:root{--ink:#163b40;--muted:#577075;--teal:#086b68;--mint:#def2eb;--paper:#f5f7f4;--line:#d9e4df;--gold:#ffd56b;--orange:#b35828}*{box-sizing:border-box}body{margin:0;background:var(--paper);color:var(--ink);font-family:ui-rounded,"Avenir Next",Avenir,system-ui,sans-serif;font-size:16px;line-height:1.55}button,input{font:inherit}button,a,input{-webkit-tap-highlight-color:transparent}button{cursor:pointer;touch-action:manipulation}button:focus-visible,a:focus-visible,input:focus-visible,summary:focus-visible{outline:3px solid #bd691e;outline-offset:4px}header{max-width:1200px;margin:auto;padding:24px 34px;display:flex;align-items:center;gap:24px;border-bottom:1px solid var(--line)}#brand{display:flex;align-items:center;gap:12px;color:var(--ink);text-decoration:none;margin-right:auto;line-height:1.25}#brand 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.done{background:var(--teal)}.round-dots .current{background:#d39230}.exercise{background:white;border:1px solid var(--line);border-radius:25px;padding:32px}.exercise h1{font-size:1.8rem;letter-spacing:-.6px;line-height:1.35;margin:10px 0}.instruction{font-size:1.06rem;margin-bottom:24px}.activity{background:#f5f8f5;border:1px solid #e2eae3;border-radius:17px;padding:26px;margin:22px 0;min-height:165px;display:flex;flex-direction:column;justify-content:center;align-items:center;gap:18px}.fraction{display:inline-flex;vertical-align:middle;flex-direction:column;text-align:center;line-height:1.2;min-width:25px;margin:0 5px;font-weight:750}.fraction>span:first-child{border-bottom:2px solid currentColor;padding:0 5px 3px}.fraction>span:last-child{padding:3px 5px 0}.equation{display:flex;align-items:center;justify-content:center;gap:13px;flex-wrap:wrap;font-size:1.65rem}.fraction-input{display:inline-flex;flex-direction:column;gap:5px}.fraction-input 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#e8c890}.feedback.success{background:#e2f3e9;border-color:#abd1b9}.feedback:empty{display:none}.feedback strong{display:block;margin-bottom:3px}.actions{display:flex;gap:12px;flex-wrap:wrap;align-items:center}.tip{border-left:3px solid #d7b467;padding:10px 16px;margin:15px 0;background:#fff9e9;border-radius:0 10px 10px 0}.choices{display:flex;flex-wrap:wrap;gap:10px;justify-content:center}.choice{background:white;border:2px solid #c9d8cf;padding:14px 19px;border-radius:13px;color:var(--ink);min-height:54px}.choice.selected{border-color:var(--teal);background:var(--mint)}.line-wrap{width:100%;overflow-x:auto;padding:8px 4px 15px}.numberline{width:100%;min-width:260px;display:block;height:145px;touch-action:pan-y}.numberline .tick{stroke:#49675f;stroke-width:1.5}.numberline text{font-family:inherit;font-size:16px;fill:var(--ink)}.line-controls{display:flex;align-items:center;justify-content:center;gap:18px;flex-wrap:wrap}.line-controls button{border:1px solid #b2cbbc;border-radius:10px;background:white;color:var(--teal);font-size:1.4rem;width:48px;height:45px}.line-controls output{font-size:1rem;min-width:120px;text-align:center}.line-help{font-size:.85rem;margin:0;text-align:center}.success-view{text-align:center;max-width:640px;margin:30px auto;background:white;border:1px solid var(--line);border-radius:26px;padding:38px}.badge{width:92px;height:92px;display:grid;place-items:center;margin:0 auto 24px;font-size:43px;background:#fff0bd;border-radius:28px;transform:rotate(-5deg)}.success-view .actions{justify-content:center}.learned{padding:20px;background:var(--mint);border-radius:15px;margin:25px 0;text-align:left}.learned p{margin:0}.confetti{position:fixed;top:-20px;pointer-events:none;width:9px;height:14px;animation:fall 1.8s ease-in forwards;z-index:10}@keyframes fall{to{transform:translateY(95vh) rotate(430deg);opacity:0}}footer{max-width:1132px;margin:40px auto 24px;padding:0 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h1{font-size:1.5rem}.equation{gap:8px;font-size:1.4rem}.exercise-head{flex-wrap:wrap}.cell{height:44px}.success-view{padding:28px 20px}.section-heading h2{font-size:1.35rem}.section-heading p{font-size:.8rem}.grid{gap:3px}}@media(prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important;scroll-behavior:auto!important}}
@media(max-width:480px){.numberline text{font-size:32px}}