:root{
    --c-bg:#0b0b0d;
    --c-bg-soft:#151517;
    --c-card:#1a1a1d;
    --c-border:#2a2a30;
    --c-text:#f5f5f7;
    --c-text-dim:#a8a8b3;
    --c-text-mut:#6a6a76;
    --c-brand:#f5c518;
    --c-brand-2:#ffb327;
    --c-accent:#e8b923;
    --c-warn:#f0a838;
    --c-ok:#3dd97e;
    --radius:12px;
    --shadow:0 12px 32px rgba(0,0,0,.55),0 2px 8px rgba(0,0,0,.4);
  }
  *{box-sizing:border-box}
  html,body{margin:0;padding:0}
  body{
    background:radial-gradient(1100px 520px at 78% -8%, rgba(245,197,24,.07), transparent 58%),
               radial-gradient(820px 460px at -8% 12%, rgba(255,179,39,.05), transparent 58%),
               var(--c-bg);
    color:var(--c-text);
    font-family:"PingFang SC","Microsoft YaHei","Segoe UI",-apple-system,sans-serif;
    min-height:100vh;
    line-height:1.6;
  }
  .app{display:flex;flex-direction:column;height:100vh;width:100%;padding:0 28px 20px;box-sizing:border-box}

  /* ---------- Topbar ---------- */
  .topbar{
    display:flex;align-items:center;gap:16px;
    padding:14px 0 12px;border-bottom:none;
  }
  .topbar-left{display:flex;align-items:center;flex:0 0 auto}
  .topbar-left .logo{height:44px;width:auto;margin-right:16px;flex:0 0 auto;display:block}
  .topbar-right{display:flex;align-items:center;gap:10px;flex:0 0 auto}
  .topbar .search{width:480px}
  .topbar > .tabs{margin:0 auto}

  .tabs{display:inline-flex;background:var(--c-bg-soft);border:1px solid var(--c-border);border-radius:999px;padding:4px;gap:4px}
  .tabs button{
    border:0;background:transparent;color:var(--c-text-dim);
    padding:9px 20px;border-radius:999px;cursor:pointer;font-size:14px;font-weight:600;
    transition:all .2s;white-space:nowrap;
  }
  .tabs button:hover{color:var(--c-text)}
  .tabs button.active{
    background:rgba(245,197,24,.14);
    color:var(--c-brand);box-shadow:none;
  }

