:root{color:#17343a;font-synthesis:none;text-rendering:optimizelegibility;--teal:#066a75;--teal-dark:#034f58;--teal-soft:#dceff0;--ink:#17343a;--muted:#60777b;--line:#d6e2e1;--surface:#fff;background:#eef5f4;font-family:Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,Segoe UI,sans-serif}*{box-sizing:border-box}html{scroll-behavior:smooth}body{min-width:320px;min-height:100vh;margin:0}button,a{font:inherit}button{color:inherit}button:focus-visible,a:focus-visible{outline-offset:3px;outline:3px solid #f0a83b}.app-shell{min-height:100vh;padding-bottom:76px}.topbar{background:var(--surface);border-bottom:1px solid var(--line);z-index:10;justify-content:space-between;align-items:center;height:64px;padding:0 20px;display:flex;position:sticky;top:0}.brand{color:var(--ink);align-items:center;gap:10px;font-weight:800;text-decoration:none;display:inline-flex}.brand-mark{color:#fff;background:var(--teal);border-radius:11px;place-items:center;width:34px;height:34px;display:grid}.avatar{cursor:pointer;background:#f2c9a5;border:0;border-radius:50%;width:40px;height:40px;font-weight:800}main{width:min(100%,940px);margin:0 auto;padding:18px 16px 48px}.hero-panel{background:var(--teal);color:#fff;border-radius:22px;gap:22px;padding:24px;display:grid;box-shadow:0 16px 34px #066a752e}.eyebrow{text-transform:uppercase;letter-spacing:.11em;margin:0 0 7px;font-size:.72rem;font-weight:800}h1,h2,p{margin-top:0}h1{letter-spacing:-.04em;margin-bottom:10px;font-size:clamp(1.8rem,7vw,3rem);line-height:1.05}.lede{color:#d9eff1;max-width:58ch;margin-bottom:0}.validation{color:var(--ink);border-radius:15px;flex-direction:column;gap:3px;padding:14px 16px;display:flex}.validation.valid{background:#e8f6e9}.validation.invalid{background:#ffe3df}.validation span{font-size:.88rem}.lesson-tabs{grid-template-columns:1fr;gap:10px;margin:18px 0;display:grid}.lesson-tabs button{text-align:left;border:1px solid var(--line);background:var(--surface);cursor:pointer;border-radius:16px;flex-direction:column;gap:3px;min-height:70px;padding:14px 16px;display:flex}.lesson-tabs button.active{color:var(--teal-dark);border:2px solid var(--teal);background:var(--teal-soft)}.lesson-tabs span{font-weight:750}.lesson-tabs small{color:var(--muted)}.lesson{background:var(--surface);border:1px solid var(--line);border-radius:22px;overflow:hidden}.lesson-header{border-bottom:1px solid var(--line);justify-content:space-between;align-items:flex-start;gap:16px;padding:22px;display:flex}.lesson-header h2{margin-bottom:8px;font-size:clamp(1.35rem,5vw,1.8rem)}.lesson-header p:last-child{color:var(--muted);margin:0}.count{background:var(--teal-soft);min-width:42px;height:42px;color:var(--teal-dark);border-radius:14px;flex:none;place-items:center;font-weight:850;display:grid}.task-list{gap:8px;padding:10px;display:grid}.task-card{border:1px solid var(--line);border-radius:15px;overflow:hidden}.task-summary{text-align:left;cursor:pointer;background:#fff;border:0;grid-template-columns:34px 1fr 30px;align-items:center;gap:12px;width:100%;padding:14px;display:grid}.task-summary:hover{background:#f7fbfa}.task-number{background:var(--teal-soft);width:32px;height:32px;color:var(--teal-dark);border-radius:10px;place-items:center;font-weight:850;display:grid}.task-copy{flex-direction:column;gap:3px;display:flex}.task-copy small{color:var(--teal);font-weight:800}.task-copy strong{line-height:1.3}.chevron{color:var(--teal);text-align:center;font-size:1.4rem;font-weight:900}.task-detail{color:var(--muted);padding:0 16px 16px 62px}.statement{color:var(--ink);background:#f3f7f6;border-radius:12px;padding:12px;font-weight:700}details{margin:14px 0}summary{cursor:pointer;color:var(--teal-dark);font-weight:750}details p{margin:10px 0 0}.source-link{background:var(--teal);color:#fff;border-radius:12px;flex-direction:column;gap:2px;padding:13px 15px;text-decoration:none;display:flex}.source-link small{color:#d9eff1}.bottom-nav{border:1px solid var(--line);z-index:20;-webkit-backdrop-filter:blur(10px);backdrop-filter:blur(10px);background:#fffffff5;border-bottom:0;border-radius:20px 20px 0 0;grid-template-columns:1fr 1fr;width:min(100%,940px);height:68px;display:grid;position:fixed;bottom:0;left:50%;transform:translate(-50%)}.bottom-nav a,.bottom-nav button{color:var(--muted);background:0 0;border:0;flex-direction:column;justify-content:center;align-items:center;gap:2px;font-size:.82rem;text-decoration:none;display:flex}.bottom-nav .active{color:var(--teal);font-weight:800}.bottom-nav button:disabled{opacity:.45}@media (width>=700px){main{padding:28px 24px 70px}.hero-panel{grid-template-columns:1.5fr .8fr;align-items:end;padding:34px}.lesson-tabs{grid-template-columns:1fr 1fr}.lesson-header{padding:28px}.task-list{padding:14px}}@media (width<=520px){.task-detail{padding-left:16px}.task-summary{grid-template-columns:32px 1fr 24px;gap:9px}}@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}}