:root{--ink:#17324d;--paper:#fff8e7;--white:#fffdf8;--orange:#b64029;--orange-fill:#f3b27b;--blue:#28768d;--blue-fill:#a3d4df;--teal:#087f7b;--red:#db342b;--line:#17324d26}
*{box-sizing:border-box}body{margin:0;color:var(--ink);background:linear-gradient(#17324d06 1px,transparent 1px),linear-gradient(90deg,#17324d06 1px,transparent 1px),var(--paper);background-size:28px 28px;font:16px/1.65 "PingFang SC","Microsoft YaHei",sans-serif}button,input,select{font:inherit}button{cursor:pointer;color:var(--ink);background:var(--white);border:1.5px solid var(--ink);border-radius:8px;padding:9px 15px;font-weight:700;min-height:44px}button:hover:not(:disabled){background:#f8edca}button:disabled{opacity:.4;cursor:default}button[aria-pressed=true],button[aria-current=step]{background:var(--ink);color:var(--white)}button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible,summary:focus-visible{outline:3px solid 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32px;font-weight:500}.utilities{display:flex;gap:8px}.utilities button{font-size:12px;padding:9px}.lab{background:var(--white);border:2px solid var(--ink);border-radius:14px;box-shadow:7px 7px #17324d13;overflow:hidden}.lab-heading{display:flex;justify-content:space-between;align-items:center;gap:15px;padding:22px 28px;border-bottom:1px solid var(--line)}h2{font-size:25px;line-height:1.45;margin:0}.lesson-tag{font-size:12px;background:#e9f2ea;border-radius:30px;padding:6px 13px;white-space:nowrap}.workbench{display:grid;grid-template-columns:minmax(0,1fr) 290px;min-height:380px}.scene{padding:24px 28px;min-width:0}.controls{background:#f5efdf;padding:24px;border-left:1px solid var(--line)}.controls h3{margin:0 0 14px;font-size:19px}.controls>button{width:100%;margin-top:12px}.small{font-size:13px;color:#526577}.controls p{margin:8px 0 16px}.ingredient{padding:16px 0;border-bottom:1px dashed var(--line)}.ingredient-heading{display:flex;align-items:center;justify-content:space-between;gap:10px;margin-bottom:12px}.ingredient h3{margin:0;font-size:17px}.orange-text{color:var(--orange)}.blue-text{color:var(--blue)}.stepper{display:inline-flex;align-items:center;gap:13px}.stepper button{padding:2px;width:44px;font-size:22px}.stepper output{font-weight:800;font-size:22px;min-width:1.4em;text-align:center}.cups{display:flex;flex-wrap:wrap;gap:6px;align-items:flex-end;min-height:68px}.cup{width:47px;height:65px;display:inline-block;flex-shrink:0;vertical-align:bottom}.cup svg{width:100%;height:100%;display:block}.cups.compact{gap:2px;min-height:39px}.compact .cup{width:27px;height:38px}.legend-note{font-size:12px;color:#526577;margin:0 0 12px}.equation{background:#faf0d4;border-radius:10px;padding:16px 20px;margin:20px 0 8px;text-align:center}.equation .caption{display:block;font-size:13px;margin-bottom:5px}.math{font-size:clamp(27px,3vw,39px);font-weight:800;line-height:1.4;letter-spacing:1px}.math.small-math{font-size:25px}.fraction{display:inline-flex;vertical-align:middle;flex-direction:column;text-align:center;line-height:1.1;min-width:.8em;font-size:.8em;margin:0 4px}.fraction>span:first-child{border-bottom:2px solid currentColor;padding:0 4px 3px}.fraction>span:last-child{padding-top:3px}.button-row{display:flex;flex-wrap:wrap;gap:8px;margin:12px 0}.button-row button{flex:1;white-space:nowrap}.question{margin:22px 0 0;border-top:1px dashed var(--line);padding-top:17px}.question h3{font-size:17px;margin:0 0 9px}.whole-highlight{outline:3px solid #d39c17;outline-offset:8px;border-radius:4px}.guide{display:flex;align-items:center;gap:15px;padding:14px 28px;background:#f7f1df;border-top:1px solid var(--line);min-height:102px}.guide img{object-fit:contain;flex-shrink:0}.guide 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.blue-text{margin-top:6px}.pack-type{font-size:11px;margin-bottom:3px}.divide-history{font-size:15px;line-height:1.8;margin:16px 0}.success{display:flex;gap:12px;align-items:center;justify-content:center;color:var(--red);font-weight:800;margin:12px 0}.success