:root{--ink:#203d42;--muted:#647e80;--teal:#246b65;--mint:#deeee5;--cream:#f5f3ec;--line:#dce3db;--orange:#bd652e;--blue:#2461a0}*{box-sizing:border-box}body{margin:0;color:var(--ink);background:var(--cream);font:16px/1.65 system-ui,-apple-system,'Noto Sans TC',sans-serif;background-image:radial-gradient(#b5c6b333 .8px,transparent .8px);background-size:18px 18px}main{width:100%;max-width:800px;margin:auto;padding:28px 24px 40px}header{display:flex;justify-content:space-between;align-items:center;gap:16px;flex-wrap:wrap}.wordmark{display:flex;align-items:center;gap:10px;letter-spacing:1.5px;font-size:12px;font-weight:800;text-decoration:none;color:var(--ink)}.brand-symbol{border:1px solid var(--teal);border-radius:10px;padding:3px 9px;font:italic 24px Georgia;color:var(--teal)}.brand-symbol span{font:17px system-ui;padding:0 2px}.tools{display:flex;gap:6px}.intro{padding:34px 0 16px}.eyebrow{font-size:12px;font-weight:800;letter-spacing:2px;color:var(--teal);margin:0 0 8px}h1{font-size:clamp(32px,6vw,48px);line-height:1.25;letter-spacing:-1px;margin:8px 0 12px}h2{font-size:23px;line-height:1.4;margin:12px 0 18px}.subtitle{color:var(--muted);margin:0;max-width:580px}.panel{background:#fffefb;border:1px solid var(--line);border-radius:20px;padding:28px;margin:18px 0;box-shadow:0 4px 0 #dce3db4d}.mode-tabs{display:flex;padding:5px;background:#edf0e8;border-radius:12px;gap:5px}.mode-tabs button{flex:1;border:0;background:transparent;color:var(--muted)}.mode-tabs button.selected{background:#fffefb;color:var(--ink);box-shadow:0 2px 5px #203d4212}.mode-tabs button:disabled{opacity:.55}button,input,select{font:inherit}button{cursor:pointer;min-height:46px;border:1px solid var(--line);padding:10px 16px;border-radius:11px;font-weight:650;line-height:1.4;transition:background .2s,transform .2s}button:hover:not(:disabled){transform:translateY(-1px);border-color:var(--teal)}button:disabled{cursor:default;opacity:.6}.primary{background:var(--teal);color:#fff;border-color:var(--teal);width:100%;box-shadow:0 3px 0 #174c47}.primary:hover:not(:disabled){background:#1a5b55}.quiet{background:#fffefb;color:var(--ink);font-size:14px}.quiet[aria-pressed=true]{background:var(--mint)}button:focus-visible,input:focus-visible,select:focus-visible,summary:focus-visible{outline:3px solid #d59343;outline-offset:3px}input,select{min-height:46px;border:1px solid #b9c9c4;border-radius:10px;padding:10px 12px;background:#fff;color:var(--ink);min-width:0}#startForm{display:flex;gap:16px;align-items:flex-end;flex-wrap:wrap}#startForm label{flex:1;min-width:180px}#startForm label span{display:block;font-size:14px;margin-bottom:5px}#startForm input{width:100%}#startForm button{width:auto;min-width:180px}.small{font-size:13px;color:var(--muted)}.statusbar{display:flex;align-items:center;gap:14px;flex-wrap:wrap;font-size:13px;color:var(--muted);margin:24px 0 14px}.statusbar #timer{margin-left:auto;font-variant-numeric:tabular-nums}.pill{padding:4px 10px;background:var(--mint);color:var(--teal);border-radius:6px;font-weight:700}.workbench{display:grid;grid-template-columns:repeat(12,minmax(0,1fr));gap:6px}.work-item{aspect-ratio:1;background:#e4e8df;border:1px solid #d0d9ce;border-radius:8px;display:flex;justify-content:center;align-items:center;font-size:11px;color:#748675}.work-item.current{outline:2px solid var(--teal);outline-offset:2px;background:#fff}.work-item.complete{background:#d2e7db;border-color:#98c6ac}.work-item.corrected{background:#eee0cd;border-color:#ccb089}.work-item