:root{--navy:#081a33;--ink:#15283b;--muted:#50647b;--green:#167846;--blue:#3c688e;--line:#d7e1e8;--paper:#f4f7fa;--mint:#eaf6ee}*{box-sizing:border-box}body{margin:0;background:var(--paper);color:var(--ink);font:18px/1.65 system-ui,-apple-system,'Segoe UI',sans-serif}button,a,input{-webkit-tap-highlight-color:transparent}button,input{font:inherit}button{cursor:pointer}a{color:var(--blue)}button:focus-visible,a:focus-visible,input:focus-visible{outline:3px solid #146ab3;outline-offset:4px}[hidden]{display:none!important}.wrap{width:min(1100px,calc(100% - 40px));margin:auto}.top{background:var(--navy);border-bottom:4px solid var(--green)}.top .wrap{display:flex;align-items:center;justify-content:space-between;min-height:70px;gap:20px}.brand{font-weight:850;font-size:22px;color:white;text-decoration:none;letter-spacing:-1px}.brand span{color:#72d29a}.back{font-size:16px;color:#e5edf4;text-decoration:none}.back:hover{text-decoration:underline}main{padding:32px 0 60px}.breadcrumb{font-size:15px;color:var(--muted);margin-bottom:20px}.breadcrumb a{text-decoration:none}.intro{margin-bottom:25px}.eyebrow{text-transform:uppercase;letter-spacing:.12em;font-size:14px;font-weight:800;color:var(--green)}h1{font-size:clamp(32px,5vw,48px);line-height:1.14;letter-spacing:-.04em;margin:8px 0 14px}h2{font-size:clamp(25px,3.5vw,33px);line-height:1.2;letter-spacing:-.025em;margin:0 0 16px}h3{font-size:22px;line-height:1.3;margin:0 0 12px}p{margin:0 0 14px}.intro p{max-width:740px;color:var(--muted)}.tabs{display:flex;border-bottom:2px solid var(--line);gap:10px;margin-bottom:30px}.tab{background:transparent;border:0;border-bottom:4px solid transparent;margin-bottom:-2px;padding:13px 25px;color:var(--muted);font-weight:800;font-size:19px}.tab[aria-selected=true]{border-color:var(--green);color:var(--green)}.tab span{font-size:14px;margin-right:8px}.lesson-section{background:#fff;border:1px solid var(--line);border-radius:16px;margin-bottom:22px;overflow:hidden}.section-inner{padding:30px;display:grid;grid-template-columns:1fr 1fr;align-items:center;gap:34px}.num{font-size:14px;color:var(--green);font-weight:800;text-transform:uppercase;letter-spacing:.08em;margin-bottom:8px}.definition{font-size:21px;line-height:1.5}.definition strong{color:var(--green)}.diagram{margin:0;background:#f4f7fa;border-radius:12px;padding:18px}.diagram svg{display:block;width:100%;height:auto}.diagram figcaption{text-align:center;font-size:16px;color:var(--muted);margin-top:9px}.symbol-list{display:flex;gap:10px;flex-wrap:wrap;margin-top:17px}.symbol-list span{background:#eef3f8;border-radius:8px;padding:6px 12px;font-size:16px}.symbol-list b{color:var(--navy);margin-right:7px;font-size:21px}.callout{padding:16px 20px;background:var(--mint);border-left:4px solid var(--green);border-radius:0 9px 9px 0;margin:22px 0}.molecule-explain{padding:30px}.compare{display:grid;grid-template-columns:1fr 1fr;gap:20px;margin:20px 0}.compare .diagram{border:1px solid var(--line)}.compare h3{font-size:20px;margin-top:12px}.remember{font-weight:700}.keyrow{display:flex;flex-wrap:wrap;gap:10px 20px;font-size:15px;color:var(--muted);margin:15px 0 0}.keyrow span{display:flex;align-items:center;gap:7px}.swatch{width:16px;height:16px;border:2px solid #456079;border-radius:50%;display:inline-block}.he{background:#ded3fa}.o{background:#dc5353}.h{background:white}.c{background:#33485d}.btn{border:1px solid var(--navy);background:var(--navy);color:#fff;border-radius:9px;padding:10px 