:root{color-scheme:light;--ink:#183543;--muted:#52656a;--teal:#187267;--mint:#eaf5ef;--amber:#f4be61;--paper:#faf8f2;--line:#d6dedb;--focus:#a84d05;--radius:18px;font-family:system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;color:var(--ink);background:var(--paper)}
*{box-sizing:border-box}body{margin:0}button,input,select{font:inherit}button,a,input,select,summary{-webkit-tap-highlight-color:transparent}a{color:inherit;text-underline-offset:.22em}button{cursor:pointer;border:1px solid var(--line);background:#fff;color:var(--ink);border-radius:10px;min-height:44px;padding:10px 16px;font-weight:650}button:hover{border-color:var(--teal);background:#f2f8f4}button:disabled{opacity:.55;cursor:default}button.primary{background:var(--ink);color:white;border-color:var(--ink)}button.primary:hover{background:#265b64}input,select{border:1px solid #819595;border-radius:8px;min-height:44px;padding:9px 10px;color:var(--ink);background:#fff;width:100%;max-width:100%}input[type=checkbox]{width:20px;min-height:20px}input[type=range]{padding:0}label{display:block;font-weight:650;font-size:.87rem}label small{display:block;font-weight:400;color:var(--muted);line-height:1.5;margin:4px 0}label input,label select{margin-top:6px}p{line-height:1.65;margin:0 0 12px}h1,h2,h3{line-height:1.15;margin:0}h2{font-size:1.65rem;letter-spacing:-.04em}h3{font-size:1.1rem}svg{display:block;width:100%;height:auto;overflow:visible}[hidden]{display:none!important}:focus-visible{outline:3px solid var(--focus);outline-offset:4px}.skip{position:absolute;left:12px;top:-100px;background:#fff;z-index:10;padding:12px}.skip:focus{top:10px}.masthead{display:flex;justify-content:space-between;align-items:center;gap:16px;border-bottom:1px solid var(--line);padding:16px max(24px,calc((100vw - 1280px)/2));background:#fff}.brand{display:flex;align-items:center;gap:8px;font-weight:750;text-decoration:none}.brand span{font-size:.8rem;font-weight:500;color:var(--muted);margin-left:12px;padding-left:12px;border-left:1px solid var(--line)}.masthead nav{display:flex;gap:22px;font-size:.9rem}.masthead nav a{min-height:44px;display:flex;align-items:center;text-decoration:none}main{max-width:1280px;padding:24px 28px;margin:auto}.intro{display:flex;justify-content:space-between;align-items:center;gap:25px;margin:4px 0 20px}.breadcrumb{display:flex;flex-wrap:wrap;gap:10px;color:var(--muted);font-size:.77rem;margin-bottom:20px}.breadcrumb a{text-decoration:none}.eyebrow{font-size:.72rem;font-weight:750;letter-spacing:.12em;color:var(--teal);margin-bottom:10px}h1{font-size:3.2rem;letter-spacing:-.06em}h1 span{display:block;font-size:1.4rem;font-weight:450;letter-spacing:-.025em;margin:6px 0 14px}.lead{font-size:1.05rem;max-width:650px}.intro-note{display:flex;align-items:center;gap:16px;max-width:310px;font-size:.82rem}.intro-note p{margin:0}.lab-symbol{font-size:3.7rem;color:var(--teal)}.safety-line{font-size:.77rem;color:var(--muted);border-top:1px solid var(--line);padding-top:12px}.safety-line span{font-size:1rem;margin-right:5px}.activity-nav{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin:24px 0 12px}.activity-nav button{text-align:left;padding:15px 18px;display:grid;grid-template-columns:38px 1fr;align-items:center;gap:3px 8px;border-radius:14px}.activity-nav button>span{grid-row:span 2;font-size:1.1rem;color:var(--teal)}.activity-nav strong{font-size:1rem}.activity-nav small{font-weight:400;color:var(--muted);font-size:.75rem}.activity-nav button[aria-pressed=true]{border:2px solid var(--teal);padding:14px 17px;background:var(--mint)}.session-line{display:flex;justify-content:space-between;align-items:center;gap:12px;margin-bottom:16px}.session-line p{margin:0;font-size:.75rem;color:var(--muted)}.session-line button{font-size:.78rem;background:transparent}.session-line span{background:var(--ink);color:white;border-radius:20px;padding:2px 7px;margin-left:6px}.mission{display:flex;align-items:flex-start;justify-content:space-between;gap:24px;margin:20px 0}.mission p{font-size:.89rem;max-width:700px;margin:10px 0 0}.mission select{width:270px;font-size:.8rem}.mission .eyebrow{margin:0 0 8px}.lab-grid{display:grid;grid-template-columns:minmax(0,1fr) 330px;gap:18px;align-items:start}.observation{position:relative;overflow:hidden;border-radius:var(--radius);background:linear-gradient(130deg,#153442,#275855);padding:20px 22px;color:#fff;min-height:330px}.observation::before{content:"";position:absolute;inset:0;background-image:linear-gradient(#ffffff08 1px,transparent 1px),linear-gradient(90deg,#ffffff08 1px,transparent 1px);background-size:30px 30px;pointer-events:none}.observation>*{position:relative}.view-head{display:flex;justify-content:space-between;align-items:center;gap:12px}.view-head h3{font-size:.9rem;font-weight:500}.view-head span{font-size:.7rem;border:1px solid #ffffff38;border-radius:20px;padding:5px 10px;white-space:nowrap}.bottle-row{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin:22px 0 14px;align-items:end}.bottle{color:white;border:1px solid #ffffff30;background:transparent;padding:12px 6px 10px;border-radius:12px;text-align:center}.bottle:hover{background:#ffffff0f;border-color:#bcebd4}.bottle[aria-pressed=true]{background:#ffffff0d;border:2px solid #f4be61;padding:11px 5px 9px}.bottle svg{max-width:145px;margin:auto}.bottle strong{display:block;margin-top:9px;font-size:.95rem}.bottle small{font-weight:400;color:#c5dfd6;font-size:.74rem}.glass{fill:#ecfff810;stroke:#d2ede6;stroke-width:2}.glass-rim{fill:none;stroke:#d2ede6;stroke-width:2}.liquid-clear{fill:#b7e9dd20}.liquid-yellow{fill:#edcc58d9}.liquid-green{fill:#63ba78d9}.liquid-blue{fill:#57a6e4d9}.graduation{stroke:#c8ded1;stroke-width:1;fill:none}.cap{fill:#f4be61}.shine{fill:none;stroke:#ffffff60;stroke-width:5;stroke-linecap:round}.svg-text{font-family:system-ui,sans-serif;fill:currentColor}.bench-note{margin:0;color:#c5dfd6;text-align:center;font-size:.7rem}.scene-caption{font-size:.77rem;color:#d2e7df;margin:12px 0 0}.measure-readout{display:flex;gap:14px;align-items:center;border-top:1px solid #ffffff35;margin-top:18px;padding-top:16px;min-height:70px}.measure-readout .reading{font-size:1.55rem;color:#ffdc96;letter-spacing:-.025em;line-height:1.25}.measure-readout p{font-size:.8rem;margin:0}.measure-readout small{display:block;font-size:.7rem;color:#d2e7df;margin-top:4px}.controls{padding:22px;background:white;border:1px solid var(--line);border-radius:var(--radius)}.controls h3{margin-bottom:14px}.controls p{font-size:.79rem;color:var(--muted)}.controls label{margin-bottom:14px}.test-buttons{display:grid;gap:8px}.test-buttons button{text-align:left;display:flex;justify-content:space-between;gap:10px;font-size:.77rem}.test-buttons button span{color:var(--muted);font-size:.7rem;font-weight:400;white-space:nowrap}.test-buttons button[data-done=true]{border-color:#b4cebf;background:#f1f7f2}.controls .primary{width:100%;margin-top:4px}.field-pair{display:grid;grid-template-columns:1fr 1fr;gap:12px}.checkline{display:flex;align-items:center;gap:9px;font-weight:500}.checkline input{margin:0}.notice{padding:14px 18px;border-radius:12px;background:#fff0d9;border:1px solid #e6c690;margin:12px 0;font-size:.84rem}.notice.success{background:var(--mint);border-color:#8ebb9f}.notice h3{margin-bottom:8px}.notice p:last-child{margin-bottom:0}.feedback{font-size:.85rem;line-height:1.6;margin:18px 0;padding:16px 18px;background:white;border:1px solid var(--line);border-left:4px solid var(--teal);border-radius:12px}.feedback.error{border-left-color:#bd5715}.feedback h3{margin:0 0 8px}.feedback p:last-child{margin-bottom:0}.hypotheses{padding:18px 20px;background:white;border:1px solid var(--line);border-radius:14px;margin:16px 0}.hypotheses h3{font-size:.9rem;margin-bottom:10px}.candidate-list{display:flex;flex-wrap:wrap;gap:8px;list-style:none;padding:0;margin:0}.candidate-list li{padding:6px 10px;border-radius:7px;background:var(--mint);font-size:.76rem}.candidate-list li.eliminated{background:#f4f1ec;color:#706961;text-decoration:line-through}.hypotheses p{font-size:.76rem;color:var(--muted);margin:10px 0 0}.journal{font-size:.78rem;margin:18px 