下载 CTA ===== */
  .cta { background: var(--grad); color: #fff; text-align: center; }
  .cta h2 { font-size: clamp(24px, 3.6vw, 34px); font-weight: 800; margin-bottom: 12px; }
  .cta p { color: rgba(255,255,255,.9); margin-bottom: 30px; }
  .cta .btn-primary { font-size: 18px; padding: 16px 38px; }
  .cta-av {
    max-width: 640px; margin: 24px auto 0; text-align: left;
    background: rgba(255,255,255,.14); border: 1px solid rgba(255,255,255,.3);
    border-radius: 14px; padding: 14px 18px; font-size: 13px; color: rgba(255,255,255,.92);
  }
  .cta-av strong { color: #fff; }
  .cta-av code { background: rgba(255,255,255,.2); padding: 1px 7px; border-radius: 6px; font-size: 12px; }

  /* ===== 页脚 ===== */
  footer.site-footer { background: var(--blue-900); color: rgba(255,255,255,.8); padding: 40px 0 32px; }
  .footer-inner { display: flex; flex-wrap: wrap; gap: 20px; align-items: center; justify-content: space-between; }
  .footer-brand { display: flex; align-items: center; gap: 10px; font-weight: 700; color: #fff; }
  .footer-brand img { width: 30px; height: 30px; border-radius: 8px; }
  .footer-copy { font-size: 13px; text-align: right; }
  .footer-copy span { display: block; }

  /* ===== 响应式 ===== */
  @media (max-width: 900px) {
    .cards { grid-template-columns: repeat(2, 1fr); }
  }
  @media (max-width: 720px) {
    .nav-toggle { display: inline-flex; align-items: center; justify-content: center; }
    .nav-links {
      display: none; position: absolute; top: 64px; left: 0; right: 0;
      flex-direction: column; align-items: stretch; gap: 4px;
      background: #fff; border-bottom: 1px solid var(--border);
      padding: 12px 16px 18px; box-shadow: 0 20px 30px rgba(11,42,74,.08);
    }
    .nav-links.open { display: flex; }
    .nav-links a { padding: 12px 16px; }
    .format-grid, .ffmpeg-grid { grid-template-columns: 1fr; }
    .hero { padding: 64px 0 56px; }
    section { padding: 56px 0; }
  }
  @media (max-width: 560px) {
    .cards { grid-template-columns: 1fr; }
    .hero-actions .btn { width: 100%; justify-content: center; }
    .footer-inner { flex-direction: column; text-align: center; }
    .footer-copy { text-align: center; }
  }
  /* ===== 背景音乐与歌词展示 ===== */
  .music { background: #fff; }
  .music-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 22px; align-items: start; }
  .music-card {
    background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
    padding: 26px 30px; box-shadow: var(--shadow);
  }
  .music-card .icon {
    width: 52px; height: 52px; border-radius: 14px;
    display: flex; align-items: center; justify-content: center;
    background: linear-gradient(135deg, #e3f4ff, #d9f7fb); color: var(--blue-600);
    margin-bottom: 16px;
  }
  .music-card .icon svg { width: 26px; height: 26px; }
  .music-card h3 { font-size: 17px; font-weight: 700; color: var(--blue-900); margin-bottom: 10px; }
  .music-card p { font-size: 14px; color: var(--muted); }
  .music-card ul { margin: 4px 0 14px 20px; }
  .music-card li { font-size: 14px; color: var(--muted); margin: 5px 0; }
  .music-card strong { color: var(--blue-700); }
  .music-card code {
    background: #eef7fd; color: var(--blue-700); border: 1px solid #d8eaf6;
    padding: 1px 8px; border-radius: 7px; font-size: 12.5px;
    font-family: Consolas, "Courier New", monospace; word-break: break-all;
  }
  .player { width: 100%; margin: 6px 0 14px; }
  .sample-note { font-size: 13px; color: var(--muted); margin-bottom: 12px; }
  .lyric-box {
    background: #f8fcff; border: 1px solid #d8eaf6; border-radius: 12px;
    padding: 14px 18px; max-height: 340px; overflow-y: auto;
    font-size: 14px; line-height: 1.9; color: var(--ink);
  }
  .lyric-box .lyric-title { font-weight: 800; color: var(--blue-900); }
  .lyric-box .lyric-section { color: var(--blue-600); font-weight: 700; margin-top: 4px; }
  .lyric-box .lyric-time {
    color: var(--cyan-500); font-family: Consolas, "Courier New", monospace;
    font-size: 12px; margin-right: 2px;
  }
  .lyric-box .lyric-ellipsis { color: var(--muted); font-size: 13px; }