svg{width:90%;height:90%}.chapter{display:flex;justify-content:space-between;gap:8px;font-size:11px;font-weight:750;letter-spacing:1px;color:var(--muted)}#levelNumber{color:var(--teal)}.equations{display:grid;gap:12px;padding:20px 18px;background:#f3f5ef;border-radius:12px}.equations>div{display:flex;align-items:center;gap:16px}.eq-label{font-size:14px;color:var(--muted)}.math{font:500 clamp(20px,4.4vw,30px)/1.6 Georgia,'Times New Roman',serif;overflow-wrap:anywhere}.var-x{color:var(--blue);font-style:italic}.var-y{color:var(--orange);font-style:italic}.known{font-size:13px;color:var(--muted)}.answer-pair{display:grid;grid-template-columns:1fr 1fr;gap:14px}.answer-pair label{display:flex;align-items:center;gap:12px;padding:12px 14px;border:1px solid var(--line);border-radius:12px;font:bold 24px Georgia}.answer-pair input{width:100%;font:22px Georgia}.feedback{border-left:3px solid var(--teal);background:#edf4ed;padding:12px 16px;font-size:15px}.feedback.wrong{border-color:#b36f35;background:#fbf0e1}.section-label{display:flex;gap:9px;align-items:center;font-size:12px;color:var(--muted);font-weight:750;letter-spacing:1px}.dot{height:7px;width:7px;background:var(--teal);border-radius:50%}#stepCount{margin-left:auto;letter-spacing:0}.scene{height:155px;position:relative;display:flex;align-items:center;justify-content:center;background:linear-gradient(transparent 87%,#e9eee4 87%,#e9eee4 89%,transparent 89%);margin:8px 0}.scene svg{height:145px;width:260px;max-width:100%;overflow:visible}.scene .part{transform-box:fill-box;transform-origin:center;opacity:.3}.scene .part.built{opacity:1}.scene .part.moving{animation:assemble 1.3s both}.scene .turn.moving{animation:turnIn 1.3s both}.scene .rise.moving{animation:riseIn 1.3s both}.scene .spread.moving{animation:spreadIn 1.3s both}.scene .pair.moving{animation:pairIn 1.3s both}.scene .trace.moving{stroke-dasharray:240;animation:traceIn 1.4s both}.scene.waiting .part{opacity:.18}.scene.waiting:after{content:'?';position:absolute;font:42px Georgia;color:#90aaa0}.math-stage{min-height:75px;padding:18px;background:#eff4ee;border:1px dashed #b3cab8;border-radius:12px;text-align:center;font:24px/1.6 Georgia,serif}.math-stage>span[data-t]{font:14px system-ui;color:var(--muted)}.math-stage.arrive{animation:arrive .9s}.tokens{display:flex;justify-content:center;align-items:center;gap:10px;margin-top:18px;flex-wrap:wrap}.source-token,.target-token{font:21px Georgia;min-width:90px;border:2px solid #71a995;background:#e7f2e8}.source-token.picked{outline:3px solid #d59343}.target-token{border-style:dashed;background:#fff6e8;border-color:#bf975c}.source-token.flying{animation:substitute 1s both}.token-arrow{color:var(--muted)}#instruction{font-weight:600;font-size:15px;margin:20px 0 12px}.options{display:grid;grid-template-columns:1fr 1fr;gap:10px}.option{background:#fff;color:var(--ink);text-align:left;font:19px/1.65 Georgia,serif;min-height:66px;padding:12px 15px;overflow-wrap:anywhere}.option .key{font:11px system-ui;color:#8c9d90;background:#f0f2eb;border-radius:4px;padding:3px 6px;margin-right:9px;display:inline-block;vertical-align:middle}.option.correct{background:#e4f0e3;border-color:var(--teal)}.option.wrong{background:#fff0e7;border-color:#a65725}.trail{padding-left:28px;color:var(--muted);font-size:13px}.trail li{padding:8px 0 8px 8px;border-bottom:1px solid #eef0e8}.trail .trail-formula{display:block;font:19px/1.6 