0}.table-scroll{overflow:auto;max-width:100%}table{border-collapse:collapse;width:100%;font-size:.8rem;text-align:left}th,td{padding:10px 12px;border-bottom:1px solid var(--line);vertical-align:top}caption{text-align:left;padding:8px 0;font-weight:700}thead th{background:#edf3ef}td p{margin:0}.identification{background:white;border:1px solid var(--line);border-radius:14px;padding:20px;margin:16px 0}.identification h3{margin-bottom:12px}.label-row{display:grid;grid-template-columns:repeat(3,1fr);gap:12px;margin:12px 0}.identification>p{font-size:.8rem;color:var(--muted)}.layers{display:flex;flex-wrap:wrap;align-items:center;gap:10px;border-top:1px solid var(--line);padding-top:18px;margin-top:20px}.layers p{font-size:.8rem;margin:0 10px 0 0}.layers button{font-size:.76rem}.layers button[aria-pressed=true]{background:var(--mint);border-color:var(--teal)}.representations{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin-top:14px}.representation{padding:20px;border:1px solid var(--line);border-radius:var(--radius);background:#fff;min-width:0}.representation h3{font-size:1rem;margin:8px 0 12px}.representation p{font-size:.78rem}.representation .eyebrow{margin:0}.representation svg{max-height:215px;margin:10px auto}.micro-box{fill:#f3f8f4;stroke:#99b8a6;stroke-width:1}.micro-sugar{fill:#bc7390;stroke:#704255}.micro-acid{fill:#c0772d;stroke:#75411c}.micro-base{fill:#4d95b5;stroke:#2f5869}.micro-water{fill:#ddece9;stroke:#789b91}.micro-salt{fill:#64a792;stroke:#285d4e}.micro-label{font-size:12px;fill:#fff;font-weight:650}.micro-water+.micro-label{fill:var(--ink)}.equation{background:#f1f6f2;border-radius:9px;padding:14px;font-size:1.03rem!important;line-height:1.7;font-weight:700;overflow-wrap:anywhere}.symbol-values{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin:14px 0}.symbol-values div{border-left:2px solid #91b8a5;padding-left:10px}.symbol-values dt{color:var(--muted);font-size:.7rem;margin-bottom:5px}.symbol-values dd{margin:0;font-size:.95rem;font-weight:700}.replay{padding:20px;background:#fff;border:1px solid var(--line);border-radius:var(--radius);margin:18px 0}.replay h3{margin:12px 0 8px}.replay p{font-size:.84rem;max-width:760px}.replay-controls{display:flex;flex-wrap:wrap;align-items:center;gap:10px;margin:12px 0}.replay-controls span{font-size:.75rem;color:var(--muted);margin-left:auto}.explain-button{display:block;margin:18px 0;font-size:.8rem}.trial-scene{max-width:460px;margin:20px auto 8px}.trial-scene svg{max-height:235px}.big-reading{font-size:1.85rem!important;color:#ffdc96}.comparison{padding:20px;background:#eef6ef;border:1px solid #a6c4b0;border-radius:var(--radius);margin:16px 0}.comparison h3{margin-bottom:12px}.comparison>p{font-size:.8rem}.comparison .field-pair{grid-template-columns:1fr 1fr 1fr}.comparison-table{margin:14px 0}.comparison-table td:first-child{font-weight:650}.comparison label{margin:12px 0}.comparison-output{padding:14px;background:#fff;border-radius:10px;font-size:.84rem}.notebook{padding:18px 20px;background:#fff;border:1px solid var(--line);border-radius:var(--radius);margin:24px 0}.notebook summary{cursor:pointer;font-weight:750}.notebook-head{display:flex;gap:20px;align-items:center;justify-content:space-between;margin:16px 0}.notebook-head p{font-size:.8rem;max-width:650px;margin:0}.notebook-entry{display:flex;justify-content:space-between;gap:15px;align-items:center;border-top:1px solid var(--line);padding:12px 0}.notebook-entry p{font-size:.8rem;margin:0}.notebook-entry small{display:block;color:var(--muted);margin-top:4px}.notebook-entry button{font-size:.75rem}.understand{border-top:1px solid var(--line);margin-top:40px;padding-top:32px}.section-heading{margin-bottom:25px}.lesson-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:28px}.lesson-number{display:block;font-size:.78rem;color:var(--teal);margin-bottom:12px}.lesson-grid h3{max-width:260px;margin-bottom:14px}.lesson-grid p{font-size:.84rem;color:var(--muted)}.course-links{background:var(--mint);border-radius:14px;padding:20px 22px;display:flex;flex-wrap:wrap;align-items:center;gap:12px 22px;margin:24px 0}.course-links