  /* 试听区歌词当前句高亮：蓝色加粗 + 淡蓝渐变底（配合 1.mp3 播放同步） */
  .lyric-box p.lyric-current {
    color: var(--blue-600);
    font-weight: 700;
    background: linear-gradient(90deg, #e3f4ff, #d9f7fb);
    border-radius: 6px;
    padding: 0 6px;
    transition: background .2s ease, color .2s ease;
  }
  .music-sample { grid-column: 1 / -1; }
  .music-sample .sample-note.autoplay-tip { margin-top: 6px; color: var(--muted); font-size: 13px; }
  .music-sample .autoplay-tip.autoplay-warn { color: var(--blue-600); font-weight: 600; }

  @media (max-width: 720px) {
    .music-grid { grid-template-columns: 1fr; }
  }

  /* ===== 下载菜单（md 驱动）===== */
  .dl-menu {
    display: none;
    position: absolute;
    z-index: 120;
    min-width: 250px;
    max-width: 320px;
    background: #fff;
    border: 1px solid var(--border);
    border-radius: 14px;
    box-shadow: 0 18px 44px rgba(11, 42, 74, .16);
    padding: 16px 20px;
    font-size: 14px;
    color: var(--ink);
  }
  .dl-menu.open { display: block; }
  .dl-menu h2, .dl-menu h3 {
    font-size: 14px; font-weight: 800; color: var(--blue-900);
    margin-bottom: 10px; padding-bottom: 8px; border-bottom: 1px solid var(--border);
  }
  .dl-menu ul { list-style: none; margin: 0; }
  .dl-menu li { margin: 8px 0; }
  .dl-menu li a {
    display: block; text-decoration: none; color: var(--blue-600); font-weight: 700;
    padding: 8px 12px; border-radius: 10px; background: #eef7fd;
    transition: background .2s, color .2s;
  }
  .dl-menu li a:hover { background: #d9f7fb; color: var(--blue-900); }
  .dl-menu p { font-size: 12.5px; color: var(--muted); margin-top: 8px; }
  .dl-menu .md-quote {
    margin-top: 10px; padding: 9px 12px; background: #f8fcff;
    border-left: 3px solid var(--cyan-500); border-radius: 6px;
    font-size: 12.5px; color: var(--muted); line-height: 1.7;
  }
  .dl-menu code {
    background: #eef7fd; color: var(--blue-700);
    padding: 1px 6px; border-radius: 6px; font-size: 12px;
  }

  /* ===== 介绍使用说明 ===== */
  .guide { background: var(--bg); }
  .guide-card {
    max-width: 860px; margin: 0 auto;
    background: #fff; border: 1px solid var(--border); border-radius: var(--radius);
    box-shadow: var(--shadow); padding: 34px 40px;
    line-height: 1.85; font-size: 14.5px; color: var(--ink);
  }
  .guide-card h2 {
    font-size: 19px; font-weight: 800; color: var(--blue-900);
    margin: 30px 0 12px; padding-bottom: 8px; border-bottom: 1px solid var(--border);
  }
  .guide-card h2:first-child { margin-top: 0; }
  .guide-card h3 { font-size: 16px; color: var(--blue-700); margin: 18px 0 8px; }
  .guide-card h4 { font-size: 15px; color: var(--blue-700); margin: 14px 0 6px; }
  .guide-card p { margin: 8px 0; }
  .guide-card ul, .guide-card ol { margin: 8px 0 8px 22px; }
  .guide-card li { margin: 6px 0; }
  .guide-card code {
    background: #eef7fd; color: var(--blue-700); border: 1px solid #d8eaf6;
    padding: 1px 8px; border-radius: 7px; font-size: 13px;
    font-family: Consolas, "Courier New", monospace; word-break: break-all;
  }
  .guide-card a { color: var(--blue-600); text-decoration: none; }
  .guide-card a:hover { text-decoration: underline; }
  .guide-card .md-quote {
    background: #f8fcff; border-left: 3px solid var(--cyan-500);
    padding: 10px 14px; border-radius: 8px; color: var(--muted); font-size: 13.5px;
  }
  .guide-loading { color: var(--muted); text-align: center; padding: 24px 0; }
  .guide-error { color: #c0392b; text-align: center; padding: 24px 0; }

