:root{--ink:#223b40;--muted:#78878b;--line:#e3e9e7;--bg:#f5f7f6;--green:#2c664d;color-scheme:light}*{box-sizing:border-box}body{margin:0;color:var(--ink);background:var(--bg);font:14px/1.5 system-ui,-apple-system,"Segoe UI",sans-serif;-webkit-font-smoothing:antialiased}button,input{font:inherit}button{cursor:pointer;transition:background .15s,color .15s}button,a{touch-action:manipulation;-webkit-tap-highlight-color:transparent}button:disabled{opacity:.4;cursor:default}button:focus-visible,a:focus-visible,input:focus-visible{outline:3px solid #71a68a;outline-offset:3px}.sr-only{position:absolute;width:1px;height:1px;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap}main{max-width:1520px;margin:auto;padding:0 24px 24px}.site-header{height:76px;display:flex;align-items:center;justify-content:space-between;gap:15px;margin-bottom:6px}.brand{display:flex;align-items:center;gap:10px;text-decoration:none;font-size:14px;font-weight:650;color:var(--ink)}.brand img{object-fit:contain}.brand small{display:block;font-size:11px;font-weight:400;color:var(--muted)}.site-header>span{font-size:12px;color:#8b9997}.classroom{display:grid;grid-template-columns:minmax(0,1fr) 350px;gap:24px;align-items:start;scroll-margin-top:15px}.lesson-main{min-width:0;border:1px solid var(--line);border-radius:12px;overflow:hidden;background:#fff}.player-wrap{position:relative;display:flex;align-items:center;justify-content:center;aspect-ratio:16/9;background:#10191e;overflow:hidden}.player-wrap video{display:block;width:100%;height:100%;object-fit:contain}.play-overlay{position:absolute;inset:0;margin:auto;width:68px;height:68px;display:grid;place-items:center;border:1px solid #ffffff80;border-radius:50%;color:#fff;background:#142b31da;backdrop-filter:blur(8px);box-shadow:0 4px 22px #0003}.play-overlay svg{margin-left:4px}.play-overlay:hover{background:#2c664df2}.play-overlay[hidden]{display:none}.player-toolbar{display:flex;align-items:center;justify-content:space-between;gap:10px;padding:10px 14px;border-bottom:1px solid var(--line);background:#fcfdfc}.seek-controls,.speed-control{display:flex;align-items:center;gap:5px}.player-toolbar button{min-height:36px;border:1px solid transparent;background:none;color:#718780;border-radius:6px;padding:6px 9px;font-size:12px}.player-toolbar button:hover{background:#edf2ef}.speed-control>span{font-size:11px;color:var(--muted);margin-right:7px}.speed-control button{font-weight:600;min-width:44px}.speed-control button[aria-pressed=true]{background:#e7f0e8;color:var(--green);border-color:#d7e5d9}.lesson-info{padding:22px 24px}.lesson-meta{display:flex;gap:9px;align-items:center;font-size:11px;color:#8a9797}.badge{color:var(--green);font-weight:550}.lesson-info h2{font-size:21px;line-height:1.4;font-weight:650;letter-spacing:-.5px;margin:10px 0 7px}.lesson-info p{font-size:13px;color:var(--muted);line-height:1.75;margin:0}.lesson-info #player-status{font-size:12px;color:#a85d34;margin-top:10px}#player-status:empty{display:none}.lesson-actions{display:flex;align-items:center;gap:18px;border-top:1px solid #eef1ef;margin-top:22px;padding-top:18px}.complete-button{border:1px solid #dce4df;background:white;color:#5b7770;border-radius:7px;padding:9px 12px;font-size:12px;min-height:40px}.complete-button:hover{background:#f1f6f2}.complete-button.done{background:#edf6ee;color:var(--green);border-color:#c5ddcc}.download-link{text-decoration:none;color:#899794;font-size:12px}.download-link:hover{color:var(--green)}.next-button{margin-left:auto;border:0;border-radius:7px;background:var(--green);padding:10px 14px;min-height:40px;color:#fff;font-size:12px}.next-button:hover:not(:disabled){background:#215139}.playlist-wrap{border:1px solid var(--line);border-radius:12px;overflow:hidden;background:#fff}.playlist-top{display:flex;align-items:center;justify-content:space-between;padding:20px 20px 13px}.playlist-top h2{margin:0;font-size:16px;font-weight:600}.result-count{font-size:11px;color:#94a09e}.filters{display:flex;flex-wrap:wrap;gap:4px;padding:0 16px 14px}.nav-item{border:1px solid transparent;background:none;border-radius:6px;color:#7b8c89;padding:7px 