h3{flex-basis:100%;font-size:.9rem}.course-links a{font-size:.8rem;display:flex;gap:10px;align-items:center;min-height:44px;flex:1 1 230px}.model-notes{border-top:1px solid var(--line);padding:18px 0;font-size:.83rem}.model-notes summary{cursor:pointer;font-weight:700;min-height:28px}.model-notes p,.model-notes ul{margin-top:15px;max-width:900px}.model-notes li{line-height:1.7;margin:8px 0}.model-notes li p{margin:4px 0;color:var(--muted)}footer{display:flex;justify-content:space-between;gap:16px;margin-top:30px;padding-top:20px;border-top:1px solid var(--line);font-size:.78rem;color:var(--muted)}.load-note{font-size:.85rem}.pulse-once{animation:readout-in .35s ease-out}@keyframes readout-in{from{opacity:.3;transform:translateY(4px)}to{opacity:1;transform:translateY(0)}}
.lab-symbol{width:52px;min-width:52px;height:64px}
.micro-sugar{fill:#9c4f6f}.micro-acid{fill:#92521d}.micro-base{fill:#316f8a}.micro-salt{fill:#367660}
.controls>button:not(.primary){width:100%;margin-top:10px}
@media(min-width:1500px){main{padding-top:30px}}
@media(max-width:1000px){.lab-grid{grid-template-columns:minmax(0,1fr) 290px}.controls{padding:18px}.intro-note{max-width:220px}.lab-symbol{display:none}.mission h2{font-size:1.45rem}.mission select{width:230px}.label-row{grid-template-columns:1fr}.lesson-grid{gap:20px}.comparison .field-pair{grid-template-columns:1fr 1fr}.observation{padding:18px}.bottle-row{gap:8px}}
@media(max-width:740px){main{padding:18px 16px}.masthead{padding:12px 16px}.brand span{display:none}.masthead nav{gap:15px;font-size:.77rem}.intro{display:block}.intro-note{max-width:none;font-size:.74rem;margin-top:12px}.intro-note p br{display:none}.intro-note strong{display:block}.breadcrumb{font-size:.71rem;margin-bottom:18px}h1{font-size:2.7rem}h1 span{font-size:1.2rem}.lead{font-size:.95rem}.safety-line{font-size:.71rem}.activity-nav{gap:6px}.activity-nav button{padding:12px 8px;display:block}.activity-nav button[aria-pressed=true]{padding:11px 7px}.activity-nav button>span{display:block;font-size:.8rem;margin-bottom:6px}.activity-nav strong{font-size:.85rem}.activity-nav small{display:none}.session-line{align-items:flex-start}.session-line p{font-size:.68rem;max-width:65%}.session-line button{padding:8px 10px;font-size:.7rem;white-space:nowrap}.mission{display:block}.mission p{font-size:.83rem}.mission label{display:block;margin-top:14px}.mission select{width:100%}.lab-grid{grid-template-columns:1fr;gap:14px}.observation{padding:16px;min-height:280px}.view-head span{font-size:.65rem;padding:4px 8px}.bottle-row{margin:18px 0 12px;gap:8px}.bottle{padding:10px 4px 8px}.bottle[aria-pressed=true]{padding:9px 3px 7px}.bottle strong{font-size:.83rem}.bottle small{font-size:.67rem}.bottle svg{max-width:108px}.bench-note{font-size:.65rem}.measure-readout .reading{font-size:1.25rem}.measure-readout{margin-top:12px;gap:10px}.controls h3{font-size:1.02rem}.test-buttons{grid-template-columns:1fr 1fr;gap:8px}.test-buttons button{display:block;padding:10px;font-size:.74rem;line-height:1.4;min-height:62px}.test-buttons button span{display:block;margin-top:3px}.representations{grid-template-columns:1fr}.layers p{flex-basis:100%;margin:0}.label-row{gap:4px}.identification{padding:16px}.comparison .field-pair{grid-template-columns:1fr}.notebook-head{display:block}.notebook-head button{margin-top:12px}.lesson-grid{grid-template-columns:1fr;gap:18px}.lesson-grid h3{max-width:none}.lesson-grid article{border-bottom:1px solid var(--line);padding-bottom:12px}.understand h2{font-size:1.5rem}.symbol-values{gap:12px}.notebook-entry{align-items:flex-start}.notebook-entry button{flex:none}.notebook-entry p{font-size:.75rem}footer{flex-direction:column}.replay-controls span{flex-basis:100%;margin:0}.trial-scene{max-width:310px}.course-links{padding:16px}.feedback{padding:14px}.representation{padding:18px}.hypotheses{padding:16px}.candidate-list{gap:6px}.candidate-list li{font-size:.72rem}.big-reading{font-size:1.6rem!important}}
@media(prefers-reduced-motion:reduce){*,*::before,*::after{animation:none!important;scroll-behavior:auto!important;transition:none!important}}