:root{--navy:#182139;--teal:#167c7c;--cream:#f8f4eb;--coral:#e75c50;--yellow:#f7c85b;--muted:#667085;font-family:"Microsoft YaHei","PingFang SC",Arial,sans-serif;color:var(--navy);background:#101626}
*{box-sizing:border-box}body{margin:0;overflow:hidden}button,a{touch-action:manipulation}button{font:inherit;cursor:pointer}button:disabled{opacity:.34;cursor:default}button:focus-visible,a:focus-visible{outline:3px solid var(--yellow);outline-offset:3px}[hidden]{display:none!important}
#lesson-player{height:100vh;height:100dvh;display:flex;flex-direction:column;background:#101626}.player-topbar{display:flex;align-items:center;justify-content:space-between;gap:24px;min-height:68px;flex-shrink:0;padding:11px 24px;background:var(--cream);color:var(--navy)}.home-link{color:var(--teal);text-decoration:none;font-size:15px;white-space:nowrap}.home-link:hover{text-decoration:underline}.course-heading{min-width:0;flex:1}.course-heading h1{margin:0;font-size:21px;line-height:1.35;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}.course-heading p{margin:4px 0 0;font-size:12px;line-height:1.3;color:var(--muted)}#course-duration{font-size:14px;color:var(--teal);white-space:nowrap}
#slide-stage{position:relative;flex:1;min-height:0;width:100%;overflow:hidden;outline:none;display:flex;align-items:center;justify-content:center}#slide-image{display:block;width:100%;height:100%;object-fit:contain;object-position:center;background:transparent;user-select:none}#slide-stage.is-loading #slide-image{opacity:.2}#stage-message{position:absolute;inset:0;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:13px;padding:30px;color:var(--cream);background:#101626a6;text-align:center}#stage-message p{margin:0;line-height:1.6}#stage-message-title{font-size:24px;font-weight:600}#stage-message-detail{font-size:16px;max-width:650px;color:#b8c6d9}#stage-message button,.message-home{font:inherit;font-size:16px;border:1px solid #7ea9a4;border-radius:6px;background:var(--teal);color:white;padding:9px 20px;text-decoration:none}
#player-controls{display:flex;align-items:center;justify-content:space-between;gap:18px;min-height:58px;flex-shrink:0;padding:9px 22px;background:#101626;color:var(--cream);font-size:14px}.controls-group{display:flex;align-items:center;gap:8px}#player-controls button,.control-link{font:inherit;display:inline-flex;align-items:center;justify-content:center;text-decoration:none;min-height:36px;border:1px solid #455064;border-radius:5px;padding:6px 13px;background:transparent;color:#f3f4f6;white-space:nowrap}#player-controls button:hover,.control-link:hover{background:#263348}#player-controls button.primary{background:var(--teal);border-color:var(--teal)}#page-counter{color:#c4ccda;font-size:15px;font-variant-numeric:tabular-nums;white-space:nowrap}#player-progress{height:3px;flex-shrink:0;background:#333b50;width:100%}#player-progress i{display:block;height:100%;width:0;background:var(--yellow);transition:width .15s}
#presentation-shortcuts{display:flex;gap:7px;position:fixed;right:14px;top:12px;z-index:35;opacity:.7;transition:opacity .18s}#presentation-shortcuts button{font:inherit;min-height:33px;border:1px solid #68768b;border-radius:6px;background:#101626e8;color:#f3f4f6;padding:5px 10px;font-size:12px;line-height:1.4}#presentation-shortcuts:hover,#presentation-shortcuts:focus-within{opacity:1}
