@import url('https://fonts.googleapis.com/css2?family=DM+Sans:wght@400;500;600;700&family=Space+Grotesk:wght@500;600;700&display=swap');:root{font-family:'DM Sans',Arial,sans-serif;color:#172440;background:#f4f7fc;font-size:16px;--navy:#162442;--purple:#5b45c8;--line:#dce3ef}*{box-sizing:border-box}body{margin:0}button,input{font:inherit}button{cursor:pointer}button:disabled{cursor:default}button:focus-visible,input:focus-visible,a:focus-visible{outline:3px solid #f1ae2b;outline-offset:3px}header{height:86px;background:var(--navy);color:white;display:flex;align-items:center;justify-content:space-between;gap:30px;padding:0 40px}.brand{display:flex;align-items:center;gap:13px;color:white;text-decoration:none;font-family:'Space Grotesk',Arial,sans-serif;font-size:1.2rem}.brand b{color:#b9aaff}.brand-mark{width:43px;height:43px;border-radius:11px;background:#b9aaff;color:var(--navy);display:grid;place-content:center;font-size:2.3rem}.overall{display:flex;align-items:center;gap:14px;font-size:.82rem;white-space:nowrap}.overall progress{width:180px;height:7px;border:0;border-radius:9px;overflow:hidden;background:#354363}.overall progress::-webkit-progress-bar{background:#354363}.overall progress::-webkit-progress-value{background:#b9aaff}.overall progress::-moz-progress-bar{background:#b9aaff}.shell{min-height:calc(100vh - 86px);display:grid;grid-template-columns:310px minmax(0,1fr);max-width:1500px;margin:auto}aside{background:white;border-right:1px solid var(--line);padding:35px 23px}.side-label,.eyebrow{font-size:.75rem;letter-spacing:1.7px;font-weight:700;color:#6650bb}aside h1{font-family:'Space Grotesk',Arial,sans-serif;font-size:1.45rem;margin:11px 7px 25px}.checkpoint-link{width:100%;display:flex;align-items:center;gap:13px;text-align:left;border:0;background:transparent;border-radius:10px;padding:12px 10px;color:#53627b}.checkpoint-link:hover{background:#f5f4fb}.checkpoint-link.active{background:#eeebfc;color:#36277e}.checkpoint-link>span:last-child{min-width:0}.checkpoint-link b,.checkpoint-link small{display:block}.checkpoint-link b{font-size:.87rem;line-height:1.35}.checkpoint-link small{font-size:.75rem;color:#748096;margin-top:3px}.checkpoint-icon{width:33px;height:33px;display:grid;place-content:center;flex-shrink:0;border-radius:9px;background:color-mix(in srgb,var(--accent) 13%,white);color:var(--accent);font-size:.82rem;font-weight:700}.active .checkpoint-icon{background:var(--accent);color:white}.side-tip{border-top:1px solid var(--line);margin-top:26px;padding:24px 8px;display:flex;gap:10px;color:#617089;font-size:.8rem;line-height:1.55}.side-tip span{color:#bd426a}.side-tip p{margin:0}.side-tip 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button.correct:not(.active){background:#dcf4ec;border-color:#b9e3d7;color:#12715c}.question-tabs button.wrong:not(.active){background:#fff1e0;border-color:#f1d6b3;color:#a25c13}.question-card{background:white;border:1px solid var(--line);border-top:4px solid var(--accent);border-radius:14px;padding:30px;box-shadow:0 8px 25px #263b6110}.question-meta{display:flex;justify-content:space-between;gap:15px;color:#6b7890;font-size:.73rem;letter-spacing:1.3px;font-weight:700}.instruction{color:#4c5c74;margin:28px 0 13px}.normal-expression,.zero-expression{min-height:150px;border-radius:11px;background-color:#f8faff;background-image:linear-gradient(#d5ddeb55 1px,transparent 1px),linear-gradient(90deg,#d5ddeb55 1px,transparent 1px);background-size:25px 25px;display:flex;align-items:center;justify-content:center;flex-wrap:wrap;gap:16px;padding:28px;font:600 clamp(1.7rem,4vw,3rem) 'Space Grotesk',Arial,sans-serif;font-variant-numeric:tabular-nums}.normal-expression input,.zero-expression input{width:155px;min-height:62px;border:0;border-bottom:4px solid var(--accent);background:#fff;color:var(--accent);padding:6px 10px;text-align:center;font-weight:700;border-radius:7px 7px 2px 2px}.normal-expression input:read-only,.zero-expression input:read-only{background:#e7f6f0;border-color:#16805f;color:#126a53}.operator{color:#67758b}.zero-expression{font-size:clamp(1.2rem,2.5vw,2rem);gap:20px}.zero-number{display:inline-flex;align-items:flex-start;white-space:nowrap}.zero-number .zero-run{position:relative;display:inline-block;color:#8c98aa;letter-spacing:2px;margin:0 5px;padding-bottom:35px}.zero-number b{color:var(--accent)}.zero-number .brace{position:absolute;bottom:23px;left:0;right:0;border-bottom:2px solid #738197;border-left:2px solid #738197;border-right:2px solid #738197;height:8px;border-radius:0 0 7px 7px}.zero-number small{position:absolute;bottom:0;left:50%;transform:translateX(-50%);text-align:center;color:#68758a;font:600 .78rem 'DM 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small{font-size:.68rem}.actions{gap:10px}.primary,.secondary,.hint-button{padding:11px 14px;font-size:.85rem}.result-grid{grid-template-columns:1fr}.results{padding:22px}}@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important}}