svg{width:64px;height:64px;stroke:currentColor;stroke-width:7;fill:none;stroke-linecap:round;stroke-linejoin:round;animation:check-pop .55s ease both}.success p{margin:0;font-size:20px}.success small{display:block;font-size:12px;font-weight:500;color:var(--ink)}.compare-lab{border-top:1px solid var(--line);padding:22px 28px}.compare-heading{display:flex;justify-content:space-between;align-items:center;gap:15px}.compare-heading h3{margin:0;font-size:18px}.compare-heading .button-row{margin:0}.compare-pair{display:grid;grid-template-columns:1fr 1fr;gap:20px;margin-top:16px}.mix-box{background:#f6f3ea;border-radius:8px;padding:14px}.mix-box h4{font-size:14px;margin:0 0 12px}.mix-track{display:flex;height:26px;overflow:hidden;border:1px solid var(--ink);border-radius:5px}.mix-track .juice{background:var(--orange-fill);border-right:1px solid var(--ink)}.mix-track .water{background:var(--blue-fill)}.mix-legend{display:flex;flex-wrap:wrap;justify-content:space-between;font-size:12px;gap:8px;margin-top:8px}.compare-feedback{font-weight:700;font-size:14px;margin:13px 0 0}.challenge-tabs{display:flex;gap:7px;padding:16px 28px 0;flex-wrap:wrap}.challenge-tabs button{font-size:13px}.challenge-header{display:flex;justify-content:space-between;align-items:center;gap:15px;margin-bottom:18px}.challenge-header h3{font-size:19px;margin:0}.score{font-size:13px;color:var(--teal);font-weight:700}.answer-form label{display:block;font-size:14px;font-weight:700;margin-bottom:12px}.answer-form input{width:70px;text-align:center;border:1.5px solid 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both}.motion-paused *{animation-play-state:paused!important}.motion-paused .entrance{animation:none}.shake{animation:shake .3s ease}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}[hidden]{display:none!important}@keyframes appear{from{opacity:0;transform:translateY(9px)}to{opacity:1;transform:translateY(0)}}@keyframes check-pop{0%{transform:scale(.4);opacity:0}70%{transform:scale(1.15)}100%{transform:scale(1);opacity:1}}@keyframes shake{25%{transform:translateX(-4px)}75%{transform:translateX(4px)}}
@media(max-width:1000px){.lesson-toolbar{align-items:stretch;flex-wrap:wrap}.steps{flex-basis:100%}.utilities{margin-left:auto}.workbench{grid-template-columns:minmax(0,1fr) 245px}.scene{padding:20px}.controls{padding:20px}.course-nav a{padding:8px;gap:7px;font-size:12px}}
@media(max-width:700px){.page-shell{width:calc(100% - 24px);padding-top:12px}.course-nav{grid-template-columns:repeat(2,minmax(0,1fr))}.hero{padding:22px 0}.hero-stamp{display:none}.hero p:last-child{font-size:14px}.steps{display:grid;grid-template-columns:repeat(2,minmax(0,1fr))}.steps button{font-size:14px}.utilities button{min-height:40px}.workbench{grid-template-columns:1fr}.controls{border-left:0;border-top:1px solid var(--line)}.lab-heading{padding:20px;align-items:flex-start}.lesson-tag{display:none}h2{font-size:21px}.scene{padding:20px 16px}.guide{padding:12px 16px}.guide p{font-size:14px}.page-controls button{font-size:13px;padding:9px 12px}.page-controls p{display:none}.compare-heading{display:block}.compare-heading .button-row{margin-top:12px}.compare-lab{padding:20px 16px}.compare-pair{gap:10px}.mix-box{padding:10px}.unit-model{gap:7px}.unit-box{padding:12px 8px;min-height:170px}.unit-arrow{font-size:11px}.unit-box .cup{width:31px;height:44px}.result-pair{gap:8px}.result-pair>div{padding:12px 6px}.concepts{grid-template-columns:1fr}.challenge-tabs{padding:16px 16px 0}.challenge-tabs button{flex:1;white-space:nowrap}.form-pair{align-items:stretch}.cup{width:39px;height:54px}.math{font-size:29px}.pack-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.pack{padding:9px}.pack .cup{width:23px;height:34px}}
.motion-paused *{animation:none!important}
button[aria-pressed=true]:hover:not(:disabled),button[aria-current=step]:hover:not(:disabled){background:var(--ink);color:var(--white)}
@media(prefers-reduced-motion:reduce){*,*::before,*::after{animation:none!important;transition:none!important;scroll-behavior:auto!important}}