:root{--navy:#15374b;--navy2:#244d63;--blue:#296281;--ink:#193247;--muted:#5b7383;--line:#dbe4ea;--pale:#f2f6f8;--white:#fff;--orange:#cf7e33;--shadow:0 10px 36px rgba(21,55,75,.07);--radius:18px}*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:#f6f8fa;color:var(--ink);font-family:Arial,Helvetica,sans-serif;line-height:1.55}button,input,textarea,select{font:inherit}button{cursor:pointer}button:disabled{opacity:.42;cursor:not-allowed}a{color:#145f83}a:hover{text-decoration:none}button:focus-visible,a:focus-visible,input:focus-visible,textarea:focus-visible,select:focus-visible{outline:3px solid #d69c45;outline-offset:3px}.skip-link{position:absolute;left:-10000px;top:10px;z-index:20;background:#fff;padding:10px}.skip-link:focus{left:10px}.shell{min-height:100vh;display:grid;grid-template-columns:268px minmax(0,1fr);grid-template-rows:72px 1fr}.topbar{grid-column:1/-1;position:sticky;top:0;z-index:11;display:flex;align-items:center;gap:18px;padding:10px 25px;background:#fff;border-bottom:1px solid var(--line)}.brand{border:0;background:transparent;padding:0;display:flex;align-items:center;gap:13px;text-align:left;color:inherit}.brand-mark{width:48px;height:48px;display:grid;place-items:center;border-radius:15px;background:var(--navy);color:#fff;font-size:29px;font-weight:700;letter-spacing:-2px}.brand-mark span{color:#e7a35f}.brand-text strong{display:block;letter-spacing:.13em;font-size:16px}.brand-text small{color:var(--muted);font-size:11px}.top-right{margin-left:auto;display:flex;align-items:center;gap:16px}.status-pill{font-size:11px;font-weight:700;letter-spacing:.07em;color:#85531c;background:#fff2dd;padding:7px 10px;border-radius:40px}.top-link{background:none;border:0;color:var(--navy2);font-weight:bold}.sidebar{border-right:1px solid var(--line);background:white;padding:28px 16px 22px;position:sticky;top:72px;height:calc(100vh - 72px);overflow:auto;display:flex;flex-direction:column;gap:14px}.nav-head{padding:0 12px;color:#6b8290;font-size:11px;letter-spacing:.17em;font-weight:700;display:flex;align-items:center;justify-content:space-between}.nav-item{display:flex;align-items:center;width:100%;gap:12px;padding:14px 11px;margin:3px 0;border:1px solid transparent;background:transparent;border-radius:13px;text-align:left;color:#445d6a}.nav-item:hover{background:#f1f5f7}.nav-item.active{background:#e9f2f6;border-color:#bcd5e1;color:var(--navy);font-weight:700}.nav-item.locked{opacity:.55}.nav-num{flex:0 0 30px;border:1px solid #bdcbd3;border-radius:10px;height:30px;display:grid;place-items:center;font-size:12px}.nav-item.complete .nav-num{background:#e8f6ef;color:#327a58;border-color:#b6dfca}.nav-txt{font-size:13px;line-height:1.3}.nav-txt small{display:block;margin-top:4px;color:#718a97;font-size:10px}.side-bottom{margin-top:auto;border-top:1px solid var(--line);padding:20px 12px}.sheet-link{display:block;font-size:13px;font-weight:700;text-decoration:none;margin-bottom:15px}.side-bottom p{font-size:11px;line-height:1.5;color:var(--muted)}.main{min-width:0;overflow-x:hidden}.content-width{max-width:990px;margin:0 auto;padding:40px 35px 90px}.eyebrow{letter-spacing:.14em;color:#4f7e98;text-transform:uppercase;font-weight:bold;font-size:11px;margin-bottom:12px}.hero{display:grid;grid-template-columns:1.4fr .6fr;gap:25px;padding:36px 38px;overflow:hidden;border-radius:22px;background:linear-gradient(135deg,#163d54,#275976);color:white;box-shadow:var(--shadow);position:relative}.hero:after{content:'DNA · RNA · PROTEIN';position:absolute;right:-25px;top:28px;transform:rotate(15deg);font-size:75px;font-weight:700;line-height:1.2;color:rgba(255,255,255,.045);width:350px;pointer-events:none}.hero h1{font-size:clamp(30px,4vw,48px);line-height:1.12;margin:12px 0 18px;letter-spacing:-.035em}.hero p{font-size:15px;color:#dceaf2;max-width:550px}.hero 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5px}.progress-label{font-size:13px;color:var(--muted)}.progress-label strong{color:var(--ink);font-size:21px;display:block}.progress-track{height:8px;background:#dfe7ec;border-radius:15px;overflow:hidden;width:50%}.progress-fill{height:100%;background:#4c947c;border-radius:15px;transition:width .2s}.section-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:15px;margin:12px 0 30px}.section-tile{text-align:left;min-height:151px;border:1px solid