  /* ---------- Main grid ---------- */
  .main{
    display:grid;grid-template-columns:minmax(0,1fr) 480px;gap:24px;
    margin-top:12px;flex:1 1 auto;min-height:0;align-items:stretch;
  }
  .player-col{min-width:0;min-height:0;display:flex;flex-direction:column;overflow-y:auto;overscroll-behavior:contain}
  .right-col{min-height:0;display:flex;flex-direction:column;gap:14px}
  .panel{
    background:var(--c-card);border:1px solid var(--c-border);border-radius:var(--radius);
    box-shadow:var(--shadow);overflow:hidden;
  }
  .player-wrap{padding:18px;height:100%;display:flex;flex-direction:column}
  .player-title{flex:0 0 auto}
  .player-box{
    position:relative;width:100%;flex:1 1 auto;min-height:0;background:#000;border-radius:0;overflow:hidden;
    display:flex;align-items:center;justify-content:center;
  }
  .player-box video{width:100%;height:100%;border:0;display:block;object-fit:contain;background:#000}
  .player-box iframe{width:100%;height:100%;border:0;display:block}
  .player-meta{flex:0 0 auto}
  .player-box .placeholder{
    color:var(--c-text-dim);text-align:center;padding:24px;font-size:14px;
    display:flex;flex-direction:column;align-items:center;gap:10px;
  }
  .player-box .placeholder .big{font-size:40px;opacity:.6}
  .player-box .placeholder.coming{color:var(--c-warn)}
  .player-meta{padding:14px 4px 2px}
  .player-meta .code{font-size:12px;color:var(--c-brand);font-weight:700;letter-spacing:.5px}
  .player-meta h2{margin:8px 0 4px;font-size:17px;line-height:1.4}
  .nav-row{
    display:flex;align-items:center;gap:10px;margin-top:8px;
    padding-top:0;
    justify-content:space-between;
  }
  .nav-btn{
    display:inline-flex;align-items:center;gap:7px;
    background:var(--c-bg-soft);color:#fff;border:1px solid #4a4a55;
    padding:6px 14px;border-radius:8px;cursor:pointer;font-size:13px;font-weight:600;
    transition:all .15s;font-family:inherit;
  }
  .nav-btn:hover:not(:disabled){color:var(--c-text);border-color:var(--c-brand);background:rgba(245,197,24,.12)}
  .nav-btn:disabled{opacity:.35;cursor:not-allowed}
  .nav-btn.autonext:enabled{color:#fff}
  .nav-btn.copy-btn{
    border-radius:999px;
    border-color:#6a6a76;color:#f4f4f7;background:rgba(255,255,255,.06);
  }
  .nav-btn.copy-btn:hover{background:rgba(255,255,255,.13);border-color:#fff;color:#fff}
  #copyTip{
    position:fixed;left:50%;bottom:34px;transform:translate(-50%,10px);z-index:99999;
    background:#1c1c24;color:#fff;border:1px solid rgba(124,108,247,.5);
    padding:9px 16px;border-radius:8px;font-size:13px;box-shadow:0 8px 30px rgba(0,0,0,.5);
    opacity:0;pointer-events:none;transition:opacity .2s,transform .2s;white-space:nowrap;
  }
  #copyTip.show{opacity:1;transform:translate(-50%,0)}
  .nav-pos{font-size:12px;color:var(--c-text-mut);text-align:center;font-variant-numeric:tabular-nums;white-space:nowrap}
  .player-title{padding:0 4px 12px;display:flex;align-items:center;gap:8px;min-width:0}
  .player-title .nav-code{font-size:16px;color:#fff;font-weight:700;flex:0 0 auto}
  .player-title .nav-title{
    font-size:14px;color:var(--c-text);line-height:1.4;font-weight:600;
    white-space:nowrap;overflow:hidden;text-overflow:ellipsis;min-width:0;
  }
  .ext-btn-row{margin-top:8px}
  .ext-btn{
    display:inline-flex;align-items:center;gap:8px;background:linear-gradient(135deg,var(--c-brand),var(--c-brand-2));color:#1a1a1d;text-decoration:none;
    padding:11px 22px;border-radius:10px;font-weight:700;font-size:14px;
    box-shadow:0 6px 16px rgba(245,197,24,.4);transition:transform .15s;
  }
  .ext-btn:hover{transform:translateY(-1px)}

  /* ---------- Search box (topbar right) ---------- */
  .search{flex:1;min-width:0;position:relative;display:flex;align-items:center}
  .search > svg{position:absolute;left:12px;width:16px;height:16px;color:var(--c-text-mut);pointer-events:none}
  .search input{
    width:100%;padding:11px 40px 11px 40px;border-radius:999px;
    background:linear-gradient(180deg,rgba(255,255,255,.05),rgba(255,255,255,.02)),var(--c-bg-soft);
    border:1.5px solid rgba(255,255,255,.18);color:var(--c-text);
    font-size:14px;outline:none;
    box-shadow:inset 0 1px 0 rgba(255,255,255,.05);
    transition:border-color .2s,box-shadow .2s,background .2s,transform .15s;
  }
  .search input:hover{border-color:rgba(245,197,24,.75);box-shadow:0 2px 14px rgba(245,197,24,.28)}
  .search input:focus{border-color:var(--c-brand);background:linear-gradient(180deg,rgba(255,255,255,.07),rgba(255,255,255,.03)),var(--c-bg-soft);box-shadow:0 0 0 3px rgba(245,197,24,.22),0 4px 18px rgba(245,197,24,.30)}
  .search input::placeholder{color:rgba(255,255,255,.55)}
  /* 清除按钮 */
  .clear-btn{position:absolute;right:10px;top:50%;transform:translateY(-50%);width:20px;height:20px;display:none;align-items:center;justify-content:center;background:rgba(255,255,255,.12);border:none;border-radius:50%;color:rgba(255,255,255,.75);cursor:pointer;padding:0;line-height:0}
  .clear-btn svg{display:block;width:11px;height:11px}
  .clear-btn:hover{background:rgba(255,255,255,.22);color:#fff}
  .clear-btn.show{display:flex}
  .hot-list{
    position:absolute;top:calc(100% + 8px);left:0;right:0;z-index:200;
    margin:0;padding:8px;list-style:none;border-radius:14px;
    background:#191920;border:1px solid #2a2b37;
    box-shadow:0 18px 44px rgba(0,0,0,.55);
    display:none;flex-direction:column;gap:2px;
  }
  .hot-list.show{display:flex}
  .hot-list .hot-label{
    font-size:11px;letter-spacing:1px;color:var(--c-text-mut);
    padding:4px 10px 8px;text-transform:uppercase;
  }
  .hot-list .hot-item{
    display:flex;align-items:center;gap:8px;color:var(--c-text-dim);
    padding:7px 10px;border-radius:8px;cursor:pointer;font-size:14px;
    transition:background .12s,color .12s;
  }
  .hot-list .hot-item .hot-rank{
    flex:0 0 18px;text-align:center;font-size:12px;font-weight:700;
    font-style:italic;color:var(--c-text-mut);
  }
  .hot-list .hot-item.top .hot-rank{color:var(--c-brand)}
  .hot-list .hot-item .hot-txt{min-width:0;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
  .hot-list .hot-item:hover{background:rgba(255,255,255,.06);color:#fff}

