:root{--paper:#f6f5f0;--white:#fff;--ink:#17342f;--muted:#52665e;--green:#235e47;--green-hover:#174632;--line:#d9e1d9;--soft:#eaf0e6;--yellow:#efd790;--red:#9f2929}*{box-sizing:border-box}body{background:var(--paper);color:var(--ink);margin:0;font-family:Arial,Helvetica,sans-serif;font-size:16px;line-height:1.5}a{color:var(--green);text-underline-offset:.25em}button,input,textarea{font:inherit}button{cursor:pointer}button:disabled{cursor:default;opacity:.55}button,a,input,textarea{-webkit-tap-highlight-color:transparent}:focus-visible{outline-offset:4px;outline:3px solid #936000}h1,h2,p{margin-top:0}h1{letter-spacing:-.045em;margin-bottom:1rem;font-size:clamp(2.2rem,4vw,3.8rem);line-height:1.12}h2{letter-spacing:-.025em;font-size:1.65rem;line-height:1.2}.page-width{max-width:1180px;margin-inline:auto;padding-inline:32px}.brand{letter-spacing:-.04em;color:var(--ink);align-items:center;gap:14px;font-size:1.25rem;font-weight:750;text-decoration:none;display:inline-flex}.brand-dot{color:var(--green);font-size:1.8rem}.eyebrow{text-transform:uppercase;letter-spacing:.14em;color:var(--green);margin-bottom:18px;font-size:.75rem;font-weight:700}.intro{color:var(--muted);font-size:1.125rem;line-height:1.65}.muted{color:var(--muted)}.small{font-size:.875rem}.panel{background:var(--white);border:1px solid var(--line);border-radius:22px;padding:32px}.button{border:1px solid #0000;border-radius:12px;justify-content:center;align-items:center;gap:12px;min-height:48px;padding:12px 22px;font-weight:600;text-decoration:none;transition:background .15s;display:inline-flex}.primary{background:var(--green);color:#fff}.primary:hover:not(:disabled){background:var(--green-hover)}.secondary{color:var(--ink);background:#fff;border-color:#b7c6bb}.secondary:hover:not(:disabled){background:var(--soft)}.ghost{color:var(--ink);background:0 0}.ghost:hover:not(:disabled){background:var(--soft)}.wide{width:100%}.text-button{color:var(--green);text-underline-offset:.2em;background:0 0;border:0;min-height:44px;padding:10px;text-decoration:underline}.text-link{padding-block:12px;font-size:.9rem;display:inline-block}.stack{flex-direction:column;gap:12px;display:flex}.compact{gap:4px}input:not([type=checkbox]),textarea{color:var(--ink);background:#fff;border:1px solid #9eafa3;border-radius:10px;width:100%;min-height:48px;padding:12px 14px}textarea{resize:vertical}select{font:inherit;color:var(--ink);background:#fff;border:1px solid #9eafa3;border-radius:10px;width:100%;min-height:48px;padding:12px 14px}summary{cursor:pointer;padding-block:12px}.section-title{margin-top:32px}.projection-fullscreen{align-self:center}label{font-weight:600}.error{color:var(--red);background:#fff0ed;border:1px solid #df9a91;border-radius:12px;max-width:640px;margin:20px auto 0;padding:16px}.error p{margin-bottom:8px}.badge{background:var(--soft);border:1px solid #c6d2c0;border-radius:999px;padding:6px 12px;font-size:.8rem;font-weight:600;display:inline-block}.skip-link{z-index:100;border:2px solid var(--green);background:#fff;padding:12px;position:fixed;top:-100px;left:12px}.skip-link:focus{top:12px}.sr-only{clip:rect(0,0,0,0);white-space:nowrap;border:0;width:1px;height:1px;margin:-1px;padding:0;position:absolute;overflow:hidden}.site-header{border-bottom:1px solid var(--line);justify-content:space-between;align-items:center;min-height:100px;display:flex}.classes-page{padding-top:48px;padding-bottom:40px}.page-intro{margin-bottom:28px}.demo-banner{color:#5c4720;background:#f5ead0;border:1px solid #e3cc9a;border-radius:12px;margin-bottom:32px;padding:12px 18px;font-size:.85rem}.class-grid{grid-template-columns:repeat(4,1fr);gap:20px;display:grid}.class-card{border:1px solid var(--line);background:#fff;border-radius:24px;flex-direction:column;min-height:360px;padding:24px;display:flex}.card-top{justify-content:space-between;align-items:center;gap:12px;margin-bottom:28px;display:flex}.grade-mark{background:#e7ead3;border-radius:16px;justify-content:center;align-items:center;width:52px;height:52px;font-size:1.5rem;font-weight:700;display:flex}.accent-1 .grade-mark{background:#ede1d4}.accent-2 .grade-mark{background:#dce8e8}.accent-3 .grade-mark{background:#e7dff0}.class-card h2{margin-bottom:14px;font-size:2.1rem}.card-skill{margin-bottom:6px;font-weight:600}.card-bottom{margin-top:auto;padding-top:22px}.card-bottom .text-link{text-align:center;display:block}.page-footnote{color:var(--muted);text-align:center;margin-top:36px;font-size:.85rem}.login-page{grid-template-columns:1.2fr 1fr;align-items:center;gap:80px;max-width:1240px;min-height:100vh;margin:auto;padding:60px 