Georgia;color:var(--ink);overflow-wrap:anywhere}.actions{display:flex;flex-wrap:wrap;gap:10px;margin-top:20px}.actions .primary{flex:1;min-width:200px}.fraction{display:inline-flex;flex-direction:column;vertical-align:middle;text-align:center;font-size:.83em;line-height:1.1;margin:0 3px;min-width:15px}.fraction .numerator{border-bottom:1px solid currentColor;padding:0 3px 2px}.fraction .denominator{padding-top:2px}.notice{color:var(--teal);font-size:14px;min-height:24px}.error{border:1px solid #d8b394;background:#fff1e5;color:#873e1c;border-radius:10px;padding:13px 17px;overflow-wrap:anywhere}.result h2{font-size:30px}.result-stat{display:inline-flex;flex-direction:column;margin:6px 28px 14px 0}.result-stat strong{font-size:34px;color:var(--teal)}.result-stat span{font-size:13px;color:var(--muted)}.save-row{border-top:1px solid var(--line);padding:15px 0;display:flex;gap:15px;justify-content:space-between;align-items:center;flex-wrap:wrap;font-size:14px}#newAttempt{margin:15px 0}details{margin-top:15px}summary{cursor:pointer;padding:8px 0}.review-item{padding:14px 0;border-bottom:1px solid var(--line)}.ranking-head{display:flex;align-items:center;justify-content:space-between;gap:12px;flex-wrap:wrap}.ranking-head h2{font-size:20px;margin:0}.ranking-head select{font-size:13px;max-width:100%}.rank-table{width:100%;border-collapse:collapse;font-size:13px}.rank-table th,.rank-table td{text-align:left;padding:12px 4px;border-bottom:1px solid var(--line);overflow-wrap:anywhere}.rank-table td:nth-child(2){max-width:140px}.rank-table th{font-size:12px;color:var(--muted)}.pagination{display:flex;justify-content:center;align-items:center;gap:15px;margin-top:16px;font-size:13px}footer{font-size:12px;color:var(--muted);text-align:center;margin-top:32px}footer a{color:var(--teal)}footer>span{display:block;margin-top:5px;font-size:10px;letter-spacing:1px}[hidden]{display:none!important}@keyframes assemble{from{transform:translateY(-48px);opacity:.15}to{transform:translateY(0);opacity:1}}@keyframes turnIn{from{transform:rotate(-140deg) scale(.6);opacity:.15}to{transform:rotate(0) scale(1);opacity:1}}@keyframes riseIn{from{transform:translateY(50px);opacity:.1}to{transform:translateY(0);opacity:1}}@keyframes spreadIn{from{transform:scaleX(.05);opacity:.1}to{transform:scaleX(1);opacity:1}}@keyframes pairIn{from{transform:translateX(-65px);opacity:.1}to{transform:translateX(0);opacity:1}}@keyframes traceIn{from{stroke-dashoffset:240;opacity:.15}to{stroke-dashoffset:0;opacity:1}}@keyframes arrive{from{transform:translateY(12px);background:#fff0ce}to{transform:translateY(0);background:#eff4ee}}@keyframes substitute{0%{transform:translate(0);opacity:1}85%{transform:translateX(100px);opacity:.3}100%{transform:translateX(0);opacity:1}}@media(max-width:540px){main{padding:18px 14px 30px}.intro{padding-top:26px}.panel{padding:20px 17px;border-radius:16px}.options{grid-template-columns:1fr}.answer-pair{gap:8px}.answer-pair label{padding:10px 8px;gap:6px;font-size:21px}.answer-pair input{font-size:19px;padding:9px 6px}.workbench{gap:4px}.work-item{border-radius:5px;font-size:9px}.statusbar{gap:9px;font-size:12px}.equations{padding:16px 11px}.equations>div{gap:9px}.math-stage{font-size:21px}.option{font-size:18px}.chapter{letter-spacing:0}#startForm button{width:100%}.rank-table th,.rank-table td{padding:10px 3px;font-size:12px}}@media(prefers-reduced-motion:reduce){*,*:before,*:after{animation:none!important;transition:none!important;scroll-behavior:auto!important}}
