:root{color-scheme:light;--ink:#182943;--muted:#43556b;--line:#c8d7e5;--paper:#fffdf7;--mint:#d9f5e9;--blue:#deedff;--peach:#ffe8d5;--focus:#ffe56c;--body:Nunito,system-ui,sans-serif;--display:Fredoka,Nunito,system-ui,sans-serif;--bn:"Baloo Da 2","Noto Sans Bengali",sans-serif}
*{box-sizing:border-box}html{scroll-behavior:smooth}body{margin:0;background:#eef4f7;color:var(--ink);font:600 17px/1.45 var(--body)}button,input{font:inherit}button{cursor:pointer}button:focus-visible,a:focus-visible,input:focus-visible{outline:4px solid var(--focus);outline-offset:3px}a{color:inherit}.bn{font-family:var(--bn);word-break:keep-all;line-height:1.6}
.topbar{display:flex;align-items:center;gap:16px;padding:12px max(18px,calc((100vw - 1060px)/2));background:#16243b;color:#fff}.back{display:inline-flex;min-height:44px;align-items:center;padding:7px 12px;border:1px solid #a9bed1;border-radius:12px;text-decoration:none}.brand{flex:1;font:600 22px var(--display)}.language-button{min-height:44px;border:1px solid #fff;border-radius:12px;background:#fff;color:#173245;padding:7px 14px;font-weight:900}
main{max-width:1060px;margin:auto;padding:20px 18px 60px}.hero,.path,.workspace{border:1px solid var(--line);border-radius:24px;background:var(--paper);box-shadow:0 6px 18px #233e5a12}.hero{padding:28px 30px 22px;background:linear-gradient(140deg,#ffffff 25%,#e2f8ed 100%)}.eyebrow{margin:0 0 5px;color:#176a55;font-size:13px;font-weight:1000;letter-spacing:.06em}.hero h1{margin:0;font:600 clamp(30px,5vw,48px)/1.06 var(--display)}.hero>p:not(.eyebrow){max-width:760px;margin:10px 0 0;color:var(--muted)}.track-tabs{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:10px;margin-top:24px}.track-tab{min-height:82px;display:flex;align-items:center;justify-content:center;gap:10px;border:2px solid #abc4d3;border-radius:16px;background:#fff;color:var(--ink);font-weight:1000;text-align:left}.track-tab[aria-selected=true]{background:#183e52;color:#fff;border-color:#183e52}.track-icon{font:600 31px var(--display)}.track-names{display:flex;flex-direction:column}.track-names small{font:700 14px/1.2 var(--bn)}.scope-note{padding:10px 13px;border-radius:12px;background:#f5f8fa;font-size:14px}
.path{margin-top:18px;padding:22px}.section-head{display:flex;align-items:end;justify-content:space-between;gap:12px}.section-head h2{margin:0;font:600 30px var(--display)}.path-progress{margin:0;color:#315b69;font-weight:900;text-align:right}.lesson-list{display:grid;gap:10px;margin-top:16px}.path-module{border:1px solid #bed4df;border-radius:17px;background:#f8fbfd;overflow:hidden}.module-summary{display:flex;align-items:center;justify-content:space-between;gap:12px;padding:13px 16px;cursor:pointer;list-style:none}.module-summary::-webkit-details-marker{display:none}.module-summary::before{content:'▸';color:#176f67;font-size:19px}.path-module[open] .module-summary::before{content:'▾'}.module-summary strong{flex:1;font:600 22px var(--display)}.module-count{font-size:13px;color:#3e5968}.module-cards{display:grid;grid-template-columns:repeat(auto-fit,minmax(175px,1fr));gap:10px;padding:0 13px 13px}.lesson-card{min-height:118px;padding:14px;border:2px solid #ccdae5;border-radius:16px;background:#fff;text-align:left;color:var(--ink);display:flex;flex-direction:column;gap:3px}.lesson-card[aria-pressed=true]{border-color:#167f75;background:#e3faf1}.lesson-card:hover{border-color:#167f75}.lesson-number{font-size:13px;color:#276c61;font-weight:1000}.lesson-title{font:600 21px/1.18 var(--display)}.lesson-sub{font:700 13px var(--bn);line-height:1.3}.lesson-status{margin-top:auto;color:#3e5968;font-size:13px}.stretch{display:inline-block;border-radius:7px;background:#fff0bf;color:#654300;padding:1px 6px;font-size:12px;font-weight:1000}