18px;font-weight:750;text-decoration:none;display:inline-block}.btn.secondary{background:white;color:var(--ink);border-color:var(--line)}.btn:disabled{opacity:.45;cursor:default}.next{display:flex;justify-content:flex-end;margin-top:26px}.summary{background:var(--navy);color:#fff;padding:27px 30px;border-radius:14px}.summary p:last-child{margin:0}.summary strong{color:#91dfa9}.watch-intro{max-width:740px;margin-bottom:24px}.watch-intro p{color:var(--muted)}.player{border:1px solid var(--line);background:#fff;border-radius:16px;overflow:hidden}.screen{padding:26px 35px;background:#eef3f8}.scene-top{display:flex;align-items:center;justify-content:space-between;gap:15px;font-size:15px;color:var(--muted);margin-bottom:15px}.scene-top b{color:var(--green)}#watch-svg{width:100%;display:block;max-height:340px}#watch-svg .floating{animation:drift 3s ease-in-out infinite alternate;transform-box:fill-box;transform-origin:center}#watch-svg .floating:nth-child(even){animation-delay:-1.4s}@keyframes drift{from{transform:translateY(-3px)}to{transform:translateY(3px)}}.player:not(.playing) .floating{animation-play-state:paused}.narration{padding:24px 30px 12px;min-height:165px}.narration h3{font-size:25px}.narration p{font-size:20px}.transport{padding:0 30px 26px}.controls{display:flex;gap:9px;align-items:center;flex-wrap:wrap}.time{margin-left:auto;font-variant-numeric:tabular-nums;font-size:15px;color:var(--muted)}.progress-label{display:block;font-size:14px;color:var(--muted);margin:16px 0 2px}input[type=range]{width:100%;accent-color:var(--green);cursor:pointer;min-height:28px}.chapters{display:flex;flex-wrap:wrap;gap:8px;margin-top:17px}.chapter{background:white;border:1px solid var(--line);border-radius:7px;padding:7px 11px;font-size:15px;color:var(--ink)}.chapter[aria-current=true]{border-color:var(--green);background:var(--mint);color:var(--green);font-weight:750}details{margin:24px 0;background:white;border:1px solid var(--line);border-radius:12px;padding:18px 22px}summary{cursor:pointer;font-weight:750}details li{margin:12px 0}footer{border-top:1px solid var(--line);padding:22px 0;color:var(--muted);font-size:14px}footer .wrap{display:flex;justify-content:space-between;gap:20px}footer a{color:var(--muted)}
@media(max-width:720px){body{font-size:18px}.wrap{width:calc(100% - 28px)}.top .wrap{flex-wrap:wrap;gap:0;padding:10px 0}.brand{font-size:20px}.back{font-size:14px}.section-inner,.compare{grid-template-columns:1fr;gap:18px}.section-inner,.molecule-explain{padding:22px}.tab{padding:11px 20px}.screen{padding:20px 12px}.narration{padding:20px 20px 10px;min-height:205px}.transport{padding:0 20px 22px}.controls .btn{padding:9px 12px;font-size:16px}.time{width:100%;margin-left:0}.summary{padding:23px}.next .btn{width:100%;text-align:center}footer .wrap{flex-direction:column;gap:6px}}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important}#watch-svg .floating{animation:none}}
@media print{.top,.tabs,.next,footer,#watch{display:none!important}#learn{display:block!important}.lesson-section{break-inside:avoid}.wrap{width:100%}body{font-size:12pt}.section-inner{padding:16px}main{padding:0}}

.game-head{display:flex;align-items:center;justify-content:space-between;gap:16px;margin-bottom:18px}.game-head h2{margin:0}.score-chip{background:var(--navy);color:white;border-radius:30px;padding:9px 17px;font-weight:800;white-space:nowrap;font-size:16px}.round-track{display:flex;gap:7px;margin:16px 0 22px}.round-track span{height:8px;flex:1;background:#dbe4ed;border-radius:10px}.round-track .done{background:var(--green)}.round-track .current{background:var(--blue)}.game-layout{display:grid;grid-template-columns:1.05fr 1fr;gap:0;border:1px solid