.answer-pair label>span{white-space:nowrap;flex-shrink:0}
/* v1.1 — direct object manipulation */
:root{--teal:#2c6cbe;--mint:#e5f1ff;--cream:#f1f6fc;--line:#dce5ef;--ink:#253d58;--muted:#71849a}body{background-image:radial-gradient(#bbd1ec55 .8px,transparent .8px)}.intro{padding:25px 0 8px}h1{font-size:clamp(30px,5vw,42px)}.mission{padding:23px}.mission h2{margin:8px 0 12px}.equations{background:#f0f5fc;padding:11px 15px;gap:5px}.math{font-size:24px}.known{margin:8px 0 16px}.mission .section-label{font-size:11px;letter-spacing:.8px}.object-lab{margin:15px 0 19px}.mini-label{display:block;font-size:10px;letter-spacing:1.3px;font-weight:800;color:#6083a8;margin-bottom:10px}.clue-relation{background:#edfaf7;border:2px dashed #8acdb9;border-radius:15px;padding:15px 16px;margin-bottom:13px}.clue-row{display:flex;justify-content:center;gap:12px;align-items:center;flex-wrap:wrap}.algebra-tile{position:relative;display:inline-flex;vertical-align:middle;align-items:center;justify-content:center;flex-direction:column;min-width:52px;height:69px;border:1px solid #9fc1e4;border-bottom:4px solid #87b0da;border-radius:11px;background:#e6f2ff;color:#235e9a;padding:5px 10px}.tile-icon{font-family:system-ui,'Apple Color Emoji','Segoe UI Emoji';font-size:28px;line-height:1.1}.tile-letter{font:bold italic 18px Georgia;line-height:1.2}.tile-sign{position:absolute;top:-9px;left:-7px;background:#fff;border:1px solid #a0bfdd;border-radius:10px;min-width:20px;height:20px;font:bold 15px/18px system-ui;color:#2b6096;text-align:center}.large-object{background:#fff0d8;border-color:#e4bd7f;border-bottom-color:#d4a756;color:#a26719}.negative{border-color:#d89eaa;border-bottom-color:#c78597;background:#fff0f3}.negative .tile-sign{border-color:#d89eaa;color:#a3455a}.big-equals{font:bold 28px Georgia;color:#7794ab;flex-shrink:0}.sealed-content{display:flex;align-items:center;justify-content:center;border-radius:12px;width:95px;height:68px;background:#e2f0eb;color:#74aa97;font:bold 34px Georgia}.relation-content{display:flex;align-items:center;justify-content:center;gap:9px;flex-wrap:wrap}.constant-chip{display:inline-flex;align-items:center;justify-content:center;background:#fff8da;border:1px solid #dfcc7c;border-bottom:3px solid #ceba65;border-radius:10px;min-width:50px;min-height:48px;padding:6px 11px;font:bold 23px Georgia;color:#8d762e}.constant-chip.negative{background:#fff0f3;color:#a3455a;border-color:#d5a0ad}.open-kit{display:block;margin:13px auto 0;background:#2ca782;color:#fff;border-color:#248e70;box-shadow:0 3px 0 #20795f;font-size:14px;min-height:44px}.object-board{background:#fff6e9;border:2px solid #edc180;border-radius:15px;padding:15px}.object-equation{display:flex;align-items:center;justify-content:center;flex-wrap:wrap;gap:12px}.board-left{display:flex;align-items:center;justify-content:center;flex-wrap:wrap;gap:14px}.pack-button{display:inline-flex;align-items:center;justify-content:center;flex-direction:column;border:2px solid #dfaa52;background:#fffaf0;box-shadow:0 4px 0 #ebd9b7;border-radius:13px;padding:12px 10px 6px;gap:8px;min-width:82px;min-height:112px}.pack-button:not(:disabled):hover{background:#ffebc8;transform:translateY(-4px) rotate(-3deg);border-color:#c08729}.pack-button:disabled{opacity:.75}.object-caption{display:block;text-align:center;font:10px/1.4 system-ui;color:#947443;flex-basis:100%;letter-spacing:.2px}.pack-button .algebra-tile{border:0;box-shadow:none;background:transparent;padding:0;min-width:43px;height:55px}.pack-button .tile-icon{font-size:33px}.bracket-pack{display:inline-flex;align-items:center;justify-content:center;flex-wrap:wrap;gap:8px;border:2px solid #e6bd78;background:#fffdf4;padding:14px 12px 7px;box-shadow:0 4px 0 #ead9bd;min-width:100px;max-width:100%}.bracket-pack .relation-content{gap:7px}.bracket-pack .algebra-tile,.expanded-group .algebra-tile{min-width:40px;height:58px;padding:4px 7px}.bracket-pack .tile-icon,.expanded-group .tile-icon{font-size:23px}.bracket-sign{font:bold 30px Georgia;color:#b6803b}.negative-pack{border-color:#cc8e9a;background:#fff3f6}.negative-pack .bracket-sign{color:#b34b67}.expanded-group{display:inline-flex;justify-content:center;flex-wrap:wrap;gap:8px;padding:12px 10px 6px;background:#e9f4e7;border:1px solid #9fc58f;border-radius:12px}.total-value{font:bold 32px Georgia;color:#b0772c;min-width:45px;text-align:center}.object-model-note{font-size:11px;line-height:1.6;color:#8491a1;margin:12px 1px 0}.collect-field{background:#fff6e9;border:1px solid #e9c59c;border-radius:14px;padding:18px 13px;display:flex;justify-content:center;flex-wrap:wrap;gap:12px}.loose-tile{padding:2px;background:transparent;border:0;min-height:70px;box-shadow:none}.loose-tile.collected{visibility:hidden;pointer-events:none}.collect-tray{border:2px solid #8ab6dd;border-radius:15px;padding:16px;background:#edf5ff;margin:15px 0;text-align:center;min-height:110px}.collected-strip{display:flex;justify-content:center;flex-wrap:wrap;gap:10px;min-height:60px;align-items:center;margin-bottom:12px}.collected-strip .algebra-tile{min-width:40px;height:54px;padding:4px 7px}.algebra-tile[data-cancelled=true]{opacity:.3;text-decoration:line-through;filter:grayscale(.6)}.algebra-tile[data-cancelled=true]:after{content:'×';position:absolute;font:45px Georgia;color:#a04f62;opacity:.8}.balance-operation{margin-top:12px;text-align:center;background:#f3f8ff;border-radius:13px;padding:16px}.balance-sides{display:flex;justify-content:space-around;align-items:center;gap:8px;margin:15px 0;font:23px Georgia}.division-board,.back-board{background:#f0f6ff;border:1px solid #c9dcf0;border-radius:15px;padding:17px;text-align:center}.sharing-total{font:bold 34px Georgia;color:#2d68a3}.share-arrow{font-size:24px;color:#7c9bb7}.trays{display:flex;flex-wrap:wrap;justify-content:center;gap:9px}.share-tray{display:flex;flex-direction:column;align-items:center;justify-content:center;gap:5px;border:2px solid #a9bcd2;border-top:0;border-radius:0 0 12px 12px;padding:8px 8px 5px;min-width:62px;background:#fff}.share-tray .algebra-tile{height:47px;min-width:36px;padding:4px}.share-tray .tile-icon{font-size:20px}.share-tray .tile-letter{font-size:14px}.tray-value{font:bold 19px Georgia;color:#9aabba}.sign-explanation{color:#a24f68;font-size:13px;background:#fff0f5;border-radius:8px;padding:10px}.object-form{display:flex;gap:12px;align-items:flex-end;flex-wrap:wrap;margin:15px 0 0}.object-form label{flex:1;text-align:left;font-size:13px;min-width:140px}.object-form input{display:block;width:100%;margin-top:5px}.object-form button{flex:1;min-width:140px;width:auto;font-size:14px}.known-value{display:flex;gap:14px;justify-content:center;align-items:center;flex-wrap:wrap;background:#fff;border:2px solid #83b3dc;width:100%;color:#2e649c}.known-value>span:last-child{flex-basis:100%;font-size:12px}.known-value strong{font:bold 30px Georgia}.back-slots{display:flex;gap:10px;justify-content:center;align-items:center;flex-wrap:wrap;margin-top:20px;font:23px