:root{--primary: #2563eb;--primary-dark: #1d4ed8;--bg: #f5f7fa;--card: #ffffff;--text: #1f2937;--muted: #6b7280;--border: #e5e7eb;--danger: #dc2626;--success: #16a34a;--shadow: 0 1px 3px rgba(0, 0, 0, .08), 0 1px 2px rgba(0, 0, 0, .04)}*{box-sizing:border-box}html,body{margin:0;padding:0;height:100%;font-family:-apple-system,BlinkMacSystemFont,Segoe UI,PingFang SC,Microsoft YaHei,sans-serif;background:var(--bg);color:var(--text)}#app{min-height:100%}button{font-family:inherit;cursor:pointer;border:none;border-radius:8px;padding:8px 14px;font-size:14px;background:var(--primary);color:#fff;transition:background .15s,opacity .15s}button:hover{background:var(--primary-dark)}button:disabled{opacity:.5;cursor:not-allowed}button.ghost{background:#fff;color:var(--text);border:1px solid var(--border)}button.ghost:hover{background:#f3f4f6}button.danger{background:var(--danger)}button.danger:hover{background:#b91c1c}input,select{font-family:inherit;font-size:14px;padding:8px 10px;border:1px solid var(--border);border-radius:8px;outline:none;background:#fff}input:focus,select:focus{border-color:var(--primary)}.topbar{display:flex;align-items:center;justify-content:space-between;padding:14px 24px;background:var(--card);border-bottom:1px solid var(--border);position:sticky;top:0;z-index:10}.topbar h1{font-size:18px;margin:0;display:flex;align-items:center;gap:8px}.topbar .links{display:flex;gap:10px;align-items:center}.container{max-width:1040px;margin:0 auto;padding:24px}.muted{color:var(--muted);font-size:13px}.section-title{font-size:16px;font-weight:600;margin:24px 0 12px}.login-wrap{min-height:100vh;display:flex;align-items:center;justify-content:center;background:linear-gradient(135deg,#eef2ff,#f5f7fa)}.login-card{background:var(--card);padding:32px;border-radius:16px;box-shadow:var(--shadow);width:360px;text-align:center}.login-card h2{margin:0 0 6px}.login-card .hint{color:var(--muted);font-size:13px;margin-bottom:18px}.login-card input{width:100%;margin-bottom:12px;text-align:center}.login-error{color:var(--danger);font-size:13px;min-height:18px;margin-top:4px}.course-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(320px,1fr));gap:16px}.course-card{background:var(--card);border:1px solid var(--border);border-radius:14px;padding:16px;box-shadow:var(--shadow)}.course-card .head{display:flex;align-items:center;justify-content:space-between}.course-card .head .name{font-weight:600;font-size:15px}.course-card .head .count{color:var(--muted);font-size:12px}.course-card .actions{display:flex;gap:8px;margin-top:12px;flex-wrap:wrap}.file-list{margin-top:12px;border-top:1px dashed var(--border);padding-top:10px;display:flex;flex-direction:column;gap:6px}.file-row{display:flex;align-items:center;justify-content:space-between;gap:8px;padding:6px 8px;border-radius:8px;background:#f9fafb}.file-row .fname{flex:1;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;font-size:13px}.file-row .meta{color:var(--muted);font-size:12px;margin-right:8px}.file-row .ops{display:flex;gap:6px}.file-row .ops button{padding:5px 10px;font-size:12px}.empty{color:var(--muted);text-align:center;padding:40px 0}.create-bar{display:flex;gap:8px;margin-bottom:8px}.create-bar input{flex:1}.progress-mask{position:fixed;inset:0;background:#00000059;display:flex;align-items:center;justify-content:center;z-index:50}.progress-box{background:#fff;padding:24px 28px;border-radius:14px;width:320px;text-align:center}.progress-box .bar{height:8px;background:#e5e7eb;border-radius:4px;overflow:hidden;margin-top:12px}.progress-box .bar>div{height:100%;background:var(--primary);width:0%;transition:width .2s}.teacher-list{display:grid;grid-template-columns:repeat(auto-fill,minmax(280px,1fr));gap:16px}.teacher-course{background:var(--card);border:1px solid var(--border);border-radius:14px;padding:16px;box-shadow:var(--shadow)}.teacher-course h3{margin:0 0 10px;font-size:15px}.teacher-file{display:flex;align-items:center;justify-content:space-between;padding:10px 12px;border-radius:10px;background:#f9fafb;margin-bottom:8px}.teacher-file .tname{flex:1;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}.teacher-file .play-btn{background:var(--success)}.teacher-file .play-btn:hover{background:#15803d}.player{position:fixed;inset:0;background:#000;z-index:100;display:flex;flex-direction:column;overflow:hidden}.player .topbar-player{position:absolute;top:0;left:0;right:0;z-index:5;display:flex;align-items:center;justify-content:space-between;padding:10px 16px;color:#fff;background:linear-gradient(to bottom,#0009,#0000);transition:opacity .3s}.player .topbar-player .title{font-size:14px;opacity:.9}.player .topbar-player .ctrls{display:flex;gap:8px}.player .topbar-player .ctrls button{padding:6px 10px;font-size:13px;background:#ffffff26}.player .topbar-player .ctrls button:hover{background:#ffffff4d}.player .topbar-player .ctrls button.active{background:var(--primary)}.player .stage{flex:1;display:flex;align-items:center;justify-content:center;position:relative;cursor:none;-webkit-user-select:none;user-select:none}.player.drawing .stage{cursor:crosshair}.player .stage img{max-width:100%;max-height:100%;object-fit:contain;pointer-events:none;-webkit-user-drag:none}.player .arrow{position:absolute;top:50%;transform:translateY(-50%);background:#ffffff1f;color:#fff;border:none;width:54px;height:54px;border-radius:50%;font-size:22px;z-index:4}.player .arrow:hover{background:#ffffff47}.player .arrow.prev{left:16px}.player .arrow.next{right:16px}.player .page-indicator{position:absolute;bottom:14px;left:50%;transform:translate(-50%);color:#fff;background:#00000080;padding:4px 14px;border-radius:20px;font-size:13px;z-index:5}.player .thumbs{position:absolute;left:0;right:0;bottom:0;z-index:6;display:flex;gap:8px;padding:10px;overflow-x:auto;background:#000000a6;transform:translateY(100%);transition:transform .25s}.player .thumbs.show{transform:translateY(0)}.player .thumbs img{height:84px;border-radius:6px;cursor:pointer;opacity:.6;border:2px solid transparent;flex:none}.player .thumbs img.active{opacity:1;border-color:var(--primary)}.player .laser{position:absolute;width:16px;height:16px;border-radius:50%;background:radial-gradient(circle,#ff3b3b,red 40%,#f000 70%);pointer-events:none;transform:translate(-50%,-50%);opacity:0;z-index:7;box-shadow:0 0 12px 4px #ff0000b3}.player .laser.active{opacity:1}.player.hide-ui .topbar-player{opacity:0;pointer-events:none}.player.hide-ui .arrow,.player.hide-ui .page-indicator{opacity:0}.player.hide-ui:hover .topbar-player{opacity:1;pointer-events:auto}.player.hide-ui:hover .arrow,.player.hide-ui:hover .page-indicator{opacity:1}.player.black{background:#000}.player.black .stage,.player.black .thumbs{display:none}.speed-select{background:#ffffff26;color:#fff;border:none}.speed-select option{color:#000}.player #anno{position:absolute;z-index:3;pointer-events:none;touch-action:none}.player.drawing #anno{pointer-events:auto;cursor:crosshair}.player .annotate{position:absolute;left:12px;top:50%;transform:translateY(-50%);z-index:8;display:flex;flex-direction:column;gap:10px;background:#141414d9;padding:10px 8px;border-radius:12px;transition:opacity .3s}.player .anno-row{display:flex;flex-direction:column;gap:6px;align-items:center}.player .anno-row+.anno-row{border-top:1px solid rgba(255,255,255,.15);padding-top:10px}.player .anno-row button{width:34px;height:34px;border-radius:8px;font-size:15px;background:transparent;color:#fff;padding:0;display:flex;align-items:center;justify-content:center}.player .anno-row button:hover{background:#ffffff2e}.player .anno-row button.active{background:var(--primary)}.player .anno-row button i{border-radius:50%;background:#fff;display:block}.player .swatch{width:22px!important;height:22px!important;border-radius:50%!important;border:2px solid rgba(255,255,255,.6)}.player .swatch.active{outline:2px solid #fff;outline-offset:1px}.player .custom-swatch{position:relative;width:22px;height:22px;font-size:13px;cursor:pointer;display:flex;align-items:center;justify-content:center;border-radius:50%;background:#ffffff26}.player .custom-swatch input{position:absolute;inset:0;opacity:0;cursor:pointer}.player.hide-ui .annotate{opacity:0;pointer-events:none}.player.hide-ui:hover .annotate{opacity:1;pointer-events:auto}.player.black #anno,.player.black .annotate{display:none}