  /* ---------- Catalog ---------- */
  .catalog-panel{
    display:flex;flex-direction:column;flex:1 1 auto;min-height:0;
  }
  .catalog-head{padding:14px 16px;border-bottom:1px solid var(--c-border);display:flex;justify-content:space-between;align-items:center;flex:0 0 auto}
  .catalog-head h3{margin:0;font-size:15px}
  .catalog-head .sw-name{font-size:12px;color:var(--c-text-mut)}
  .catalog-body{
    padding:6px 6px 12px;flex:1 1 auto;overflow-y:auto;overflow-x:hidden;
    scrollbar-width:thin;scrollbar-color:var(--c-border) transparent;
  }
  .catalog-body::-webkit-scrollbar{width:8px}
  .catalog-body::-webkit-scrollbar-thumb{background:var(--c-border);border-radius:8px}
  .catalog-body::-webkit-scrollbar-thumb:hover{background:#3a3a44}

  .chapter{margin:8px 6px;border:1px solid var(--c-border);border-radius:10px;overflow:hidden;background:var(--c-bg-soft)}
  .chapter-title{
    display:flex;align-items:center;gap:8px;cursor:pointer;user-select:none;
    font-size:15px;font-weight:700;color:var(--c-text);padding:9px 12px;margin:0;
    background:linear-gradient(90deg,rgba(245,197,24,.10),transparent);
    transition:background .15s;
  }
  .chapter-title:hover{background:linear-gradient(90deg,rgba(245,197,24,.18),transparent)}
  .chapter-title .caret{
    display:flex;align-items:center;justify-content:center;flex:0 0 auto;
    width:22px;height:22px;padding:5px;box-sizing:border-box;
    transition:transform .2s;margin-right:6px;
  }
  .chapter-title .caret::before{
    content:"";display:block;width:8px;height:8px;
    border-right:1.8px solid var(--c-text-dim);border-bottom:1.8px solid var(--c-text-dim);
    transform:rotate(45deg);transition:transform .2s;
  }
  .chapter.collapsed .caret::before{transform:rotate(-45deg)}
  .chapter.collapsed .chapter-title{opacity:.82}
  .chapter-content{padding:2px 4px 6px}
  .chapter.collapsed .chapter-content{display:none}

  .section-title{
    display:flex;align-items:center;font-size:12px;color:var(--c-accent);
    font-weight:700;letter-spacing:.4px;margin:12px 6px 8px 22px;text-transform:none;
  }
  .section-title::before{
    content:"";flex:none;width:14px;height:14px;margin-right:7px;
    background:
      linear-gradient(var(--c-accent),var(--c-accent)) 0 1px/14px 2px no-repeat,
      linear-gradient(var(--c-accent),var(--c-accent)) 0 6px/14px 2px no-repeat,
      linear-gradient(var(--c-accent),var(--c-accent)) 0 11px/10px 2px no-repeat;
  }
  .section-title::after{
    content:"";flex:1 1 auto;margin-left:10px;border-bottom:1px dashed rgba(245,197,24,.22);
  }
  .vlist{list-style:none;margin:0;padding:0}
  .vitem{
    display:flex;align-items:center;gap:10px;padding:8px 10px;margin:1px 3px;border-radius:8px;cursor:pointer;
    transition:background .15s,color .15s;border:1px solid transparent;
  }
  .vitem:hover{background:rgba(245,197,24,.08)}
  .vitem.active{background:rgba(245,197,24,.14);border-color:rgba(245,197,24,.4)}
  .vitem .code{font-size:12px;color:var(--c-text-mut);min-width:34px;font-variant-numeric:tabular-nums}
  .vitem.active .code{color:var(--c-brand)}
  .vitem .ttl{font-size:14px;color:var(--c-text);flex:1}
  .vitem .badge{
    font-size:10px;padding:2px 7px;border-radius:6px;background:rgba(240,169,59,.16);color:var(--c-warn);
    border:1px solid rgba(240,169,59,.3);white-space:nowrap;
  }
  .vitem .src{font-size:11px;color:var(--c-text-mut)}
  .vitem.active .badge{background:rgba(240,169,59,.24)}