Georgia}.empty-value-slot{padding:12px 24px;border:2px dashed #acc0d7;border-radius:10px;color:#7d96b4}.revealed-value{padding:10px;background:#e0f3df;border-radius:10px;font-size:23px}.solution-pair{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin:15px 0}.solution-pair>div{background:#eff7ec;border:1px solid #b6d0a6;border-radius:13px;display:flex;align-items:center;justify-content:center;flex-wrap:wrap;gap:10px;padding:15px 10px}.solution-pair strong{font:22px Georgia}.check-circuits{margin:14px 0;display:grid;gap:8px}.check-circuit{padding:12px;background:#edf0f4;border:1px solid #d6dfe9;border-radius:10px;display:flex;align-items:center;gap:13px;color:#8391a2;font-size:13px}.check-circuit>span:first-child{font-size:23px}.check-circuit.connected{background:#edf8e8;border-color:#a1c38b;color:#52853b}.object-lab button:disabled{cursor:default}.object-ghost{position:fixed;z-index:30;pointer-events:none}.trail-details{margin-top:14px;color:#7d91a8;font-size:12px}.trail-details summary{border-top:1px solid #e5edf5}.mission .math-stage{font-size:23px;padding:12px;background:#f1f7ff;min-height:60px}.mission #instruction{font-size:14px;margin:12px 0}.mission .feedback{margin-top:12px;font-size:13px}.mission .scene{margin:10px 0;height:150px}.intro .subtitle{font-size:15px}.statusbar{margin-top:18px}.work-item.current{background:#fff6df;outline-color:#d9a051}.game-container{max-width:800px}.primary{box-shadow:0 3px 0 #224d86}.primary:hover:not(:disabled){background:#245b9e}.feedback{border-left-color:#2ca782}.source-confirmation{font-size:13px}
@media(max-width:540px){.mission{padding:17px 14px}.clue-relation,.object-board{padding:14px 10px}.algebra-tile{min-width:44px;height:61px;padding:4px 7px}.tile-icon{font-size:25px}.constant-chip{min-width:43px;padding:6px 8px;font-size:21px}.clue-row{gap:10px}.board-left{gap:11px}.pack-button{min-width:72px;min-height:101px;padding:10px 8px 6px}.bracket-pack{padding:12px 9px 6px;gap:6px}.bracket-pack .relation-content{gap:6px}.object-equation{gap:10px}.total-value{font-size:28px}.object-form{gap:9px}.object-form label,.object-form button{min-width:100%;width:100%}.back-slots{font-size:20px}.solution-pair strong{font-size:20px}.object-model-note{font-size:10px}.trays{gap:6px}.share-tray{min-width:47px;padding:6px}.mini-label{font-size:9px}.mission h2{font-size:21px}.math{font-size:23px}.chapter{font-size:10px}.sign-explanation{font-size:12px}}
.constant-preserved{text-align:center;margin:10px 0 0;font-size:12px;color:#8e7b51}.constant-preserved .constant-chip{min-height:35px;min-width:42px;font-size:18px;padding:3px 8px;margin-left:8px}
.source-steps{font-size:11px;text-align:center;margin-top:9px;color:#658c7f}.source-steps summary{padding:0}.source-steps>div{font:19px/1.6 Georgia;color:#2e5c72;padding:4px}.source-steps>span{color:#9ab6a9}
.result-fly{display:flex;align-items:center;justify-content:center;gap:10px;border:1px solid #b6d0a6;background:#eff7ec;border-radius:13px;padding:12px;color:#315b36}.result-fly strong{font:22px Georgia}
.unfilled-expression{display:inline-flex;align-items:center;justify-content:center;gap:7px;flex-wrap:wrap}.unfilled-expression .empty-value-slot{padding:9px 15px}
/* v1.2 — answer only after substitution */
.answer-after-objects{font-size:14px;color:#355f8d;margin:14px 0 0}.clue-original{text-align:center;margin:8px 0}#answerForm{border-top:1px solid #d9e5f0;padding-top:16px;margin-top:16px}.back-board>.primary{margin-top:15px}