8px;min-height:34px;font-size:11px}.nav-item:hover{background:#f2f5f3}.nav-item.active{background:#eaf2eb;border-color:#dce9de;color:var(--green);font-weight:600}.search{display:flex;align-items:center;gap:8px;margin:0 18px 12px;padding:9px 11px;border:1px solid #e5ebe8;background:#f7f9f7;border-radius:7px;color:#92a19c}.search:focus-within{border-color:#89ae99}.search svg{fill:none;stroke:currentColor;stroke-width:1.6;flex-shrink:0}.search input{background:none;border:0;outline:none;width:100%;min-width:0;font-size:12px;color:var(--ink)}.search input::placeholder{color:#9ba8a4}.playlist{height:clamp(330px,calc(100vh - 360px),640px);overflow-y:auto;padding:0 9px 12px;scrollbar-width:thin;scrollbar-color:#d5dfd8 transparent;overscroll-behavior:contain}.playlist-group{padding:10px 12px 5px;font-size:10px;color:#9eaaa5}.lesson-row{display:flex;align-items:center;width:100%;gap:11px;text-align:left;border:1px solid transparent;border-radius:8px;padding:12px 10px;background:none;margin:2px 0}.lesson-row:hover{background:#f6f9f6}.lesson-row.selected{background:#edf4ed;border-color:#dfeadf}.lesson-num{display:grid;place-items:center;flex-shrink:0;width:33px;height:33px;border-radius:7px;font-size:10px;background:#f1f5f1;color:#91a199}.selected .lesson-num{background:var(--green);color:#fff}.finished:not(.selected) .lesson-num{background:#e9f3e9;color:var(--green)}.row-text{flex:1;min-width:0}.row-text strong{display:block;font-size:12px;font-weight:500;line-height:1.5;color:#5e7470}.selected .row-text strong{color:#315c42;font-weight:600}.row-text small{display:block;font-size:10px;color:#9da9a3;margin-top:4px}.row-arrow{font-size:20px;color:#8eb599}.empty{padding:15px;font-size:12px;color:var(--muted);line-height:1.8}.progress{border-top:1px solid #edf1ee;padding:16px 20px}.progress-track{height:4px;border-radius:4px;background:#eaf0eb;overflow:hidden}.progress-track span{display:block;width:0;height:100%;background:#78a983;transition:width .2s}.progress small{display:block;margin-top:8px;color:#9ba8a2;font-size:10px}footer{display:flex;justify-content:space-between;gap:12px;padding:23px 0 0;font-size:11px;color:#a0ada7}footer i{font-style:normal;padding:0 6px}
@media(max-width:1120px){.classroom{grid-template-columns:minmax(0,1fr) 310px;gap:18px}main{padding:0 20px 20px}.lesson-info{padding:20px}.lesson-actions{gap:12px}.complete-button,.next-button,.download-link{font-size:11px}.filters{padding:0 12px 12px;gap:2px}.nav-item{padding:7px;font-size:10px}.lesson-info h2{font-size:19px}.speed-control>span{display:none}}
@media(max-width:850px){.classroom{grid-template-columns:1fr;gap:20px}.playlist{height:390px}.nav-item{font-size:12px;padding:8px 11px}.row-text strong{font-size:13px}.row-text small{font-size:11px}.speed-control>span{display:inline}.lesson-info h2{font-size:21px}.complete-button,.next-button,.download-link{font-size:12px}}
@media(max-width:520px){main{padding:0 12px 20px}.site-header{height:65px;margin-bottom:5px;padding:0 3px}.brand{font-size:12px;gap:8px}.brand img{width:30px;height:30px}.brand small,.site-header>span{font-size:10px}.classroom{gap:16px;scroll-margin-top:12px}.lesson-main,.playlist-wrap{border-radius:10px}.player-wrap{aspect-ratio:4/3;max-height:64vh}.play-overlay{width:56px;height:56px}.play-overlay svg{width:25px;height:25px}.player-toolbar{padding:8px 10px;gap:5px}.speed-control>span{display:none}.speed-control button{min-width:42px}.lesson-info{padding:17px 16px}.lesson-info h2{font-size:18px}.lesson-info p{font-size:12px}.lesson-meta{font-size:10px}.lesson-actions{flex-wrap:wrap;gap:12px;margin-top:17px;padding-top:15px}.complete-button{font-size:11px;padding:8px 10px}.download-link{font-size:11px;margin-left:auto}.next-button{width:100%;font-size:12px;margin:0}.filters{padding:0 12px 12px;gap:2px}.nav-item{font-size:11px;padding:7px 10px}.playlist{height:370px}footer{display:block;font-size:10px;line-height:2;padding-left:4px}footer span{display:block}}
@media(prefers-reduced-motion:reduce){*{transition:none!important;scroll-behavior:auto!important}}