40px;display:grid}.login-story .brand{margin-bottom:70px}.login-story h1{font-size:clamp(2.6rem,5vw,4.7rem)}.login-panel{width:100%;max-width:460px;padding:42px}.login-panel .stack{margin-top:30px}.login-panel .button{margin-top:14px}.number-art{align-items:center;gap:10px;margin-block:34px;display:flex}.number-art span{font-size:2rem;font-weight:700}.number-art span:nth-child(odd){background:#e7ead3;border-radius:18px;padding:10px 18px;transform:rotate(-6deg)}.number-art span:last-child{background:var(--yellow);transform:rotate(5deg)}.demo-note{color:var(--muted);font-size:.8rem;line-height:1.7}.room{background:var(--paper);flex-direction:column;min-height:100dvh;padding:24px 40px;display:flex}.room-header{justify-content:space-between;align-items:center;gap:20px;display:flex}.room-header .eyebrow{margin-bottom:4px}.room-header h1{letter-spacing:-.025em;margin:0;font-size:1.4rem}.room-skill{color:var(--muted);margin-left:20px;font-size:.95rem;font-weight:400}.room-tools{align-items:center;gap:14px;display:flex}.challenge{text-align:center;flex:1;padding-top:clamp(30px,7vh,70px)}.challenge .eyebrow{color:var(--muted)}.equation{letter-spacing:-.04em;font-variant-numeric:tabular-nums;font-size:clamp(4rem,12vw,10rem);font-weight:700;line-height:1.2}.answer-slot{min-height:145px;padding-top:12px}.answer{color:var(--green);margin-bottom:6px;font-size:clamp(3rem,6vw,5rem);font-weight:700;line-height:1.1}.strategy{color:var(--muted);font-size:1.1rem}.thinking{color:var(--muted);margin-top:24px;font-size:1.2rem}.main-actions{justify-content:center;gap:16px;margin:10px 0 32px;display:flex}.main-actions .button{min-width:185px}.teacher-controls{text-align:center;border-top:1px solid var(--line);padding-top:24px}.control-row{flex-wrap:wrap;justify-content:center;align-items:center;gap:12px;display:flex}.level-options{flex-wrap:wrap;justify-content:center;align-items:center;gap:24px;margin-top:14px;display:flex}.check-label{align-items:center;gap:8px;min-height:44px;font-size:.9rem;font-weight:400;display:flex}.check-label input{accent-color:var(--green);width:20px;height:20px}.teacher-controls .small{margin-block:4px}.projection .teacher-controls,.projection .room-header .eyebrow,.projection .room-skill{display:none}.projection .challenge{flex-direction:column;justify-content:center;display:flex}.projection .equation{font-size:clamp(5rem,16vw,13rem)}.end-dialog{border:1px solid var(--line);max-width:min(580px,90vw);color:var(--ink);border-radius:20px;padding:32px}.end-dialog::backdrop{background:#0f231c80}.summary{max-width:980px;padding-top:70px;padding-bottom:50px}.summary-stats{grid-template-columns:repeat(4,1fr);gap:16px;margin:36px 0;display:grid}.summary-stats div{border:1px solid var(--line);background:#fff;border-radius:18px;padding:24px}.summary-stats dt{color:var(--muted);font-size:.85rem}.summary-stats dd{margin:12px 0 0;font-size:2rem;font-weight:700}.summary>.control-row{justify-content:flex-start;margin-top:28px}.history-page{padding-top:48px;padding-bottom:48px}.history-page .eyebrow{margin-top:24px}.history-list{flex-direction:column;gap:16px;padding:0;list-style:none;display:flex}.history-list li{justify-content:space-between;align-items:center;gap:24px;display:flex}.history-list h2{margin:12px 0}.history-list p:last-child{margin-bottom:0}@media (max-width:1050px){.class-grid{grid-template-columns:repeat(2,1fr)}.login-page{gap:40px}.summary-stats{grid-template-columns:repeat(2,1fr)}}@media (max-width:640px){.page-width{padding-inline:20px}.site-header{min-height:80px}.brand{font-size:1.05rem}.class-grid{grid-template-columns:1fr}.class-card{min-height:320px}.login-page{grid-template-columns:1fr;gap:20px;padding:30px 20px}.login-story .brand{margin-bottom:28px}.login-story h1{font-size:2.8rem}.number-art{display:none}.login-panel{max-width:none;padding:28px}.room{padding:20px 14px}.room-header{align-items:flex-start}.room-skill{margin:8px 0;display:block}.room-tools{flex-direction:column;gap:4px}.challenge{padding-top:30px}.main-actions{gap:8px}.main-actions .button{min-width:0;padding-inline:16px}.teacher-controls{padding-top:18px}.level-options{gap:4px}.summary{padding-top:36px}.summary-stats{gap:10px}.summary-stats div{padding:18px}.history-list li{flex-direction:column;align-items:flex-start}}@media (prefers-reduced-motion:reduce){*,:before,:after{scroll-behavior:auto!important;transition:none!important;animation:none!important}}.equation .math-instruction{letter-spacing:normal;margin-bottom:1rem;font-size:clamp(1.1rem,2.5vw,2rem);font-weight:500}