var(--line);border-radius:18px;overflow:hidden;background:white}.sample-board{padding:23px;background:#edf3f8;display:flex;flex-direction:column;justify-content:center;min-width:0}.board-label{display:flex;justify-content:space-between;gap:10px;font-size:15px;font-weight:750;color:var(--muted)}#sample{width:100%;height:auto;display:block;margin:12px 0;aspect-ratio:400/270}.board-note{font-size:14px;color:var(--muted);margin:0}.question-side{padding:28px;min-width:0}.step-label{font-size:14px;color:var(--green);font-weight:850;text-transform:uppercase;letter-spacing:.08em;margin-bottom:8px}#game-question{font-size:25px;line-height:1.25}.choice-list{display:grid;gap:10px}.choice{display:flex;justify-content:space-between;align-items:center;gap:10px;background:white;border:2px solid #cbd8e4;padding:13px 16px;border-radius:11px;font-size:19px;text-align:left;color:var(--ink);font-weight:750;min-height:58px}.choice:hover:not(:disabled){border-color:var(--blue);background:#f0f6fc}.choice:disabled{cursor:default}.choice.correct{border-color:var(--green);background:#eaf7ee;color:#12663d}.choice.wrong{border-color:#a95312;background:#fff3e6;color:#80410e}.feedback-box{padding:15px 17px;border-radius:10px;margin-top:18px;background:#edf7f0;color:#155b38;line-height:1.5}.feedback-box.retry{background:#fff5e9;color:#80410e}.feedback-box strong{display:block;font-size:19px;margin-bottom:5px}.feedback-box p{margin:0;font-size:17px}.hint{margin-top:16px;font-size:16px;color:var(--muted)}.hint summary{font-size:16px}.hint p{margin-top:10px}.game-next{margin-top:16px;width:100%}.results{background:white;border:1px solid var(--line);border-radius:18px;padding:38px;text-align:center}.result-star{font-size:48px;color:var(--green);line-height:1;margin-bottom:20px}.result-score{font-size:48px;font-weight:900;color:var(--green);margin:12px 0}.results p{max-width:550px;margin:12px auto 24px}.game-return{margin:20px 0;color:var(--muted);font-size:15px}.confetti-free{animation:pop .25s ease-out}@keyframes pop{from{transform:scale(.97)}to{transform:scale(1)}}
@media(max-width:720px){.game-layout{grid-template-columns:1fr}.sample-board{padding:17px}#sample{max-height:215px;margin:5px 0}.question-side{padding:22px}.game-head{align-items:flex-start}.game-head h2{font-size:27px}.score-chip{font-size:14px;padding:8px 12px}.results{padding:27px}.choice{min-height:54px}.game-head{gap:8px}}
@media(prefers-reduced-motion:reduce){.confetti-free{animation:none}}

.clue-button{border:0;background:transparent;color:var(--blue);text-decoration:underline;font:inherit;font-size:16px;min-height:44px;padding:8px 0;cursor:pointer}
@media(max-width:720px){
body.game-mode .top,body.game-mode .breadcrumb,body.game-mode .intro,body.game-mode footer{display:none}
body.game-mode main{padding:6px 0 max(6px,env(safe-area-inset-bottom));width:calc(100% - 20px)}
body.game-mode .tabs{margin-bottom:8px;gap:8px}body.game-mode .tab{padding:7px 16px;min-height:44px;font-size:18px}
body.game-mode .game-head{margin-bottom:4px;align-items:center}body.game-mode .game-head .eyebrow,body.game-mode .game-intro,body.game-mode .game-return{display:none}
body.game-mode .game-head h2{font-size:23px}body.game-mode .score-chip{padding:4px 12px;font-size:15px}
body.game-mode .round-track{margin:5px 0 7px;gap:5px}body.game-mode .round-track span{height:5px}
body.game-mode .game-layout{border-radius:12px;gap:0}body.game-mode .sample-board{padding:8px 12px 2px}
body.game-mode .board-label{font-size:14px;line-height:20px}body.game-mode .board-note{display:none}