  .empty-state{padding:40px 20px;text-align:center;color:var(--c-text-mut)}
  .empty-state .big{font-size:34px;margin-bottom:8px;opacity:.6}

  /* ---------- Footer ---------- */
  .foot{display:none}

  /* ---------- 移动端课程选择按钮 + 浮层（PC 隐藏） ---------- */
  .mobile-course-btn{display:none}
  .course-menu-mask{display:none;position:fixed;inset:0;background:rgba(0,0,0,.55);z-index:200;align-items:flex-start;justify-content:flex-end;padding:54px 15px 0}
  .course-menu-mask.show{display:flex}
  .course-menu-card{width:220px;background:#1a1a1d;border:1px solid #2a2a30;border-radius:12px;box-shadow:0 12px 40px rgba(0,0,0,.6);overflow:hidden}
  .course-menu-list{padding:6px;display:flex;flex-direction:column;gap:4px}
  .course-menu-list button{width:100%;text-align:left;padding:12px 14px;background:transparent;border:1px solid transparent;border-radius:8px;color:var(--c-text);font-size:14px;cursor:pointer;transition:all .15s}
  .course-menu-list button:hover{background:rgba(255,255,255,.06)}
  .course-menu-list button.active{background:linear-gradient(90deg,var(--c-brand),var(--c-brand-2));color:#1a1a1d;font-weight:600;border-color:transparent}


  /* ---------- Responsive ---------- */
  @media (max-width:980px){
    .app{height:100vh;overflow:hidden;padding:0 15px 0}
    .topbar{flex-direction:row;align-items:center;justify-content:space-between;gap:8px;padding:6px 0 4px;flex:0 0 auto}
    .topbar-left{width:auto;justify-content:flex-start;flex:0 0 auto}
    .topbar-left .logo{height:30px;margin:0}
    .topbar-right{width:auto;gap:6px;flex:0 0 auto}
    .topbar-right:empty{display:none}
    /* 移动端隐藏顶部 tabs（改用"选择课程"按钮） */
    .tabs{display:none !important}
    /* 移动端显示"选择课程"按钮 */
    .mobile-course-btn{display:flex;align-items:center;gap:6px;padding:7px 12px 7px 14px;background:transparent;border:1px solid var(--c-border);border-radius:999px;color:#fff;font-size:13px;cursor:pointer;flex:0 0 auto}
    .mobile-course-btn:active{border-color:var(--c-brand)}
    .mobile-course-btn .mc-label{font-weight:500}
    .mobile-course-btn .hamburger{font-size:11px;line-height:1;color:var(--c-brand);transition:transform .2s}
    .mobile-course-btn.open .hamburger{transform:rotate(180deg)}
    .main > .search{width:100%;flex:0 0 auto}
    .player-title{display:none}
    .main > .search input{padding:8px 36px 8px 36px;font-size:13px}
    .main > .search input::placeholder{font-size:12px}
    .main > .search > svg{left:11px;width:14px;height:14px}
    .main{display:flex;flex-direction:column;gap:12px;margin-top:8px;flex:1 1 auto;min-height:0}
    .main > .search{flex:0 0 auto}
    .player-col{flex:0 0 auto;overflow:visible}
    .player-wrap{display:block;height:auto;padding:0;margin:0 -15px;background:transparent;border:none;border-radius:0;box-shadow:none;overflow:visible}
    .nav-row{display:none}
    .player-meta{padding:0}
    .player-box{aspect-ratio:16/9;flex:0 0 auto;border-radius:0}
    .player-box video{object-fit:contain}
    input,select,textarea{font-size:16px !important}
    .right-col{flex:1 1 auto;min-height:0;overflow-y:auto;overscroll-behavior:contain}
    .catalog-panel{flex:0 0 auto;margin-bottom:20px}
    .catalog-head{padding:3px 16px}
    .catalog-body{overflow-y:visible;max-height:none}
  }