.workspace{margin-top:18px;padding:24px 28px}.work-head{display:flex;align-items:start;justify-content:space-between;gap:12px}.work-head h2{margin:3px 0;font:600 33px/1.15 var(--display)}.work-intro{max-width:720px;margin:8px 0 16px;color:var(--muted)}.step-pill{border-radius:999px;background:#e2edf3;padding:6px 12px;font-weight:900;white-space:nowrap}.source{font-size:13px;color:#56707d}.model-frame{border:2px solid #bcd8d2;border-radius:20px;background:#f7fcf8;min-height:178px;padding:18px;overflow:auto}.model-caption{margin:0 0 9px;color:#315d5a;font-size:14px;font-weight:900}.model-inner{display:flex;flex-wrap:wrap;align-items:stretch;gap:10px}.model-group,.share-box{min-width:64px;min-height:64px;border:2px solid #6cafa0;border-radius:15px;background:#fff;padding:8px}.group-label{display:block;text-align:center;color:#3b6b6a;font-size:12px;font-weight:900}.dots{display:flex;flex-wrap:wrap;justify-content:center;gap:4px;max-width:110px}.dot{display:inline-block;width:15px;height:15px;border-radius:50%;background:#299b81;box-shadow:inset -2px -2px 0 #1d6d5e;animation:pop .26s ease both}.array-model{display:grid;gap:4px;align-content:start}.array-row{display:flex;gap:4px}.array-row .dot{background:#597bdc;box-shadow:inset -2px -2px 0 #36509d}.jump-line{display:flex;align-items:end;gap:3px;overflow:auto;padding:12px 2px}.jump{min-width:42px;display:flex;flex-direction:column;text-align:center;font-weight:900}.jump-arc{height:27px;border:3px solid #ff9658;border-bottom:0;border-radius:50% 50% 0 0}.jump-point{height:9px;width:9px;margin:2px auto;border-radius:50%;background:#3b587d}.pool{display:flex;flex-wrap:wrap;gap:4px;max-width:440px;align-content:start}.pool .dot{background:#f4a163;box-shadow:inset -2px -2px 0 #ba6b35}.pool-wrap{display:flex;flex-direction:column;gap:5px}.share-boxes{display:flex;flex-wrap:wrap;gap:8px}.share-box .dots{min-height:22px}.frac-bar{display:grid;min-width:200px;max-width:500px;width:100%;height:72px;overflow:hidden;border:2px solid #4e6e91;border-radius:16px;background:#fff}.frac-part{border-right:2px solid #4e6e91;background:#fff}.frac-part:last-child{border-right:0}.frac-part.shaded{background:#ffac71}.frac-row{display:flex;flex-direction:column;gap:8px;width:min(100%,500px)}.frac-label{font-size:14px;font-weight:900}.frac-set{display:flex;flex-wrap:wrap;gap:8px}.set-part{display:flex;flex-wrap:wrap;max-width:130px;gap:4px;border:2px dashed #8ba9bb;border-radius:12px;padding:8px}.set-part.shaded{background:#ffe4ce;border-color:#d37540}.set-part .dot{width:13px;height:13px}.model-equation{margin:12px 0 0;font:600 25px var(--display)}.lesson-step{margin:14px 0;padding:12px 15px;border-radius:14px;background:#e6f5ff;color:#254464;font-weight:900}.work-actions{display:flex;flex-wrap:wrap;gap:10px;margin-top:17px}.primary,.secondary,.quiet{min-height:48px;border-radius:13px;padding:10px 17px;font-weight:1000}.primary{border:2px solid #155f59;background:#176f67;color:#fff}.secondary{border:2px solid #4a77a0;background:#e1effe;color:#183b5d}.quiet{border:2px solid #b2c4d3;background:#fff;color:#2a4c61}.primary:hover,.secondary:hover,.quiet:hover{filter:brightness(.95)}.question{margin:16px 0;font:600 clamp(22px,3.5vw,30px)/1.25 var(--display)}.answer-line{display:flex;flex-wrap:wrap;align-items:end;gap:9px;margin-top:16px}.answer-line label{display:flex;flex-direction:column;gap:5px;font-weight:900}.answer-input{width:min(100%,290px);min-height:52px;border:2px solid #648797;border-radius:12px;background:#fff;color:var(--ink);font:900 24px var(--body);padding:6px 12px}.feedback{min-height:26px;margin:10px 0 0;font-weight:900}.feedback.good{color:#116347}.feedback.try{color:#8c461c}.answer-guide{margin-top:14px;border-left:5px solid #55a6bd;padding:10px 14px;background:#eaf7fc}.answer-guide p{margin:2px 0}.result-score{font:600 50px var(--display);color:#126a5c}.parent-note{margin:17px 4px 0;font-size:13px;color:#4b5d6d}
