:root{--ink:#26374b;--muted:#6e7f90;--blue:#336fcc;--paper:#fff;--ground:#f1f6fb;--line:#d8e3ef;--red:#dd4352;font-family:-apple-system,BlinkMacSystemFont,"PingFang SC",sans-serif;color:var(--ink);background:var(--ground);font-size:14px}*{box-sizing:border-box}body{margin:0}header{max-width:1280px;margin:auto;padding:24px 32px;display:flex;justify-content:space-between;border-bottom:1px solid var(--line)}a{color:var(--blue);text-decoration:none}main{max-width:1280px;margin:auto;padding:32px}h1{font-family:"Kaiti SC",KaiTi,serif;font-size:36px;margin:8px 0 12px;font-weight:600;letter-spacing:1px}h2{font-size:20px;margin:0 0 12px}h3{font-size:15px;margin:22px 0 12px}p{line-height:1.8;margin:8px 0;color:var(--muted)}.eyebrow{font-size:12px;color:var(--blue);letter-spacing:2px}.intro{display:flex;justify-content:space-between;align-items:center;margin-bottom:30px;gap:20px}.button,.text-button,select,input{font:inherit}button,label.button,select{cursor:pointer}.button{display:inline-flex;align-items:center;justify-content:center;min-height:42px;border:1px solid var(--line);border-radius:8px;background:white;color:var(--ink);padding:10px 16px;gap:8px;white-space:nowrap}.primary{background:var(--blue);color:white;border-color:var(--blue)}.text-button{background:none;border:0;color:var(--blue);padding:12px}.button:hover{filter:brightness(.97)}button:disabled{opacity:.45;cursor:default}button:focus-visible,a:focus-visible,label:focus-within,input:focus-visible,select:focus-visible{outline:3px solid #91bbff;outline-offset:3px}input,select{background:white;border:1px solid var(--line);border-radius:6px;padding:10px;max-width:100%}.source{display:grid;grid-template-columns:1.3fr 1fr;background:#fff;border:1px solid var(--line);border-radius:12px;padding:24px;gap:32px}.source>div+div{border-left:1px solid var(--line);padding-left:32px}.source .button,.source select{margin:4px 4px 4px 0}.source label[for=step-count]{margin-left:10px}#reference-name{font-size:12px;display:inline-block;max-width:140px;overflow:hidden;text-overflow:ellipsis;white-space:nowrap;vertical-align:middle}#reference-preview{width:52px;height:52px;object-fit:contain;vertical-align:middle}.hint{font-size:12px;line-height:1.7}#status{min-height:24px;margin:20px 0;color:var(--blue)}.lesson{display:grid;grid-template-columns:260px 1fr;border:1px solid var(--line);border-radius:14px;overflow:hidden;background:#fff}.lesson aside{padding:24px;background:#f8fbff;border-right:1px solid var(--line)}.section-label{display:flex;align-items:baseline;justify-content:space-between;gap:20px}.section-label span{color:var(--muted);font:11px ui-monospace,monospace}.section-label h2{font-size:18px}#steps{display:grid;gap:6px}#steps button{display:flex;align-items:center;gap:14px;text-align:left;border:1px solid transparent;background:none;border-radius:7px;padding:13px 12px;font:inherit;color:var(--ink);cursor:pointer}#steps button span{font:12px ui-monospace,monospace;color:var(--muted)}#steps button[aria-current=step]{background:white;border-color:#b7cee9;box-shadow:0 3px 8px #243c6310;color:var(--blue)}#steps button[aria-current=step] span{color:var(--red)}.player{padding:24px 32px}.paper-heading{display:flex;justify-content:space-between;color:var(--muted);font-size:12px}.paper{display:grid;place-items:center;min-height:380px;padding:10px;background:#fff}.paper img{display:block;width:auto;max-width:100%;height:410px;object-fit:contain}.caption{display:flex;align-items:center;justify-content:space-between;border-top:1px solid var(--line);padding:18px 0 4px}.caption span{color:var(--muted);font:11px ui-monospace,monospace}.playback{display:flex;justify-content:space-between;gap:8px}.downloads{display:flex;justify-content:flex-end;gap:10px;margin-top:20px}.crop-editor{margin-top:48px}.crop-layout{display:grid;grid-template-columns:minmax(0,1fr) 280px;gap:28px;margin-top:18px}#crop-canvas{width:100%;height:auto;background:white;border:1px solid var(--line);border-radius:6px;cursor:crosshair}.crop-controls{background:white;padding:24px;border:1px solid var(--line);border-radius:10px;align-self:start}.crop-controls label{display:grid;gap:8px;font-size:12px;color:var(--muted)}.fields{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin:12px 0}.fields input{width:100%}.crop-controls .button{width:100%}footer{text-align:center;color:var(--muted);font-size:12px;padding:32px 0 0}[hidden]{display:none!important}@media(max-width:760px){header{padding:18px}main{padding:20px 16px}.intro{display:block}h1{font-size:28px}.intro>a{margin-top:12px}.source,.lesson,.crop-layout{grid-template-columns:1fr}.source{padding:18px;gap:18px}.source>div+div{padding:18px 0 0;border-left:0;border-top:1px solid var(--line)}.lesson aside{padding:18px;border-right:0;border-bottom:1px solid var(--line)}#steps{grid-template-columns:repeat(2,minmax(0,1fr))}#steps button{padding:10px 6px;font-size:12px;gap:8px}.player{padding:20px 16px}.paper img{height:350px}.paper{min-height:350px}.downloads{flex-wrap:wrap}.crop-controls{order:-1}.section-label{gap:8px}}

.instruction{font-size:16px;line-height:1.9;color:var(--ink);background:#f3f7fd;border-left:3px solid var(--blue);padding:16px 20px;margin:0 0 12px;white-space:pre-line}textarea{font:inherit;resize:vertical;max-width:100%;border:1px solid var(--line);border-radius:6px;padding:10px;color:var(--ink);line-height:1.7}.crop-controls label:has(textarea){margin-top:14px}

.lesson-body{display:grid;grid-template-columns:minmax(0,1fr) minmax(240px,.9fr);align-items:center;gap:28px;padding:16px 0 24px}.narration{border-left:1px solid var(--line);padding-left:24px}.narration .caption{border:0;padding:8px 0;display:block}.narration .caption h2{font-size:24px}.narration .instruction{padding:14px 0;background:none;border:0}.narration .text-button{padding-left:0;font-size:12px}.lesson-body .paper{min-height:380px}.lesson-body .paper img{max-height:410px;max-width:100%;height:auto;object-fit:contain}@media(max-width:850px){.lesson-body{grid-template-columns:1fr;gap:8px}.narration{border-left:0;border-top:1px solid var(--line);padding:18px 0 0}.lesson-body .paper img{height:350px;width:auto}.lesson-body .paper{min-height:350px}}

.quality-issues{white-space:pre-line;color:#8b4614;background:#fff4e5;border-left:3px solid #e6a34b;padding:12px;font-size:13px;line-height:1.7}