var(--line);border-radius:17px;background:#fff;padding:22px;box-shadow:var(--shadow);color:var(--ink)}.section-tile:hover:not(:disabled){border-color:#9fbdcb;background:#f9fcfd}.section-tile .top{display:flex;justify-content:space-between;align-items:center;margin-bottom:18px}.tile-index{font-size:14px;font-weight:700;color:#42718b}.tile-state{font-size:11px;color:#6d8693}.tile-state.good{color:#28805b}.section-tile strong{display:block;font-size:17px;line-height:1.35;margin-bottom:6px}.section-tile p{font-size:12px;color:var(--muted);margin:0}.page-head{margin-bottom:25px}.back{border:0;background:none;color:#34718f;padding:0;margin-bottom:17px;font-size:13px;font-weight:700}.page-head h1{font-size:clamp(26px,4vw,39px);line-height:1.2;letter-spacing:-.03em;margin:8px 0}.page-head p{color:var(--muted);font-size:14px;margin:10px 0 0}.step-controls{display:flex;gap:8px;align-items:center;flex-wrap:wrap;margin-top:18px}.step-chip{padding:7px 11px;min-width:36px;text-align:center;border:1px solid #d2e1e8;background:#fff;color:#456878;border-radius:10px;font-size:12px}.step-chip.current{background:#1c4d65;color:#fff;border-color:#1c4d65}.step-chip.done{background:#eaf7ee;color:#257051;border-color:#9dccae}.learning-card{border:1px solid var(--line);background:#fff;border-radius:20px;box-shadow:var(--shadow);padding:30px;margin:20px 0}.learning-card h2{font-size:22px;letter-spacing:-.02em;margin:0 0 12px}.learning-card h3{font-size:17px;margin:24px 0 10px}.learning-card p{font-size:15px;max-width:780px}.learning-card .step-meta{font-size:11px;color:#53819a;font-weight:bold;letter-spacing:.09em;margin-bottom:9px}.learn-text{background:#f5f8fa;padding:18px 20px;border-left:3px solid #7aa1b7;border-radius:0 10px 10px 0;margin:18px 0}.learn-text p{margin:0 0 9px}.learn-text p:last-child{margin-bottom:0}.visual{border:1px solid #e1e7ea;border-radius:14px;background:white;margin:20px 0;overflow:hidden}.visual img{display:block;width:100%;height:auto;max-height:560px;object-fit:contain}.visual figcaption{font-size:11px;color:#6a7e89;background:#f5f8fa;padding:10px 16px}.question{margin-top:26px;border-top:1px solid #e0e8ed;padding-top:20px}.question-title{font-size:18px;font-weight:700;margin:0 0 15px}.option{display:flex;gap:11px;align-items:flex-start;border:1px solid #d9e4e9;border-radius:11px;padding:13px 16px;margin:9px 0;cursor:pointer;font-size:14px}.option:hover{background:#f5f9fa}.option 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.btn{min-width:54px}.free-answer{width:100%;min-height:125px;resize:vertical;border-radius:11px;border:1px solid #c5d4dd;padding:14px;font-size:14px;color:var(--ink)}.smallnote{font-size:12px;color:#5e7888}.model-answer{background:#f1f6f8;border-radius:12px;padding:17px 19px;margin-top:15px}.model-answer p{margin:7px 0}.check-row{display:flex;align-items:flex-start;gap:8px;margin:8px 0;font-size:13px}.check-row input{width:18px;height:18px;accent-color:#367c93}.sheet-prompt{margin-top:22px;padding:23px 25px;border-radius:17px;border:1px solid #b7d5e3;background:#eef6fa}.sheet-prompt h3{margin:0 0 8px}.sheet-prompt p{font-size:13px}.sheet-prompt label{display:flex;gap:10px;margin:16px 0;font-size:13px;font-weight:bold;align-items:center}.sheet-prompt input{width:20px;height:20px;accent-color:#2a718f}.notice{padding:14px 18px;border-left:3px solid #e7aa5c;background:#fff8ed;border-radius:0 10px 10px 0;font-size:13px;margin:18px 0}.external-box{margin-top:15px;background:#f5f8fa;border-radius:12px;padding:13px 16px;font-size:12px}.toast{position:fixed;bottom:18px;right:18px;background:#153a4c;color:white;border-radius:10px;padding:13px 18px;box-shadow:var(--shadow);font-size:13px;opacity:0;pointer-events:none;transition:opacity .2s;z-index:30}.toast.show{opacity:1}.icon-button{border:0;background:none;font-size:22px;color:var(--navy)}.mobile-only{display:none}.nav-backdrop{display:none}.data-grid{width:100%;border-collapse:collapse;font-size:13px}.data-grid th,.data-grid td{padding:11px;border-bottom:1px solid #dce5ea;text-align:left}.data-grid thead{background:#edf3f6}.task-figure{position:relative}.task-figure img{width:100%;height:auto;display:block}.hotspots{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:10px;margin-top:12px}.hotspots label{display:flex;align-items:center;gap:8px;font-size:12px;border:1px solid #d4e2e9;border-radius:9px;padding:10px}.hotspots 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