body.presentation #lesson-player{position:fixed;inset:0;width:100%;height:100dvh}body.presentation #slide-stage{position:absolute;inset:0;flex:none;width:100%;height:100%}body.presentation .player-topbar{position:fixed;top:0;left:0;right:0;z-index:25;min-height:68px;background:#f8f4ebed;transition:transform .2s,opacity .2s}body.presentation #player-controls{position:fixed;bottom:0;left:0;right:0;z-index:30;background:#101626f2;transition:transform .2s,opacity .2s}body.presentation #player-progress{position:fixed;bottom:0;left:0;z-index:31;height:3px;transition:opacity .2s}body.presentation.controls-hidden .player-topbar{transform:translateY(-110%);opacity:0;pointer-events:none}body.presentation.controls-hidden #player-controls{transform:translateY(110%);opacity:0;pointer-events:none}body.presentation.controls-hidden #player-progress,body.presentation.controls-hidden #presentation-shortcuts{opacity:0}body.presentation.controls-hidden #presentation-shortcuts:hover,body.presentation.controls-hidden #presentation-shortcuts:focus-within{opacity:1}
dialog{border:0;border-radius:10px;background:var(--cream);color:var(--navy);padding:24px 28px;max-width:min(760px,94vw);max-height:90dvh;box-shadow:0 20px 100px #0008}dialog::backdrop{background:#0d152add}.dialog-header{display:flex;gap:20px;justify-content:space-between;align-items:center;margin-bottom:22px}.dialog-header h2{font-size:24px;line-height:1.35;margin:0;color:var(--teal)}.dialog-header p{font-size:14px;margin:7px 0 0;color:var(--muted)}.dialog-header button{border:0;border-radius:5px;background:var(--navy);color:white;font-size:15px;white-space:nowrap;padding:9px 15px}dialog>p{font-size:18px;line-height:1.8}dialog .dialog-note{font-size:15px;color:var(--muted)}.solid-button{border:0;border-radius:6px;padding:11px 18px;background:var(--teal);color:white;font-size:17px}.shortcut-list p{display:flex;align-items:center;flex-wrap:wrap;gap:8px;margin:16px 0;font-size:16px}.shortcut-list p span{margin-left:auto;color:var(--teal)}kbd{font:inherit;display:inline-block;border:1px solid #cbd2d1;border-bottom-width:3px;padding:5px 9px;border-radius:5px;background:#fffdf8;font-size:14px}
#slide-drawer{position:fixed;inset:0 0 0 auto;margin:0;width:min(930px,96vw);max-width:96vw;height:100vh;height:100dvh;max-height:100dvh;border-radius:10px 0 0 10px;overflow-y:auto}#slide-drawer .dialog-header{position:sticky;top:-24px;z-index:2;background:var(--cream);padding:10px 0 15px;border-bottom:1px solid #d4dcd8}#thumbnail-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:17px}#thumbnail-grid button{display:block;padding:7px;border:2px solid transparent;border-radius:7px;background:#eee9de;color:var(--navy);min-width:0}#thumbnail-grid button[aria-current=true]{border-color:var(--teal);background:#e0eeea}#thumbnail-grid img{display:block;aspect-ratio:16/9;width:100%;height:auto;object-fit:contain;background:#182139}#thumbnail-grid span{display:block;margin-top:7px;font-size:14px;font-variant-numeric:tabular-nums}#player-toast{position:fixed;bottom:78px;left:50%;transform:translateX(-50%);z-index:50;max-width:min(650px,92vw);padding:11px 20px;border:1px solid #667085;border-radius:7px;background:#182139f5;color:white;text-align:center;font-size:15px;line-height:1.6}
@media(max-width:860px){.player-topbar{gap:12px;padding:10px 14px;min-height:62px}.course-heading h1{font-size:18px}.course-heading p{font-size:11px}#course-duration{display:none}#player-controls{gap:8px;padding:8px 10px;font-size:12px}.controls-group{gap:5px}#player-controls button,.control-link{padding:6px 9px;min-height:34px}#page-counter{font-size:13px}#help-button{display:none}#thumbnail-grid{gap:12px}}
@media(max-width:570px){.player-topbar{gap:10px;padding:9px 10px}.home-link{font-size:12px}.course-heading h1{font-size:16px}.course-heading p{display:none}#player-controls{flex-wrap:wrap;justify-content:center;row-gap:6px;padding:8px;font-size:12px}#page-counter{order:3;font-size:12px;flex-basis:100%;text-align:center}.controls-group{gap:4px}#player-controls button,.control-link{padding:5px 8px;min-height:31px}.control-link{font-size:11px}#thumbnail-grid{grid-template-columns:repeat(2,minmax(0,1fr));gap:10px}dialog{padding:18px}.dialog-header h2{font-size:20px}#slide-drawer .dialog-header{top:-18px}.shortcut-list p span{margin-left:0;flex-basis:100%}}
@media(prefers-reduced-motion:reduce){*{transition:none!important}}