.frac-bar.winner{outline:4px solid #158f70;outline-offset:3px}
.example-label{margin:14px 0 9px;font-weight:1000;color:#214e68}.example-explain{margin:7px 0 0;color:#2b5262}.watch-card{margin-top:17px;padding:12px 15px;border-radius:14px;border-left:5px solid #ecaa4f;background:#fff6e8}.watch-card strong{font:600 21px var(--display)}.watch-card p{margin:4px 0}.sandbox{margin-top:19px;padding:17px;border:2px solid #a6c7d6;border-radius:18px;background:#f3fbff}.sandbox h3{margin:0;font:600 26px var(--display)}.sandbox>p{margin:6px 0 12px}.play-controls{display:flex;flex-wrap:wrap;gap:10px;margin-bottom:12px}.play-control{display:flex;align-items:center;gap:7px;padding:7px 10px;border:1px solid #aac7d8;border-radius:12px;background:#fff}.play-label{margin-right:4px}.stepper{width:42px;height:42px;border:2px solid #326e82;border-radius:10px;background:#e1f2fc;color:#16495b;font-size:25px;font-weight:900}.play-value{min-width:23px;text-align:center;font-size:22px}.play-equation{margin:11px 0 0!important;font:600 25px var(--display)}.partition-model{display:flex;flex-direction:column;gap:7px}.place-blocks{display:flex;flex-wrap:wrap;gap:5px;max-width:580px}.ten-rod,.one-block{display:inline-flex;align-items:center;justify-content:center;border:2px solid #3d7792;border-radius:8px;background:#95c6e6;color:#173b53;font-size:13px;font-weight:1000}.ten-rod{width:51px;height:30px}.one-block{width:25px;height:30px;background:#ffcc91;border-color:#c7783d}.partition-result{font:600 23px var(--display)}.fraction-line{display:flex;align-items:center;width:min(100%,650px);min-height:91px;border-top:4px solid #416787;margin-top:29px}.line-tick{flex:1;text-align:center;position:relative;min-width:0}.line-tick:last-child{flex:0}.tick-dot{position:absolute;top:-46px;left:0;transform:translateX(-50%);font-size:27px;color:#315f80}.line-target .tick-dot{color:#e57330}.tick-label{position:absolute;top:12px;left:0;transform:translateX(-50%);font-size:13px;font-weight:900;white-space:nowrap}
.challenge-source{display:inline-block;margin:8px 0 0;padding:4px 10px;border-radius:999px;background:#e6f2ff;color:#264e6c;font-size:13px;font-weight:900}
.brand.bn,.hero h1.bn,.module-summary strong.bn,.lesson-title.bn,.work-head h2.bn,.sandbox h3.bn,.track-names strong.bn{font-family:var(--bn);line-height:1.32}.lesson-title.bn{font-size:20px;font-weight:800}.track-names strong.bn{font-size:19px;font-weight:800}.lesson-sub:not(.bn){font-family:var(--body)}
@keyframes pop{from{opacity:.45;transform:translateY(4px) scale(.8)}to{opacity:1;transform:none}}@media(prefers-reduced-motion:reduce){*,*::before,*::after{animation:none!important;transition:none!important;scroll-behavior:auto!important}}
@media(max-width:690px){main{padding:12px 12px 50px}.hero,.path,.workspace{padding:18px;border-radius:19px}.track-tabs{gap:5px}.track-tab{min-height:75px;padding:6px;gap:4px;flex-direction:column;text-align:center;font-size:13px}.track-icon{font-size:25px}.track-names small{font-size:12px}.module-cards{grid-template-columns:repeat(2,minmax(0,1fr));gap:6px;padding:0 7px 7px}.lesson-card{min-height:112px;padding:10px}.lesson-title{font-size:18px}.module-summary strong{font-size:19px}.section-head{align-items:start;flex-direction:column}.path-progress{text-align:left}.work-head h2{font-size:27px}.work-head{flex-direction:column}.model-frame{padding:12px}.dot{width:13px;height:13px}.model-group,.share-box{min-width:56px}.brand{font-size:18px}.topbar{gap:7px;padding:9px}.language-button{padding:6px 8px}}