body.game-mode #sample{height:clamp(80px,calc(100dvh - 490px),210px);max-height:none;aspect-ratio:auto;margin:0}
body.game-mode .question-side{padding:10px 12px;display:grid;grid-template-columns:1fr 1fr;gap:6px}
body.game-mode .step-label{font-size:14px;line-height:18px;margin:0;grid-column:1/-1}
body.game-mode #game-question{font-size:20px;line-height:1.2;margin:0 0 2px;grid-column:1/-1}
body.game-mode .choice-list{grid-column:1/-1;grid-template-columns:repeat(3,minmax(0,1fr));gap:6px}
body.game-mode .choice{display:block;min-height:52px;padding:5px 4px;font-size:16px;line-height:1.15;text-align:center;border-radius:8px;overflow-wrap:normal}
body.game-mode #game-feedback{grid-column:1/-1;min-height:100px;display:flex;align-items:center}
body.game-mode .feedback-box{width:100%;padding:8px 10px;margin:0;line-height:1.25}
body.game-mode .feedback-box strong{font-size:16px;margin-bottom:3px}body.game-mode .feedback-box p{font-size:16px;line-height:1.25}
body.game-mode .clue-button{margin:0;min-height:44px;padding:6px 0;grid-column:1/-1;text-align:center}
body.game-mode .game-next{grid-column:1/-1;min-height:44px;margin:0;padding:7px 12px;font-size:16px}
body.game-mode #go-learn{font-size:15px;min-height:44px;margin-top:5px;padding:7px 12px}
body.game-mode .results{padding:20px}body.game-mode .result-star{font-size:30px;margin-bottom:10px}body.game-mode .results h2{font-size:26px}body.game-mode .results p{font-size:16px}
}
@media(max-width:720px) and (max-height:590px) and (orientation:landscape){
body.game-mode .game-layout{grid-template-columns:.8fr 1fr}body.game-mode #sample{height:180px}body.game-mode .question-side{padding:8px}body.game-mode #game-feedback{min-height:70px}body.game-mode .game-head{display:none}body.game-mode .round-track{margin:2px 0 5px}
}

.formula-note{padding:16px 20px;background:#edf3f8;border-left:4px solid var(--blue);font-size:24px;font-weight:750;border-radius:8px;margin:16px 0}.formula-note span{display:block;font-size:17px;font-weight:400;margin-top:7px}.formula-note.balanced{background:var(--mint);border-color:var(--green)}
#sample.formula-sample{display:flex;flex-direction:column;align-items:center;justify-content:center;gap:5px;min-height:230px}#sample svg{width:100%;max-height:170px;min-height:0;flex:1}.quiz-formula{font-size:30px;line-height:1.3;font-weight:800;text-align:center;white-space:nowrap}.formula-caption{font-size:16px;text-align:center;color:var(--muted)}.blank{color:var(--green);border-bottom:3px solid var(--green)}.word-reaction{font-size:24px;font-weight:750;line-height:1.4;text-align:center;display:grid;gap:5px}.word-reaction b{font-size:32px;color:var(--green)}
@media(max-width:720px){body.game-mode #sample.formula-sample{min-height:0}body.game-mode .quiz-formula{font-size:24px}body.game-mode #sample svg{max-height:140px}body.game-mode .word-reaction{font-size:21px;gap:0;line-height:1.2}body.game-mode .word-reaction b{font-size:23px}body.game-mode .formula-caption{font-size:14px}.formula-note{font-size:21px;padding:13px}.formula-note span{font-size:16px}}

.word-reaction{display:flex!important;flex-direction:row;flex-wrap:nowrap;align-items:center;justify-content:center;gap:9px;font-size:24px;white-space:nowrap;width:100%}.word-reaction span{font:inherit;margin:0}.word-reaction b{font:inherit;color:var(--green)}
@media(max-width:720px){.word-reaction,body.game-mode .word-reaction{display:flex;flex-direction:row;gap:5px;font-size:clamp(16px,4.4vw,22px);line-height:1.3}.word-reaction b,body.game-mode .word-reaction b{font-size:inherit}.formula-note:has(.word-reaction){padding:12px 4px}.quiz-formula{max-width:100%}}