:root{--ink:#172033;--muted:#5e6b82;--blue:#2563eb;--line:#dbe4f0;--paper:#fff}*{box-sizing:border-box}body{margin:0;background:#f6f8fc;color:var(--ink);font:16px/1.6 system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif}.shell{width:min(1080px,calc(100% - 32px));margin:0 auto;padding:48px 0}.eyebrow{font-weight:800;letter-spacing:.1em;font-size:.75rem;color:var(--blue);margin:0}.lead{color:var(--muted);max-width:720px}.home h1{font-size:clamp(2rem,5vw,3.4rem);line-height:1.15;margin:.2rem 0}.search{display:grid;gap:6px;max-width:520px;margin:28px 0 8px;font-weight:700}.search input{font:inherit;padding:11px 13px;border:1px solid #b8c5d8;border-radius:9px}.result-count{color:var(--muted);margin:0 0 16px}.lesson-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(235px,1fr));grid-auto-rows:116px;gap:14px;padding:0;list-style:none;margin:0}.lesson-grid li{min-width:0}.lesson-grid a{display:flex;width:100%;height:100%;align-items:center;text-decoration:none;color:var(--ink);background:var(--paper);border:1px solid var(--line);border-radius:14px;padding:14px 18px;box-shadow:0 5px 18px #1720330b}.lesson-grid a:hover{border-color:var(--blue);color:var(--blue);transform:translateY(-2px)}.lesson-no{color:var(--blue);font-weight:800;font-size:.85rem;display:block}.topbar{background:var(--ink);color:#fff}.topbar .shell{padding:18px 0;display:flex;justify-content:space-between;gap:16px;align-items:center}.topbar a{color:#bfdbfe;text-decoration:none;font-weight:700}.topbar strong{font-size:.9rem}.lesson h1{line-height:1.2;margin:.3rem 0 8px}.lesson>p{color:var(--muted)}.plain-answer{font-size:1.08rem}.panel{background:var(--paper);border:1px solid var(--line);border-radius:16px;padding:24px;margin-top:24px;box-shadow:0 10px 30px #1720330a}.panel h2{margin-top:0}.instruction{color:var(--muted);margin-top:-8px}.workspace{display:grid;grid-template-columns:minmax(0,1fr) minmax(280px,.85fr);gap:18px}.preview-title{font-size:1rem;margin:0 0 8px}.preview-frame{width:100%;min-height:370px;border:1px solid var(--line);border-radius:11px;background:#fff}.editor-label{display:block;font-weight:800;margin-bottom:8px}.html-editor{display:block;width:100%;min-height:310px;resize:vertical;border:1px solid #b8c5d8;border-radius:10px;padding:13px;background:#0f172a;color:#dbeafe;font:13px/1.55 ui-monospace,SFMono-Regular,Menlo,monospace}.row{display:flex;flex-wrap:wrap;gap:10px;margin-top:12px}button{border:0;border-radius:8px;padding:10px 14px;font:inherit;font-weight:700;cursor:pointer;background:var(--blue);color:#fff}button:hover{background:#1d4ed8}.secondary{background:#e8eef8;color:#1e3a67}.takeaways{padding-left:22px}.takeaways li+li{margin-top:10px}.source{margin-top:16px;color:var(--muted);font-size:.9rem}@media(max-width:760px){.shell{padding:28px 0}.topbar .shell{align-items:flex-start;flex-direction:column}.workspace{grid-template-columns:1fr}.panel{padding:18px}.lesson-grid{grid-auto-rows:108px}}