  @media (max-width: 720px) {
    .guide-card { padding: 24px 22px; }
  }

  /* ===== 赞助 ===== */
  .sponsor { background: var(--bg); }
  .sponsor-card {
    max-width: 720px; margin: 0 auto;
    background: var(--card); border: 1px solid var(--border); border-radius: var(--radius);
    padding: 26px 30px; box-shadow: var(--shadow);
  }
  .sponsor-card .info h3 { font-size: 18px; color: var(--blue-900); margin-bottom: 10px; }
  .sponsor-card .info p { font-size: 14px; color: var(--muted); line-height: 1.7; margin-bottom: 16px; }
  .sponsor-list { list-style: none; border-top: 1px solid var(--border); }
  .sponsor-list li {
    display: flex; align-items: center; gap: 12px;
    padding: 10px 4px; border-bottom: 1px solid var(--border);
    font-size: 14px; color: var(--ink);
  }
  .sponsor-list li.empty { justify-content: center; color: var(--muted); padding: 18px 4px; }
  .sponsor-list .rk {
    min-width: 24px; text-align: center; font-size: 13px; font-weight: 700;
    color: var(--blue-600); background: #eaf4fb; border-radius: 6px; padding: 2px 6px;
  }
  .sponsor-list .nm { flex: 1; min-width: 0; font-weight: 600; }
  .sponsor-list .amt { color: #b07c1f; font-weight: 700; }
  .sponsor-list .tm { color: var(--muted); font-size: 13px; white-space: nowrap; }

  @media (max-width: 560px) {
    .sponsor-card { padding: 20px 16px; }
    .sponsor-list li { flex-wrap: wrap; gap: 6px 10px; }
    .sponsor-list .tm { width: 100%; padding-left: 36px; }
  }

  /* ===== 在线视频（B 站播放器 iframe 挂载） ===== */
  .cta-video {
    margin: 14px 0 0;
    display: flex;
    flex-direction: column;
    gap: 14px;
    align-items: stretch;
  }
  .video-embed-frame {
    display: block;
    width: 100%;
    height: 320px;
    border: 0;
    border-radius: 12px;
    box-shadow: 0 2px 10px rgba(0, 161, 214, 0.25);
  }
  .video-click-play {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 10px;
    width: 100%;
    height: 320px;
    border-radius: 12px;
    background: linear-gradient(135deg, #16233a, #0b2a4a);
    color: #fff;
    cursor: pointer;
    text-align: center;
    padding: 20px;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.18);
    user-select: none;
    transition: background 0.2s ease, transform 0.2s ease, box-shadow 0.2s ease;
  }
  .video-click-play:hover {
    background: linear-gradient(135deg, #1d3350, #0e3f6e);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(0, 0, 0, 0.28);
  }
  .video-click-play .vcp-icon {
    width: 52px;
    height: 52px;
    padding: 12px;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.18);
    box-sizing: border-box;
  }
  .video-click-play .vcp-title {
    font-size: 15px;
    font-weight: 600;
    line-height: 1.5;
    max-width: 90%;
    word-break: break-word;
  }
  .video-click-play .vcp-hint {
    font-size: 13px;
    color: rgba(255, 255, 255, 0.75);
    letter-spacing: 1px;
  }

  @media (max-width: 560px) {
    .video-embed-frame { height: 220px; }
    .video-click-play { height: 220px; }
    .video-click-play .vcp-icon { width: 44px; height: 44px; padding: 10px; }
  }