@charset "UTF-8";
:root{--ink:#243d35;--green:#205d49;--green-dark:#173f33;--green-soft:#edf3ed;--muted:#839087;--line:#e4e8df;--paper:#f7f8f2;--orange:#d89145;--violet:#9670ac;--radius:16px;font-family:"Segoe UI","Microsoft YaHei","PingFang SC",sans-serif;color:var(--ink);background:var(--paper);font-synthesis:none}
*{box-sizing:border-box}body{margin:0;display:flex;min-height:100vh}button,a,input{ -webkit-tap-highlight-color:transparent}button,input{font:inherit}button{cursor:pointer}button{transition:background .18s,box-shadow .18s,transform .18s}button:disabled{cursor:default;opacity:.4}button:focus-visible,a:focus-visible,summary:focus-visible{outline:3px solid #dfa550;outline-offset:3px}button:hover:not(:disabled){filter:brightness(.97)}button:active:not(:disabled){transform:translateY(1px)}button svg,[data-icon] svg{width:18px;height:18px;display:block;fill:none;stroke:currentColor;stroke-width:1.65;stroke-linecap:round;stroke-linejoin:round}a{color:inherit;text-decoration:none}.sidebar{width:226px;flex-shrink:0;border-right:1px solid var(--line);padding:34px 20px 20px;display:flex;flex-direction:column;background:#f2f4ec;position:fixed;inset:0 auto 0 0}.brand{display:flex;align-items:center;gap:12px;padding-left:7px;font-size:23px;font-weight:650;letter-spacing:2px}.brand small{display:block;font-size:9px;letter-spacing:2.8px;font-weight:600;margin-top:5px;color:#7b8b7d}.brand-mark{width:43px;height:48px;display:grid;place-items:center;background:var(--green-dark);border-radius:12px;color:#f9f8e9}.brand-mark svg{width:32px;fill:none;stroke:currentColor;stroke-width:1.3}.sidebar-caption{font-size:11px;letter-spacing:1.1px;color:#8a9386;margin:41px 0 18px 12px}nav{display:flex;flex-direction:column;gap:8px}.nav-item{display:flex;align-items:center;gap:12px;text-align:left;border:1px solid transparent;padding:16px 12px;border-radius:11px;background:transparent;color:#7d887b;width:100%}.nav-item .nav-number{font-size:11px;font-weight:500;opacity:.7;font-variant-numeric:tabular-nums;align-self:flex-start;padding-top:3px}.nav-item strong{font-size:14px;display:block;font-weight:550;letter-spacing:.5px}.nav-item small{display:block;font-size:10px;margin-top:5px;opacity:.7}.nav-item.active{background:var(--green-dark);color:#fff;box-shadow:0 5px 10px #183e340d}.nav-item.active .nav-number{color:#bdd3a9}.nav-item:not(.active):hover{background:#e7ece0}.nav-arrow{margin-left:auto;font-size:17px}.sidebar-note{margin:auto 12px 30px;padding-top:42px;color:#788c76}.tiny-spark{font-size:28px;color:#b4bea1}.sidebar-note p{font-family:"Microsoft YaHei",sans-serif;font-size:13px;line-height:1.9;letter-spacing:1.5px;margin:10px 0}.sidebar-note svg{width:145px;height:85px;stroke:#a7b393;stroke-width:1.4;fill:none}.sidebar-note .sketch{stroke:#c6cfb4;stroke-dasharray:3 4}.sidebar-bottom{font-size:10px;color:#8c9788;display:flex;align-items:center;gap:7px;padding-top:17px;border-top:1px solid #dde3d4;white-space:nowrap}.status-dot{width:6px;height:6px;border-radius:100%;background:#739267;display:inline-block;flex-shrink:0}.sidebar-bottom-right{margin-left:auto}main{margin-left:226px;min-width:0;flex:1}.topbar{height:83px;display:flex;align-items:center;justify-content:space-between;padding:0 38px;border-bottom:1px solid var(--line);background:#fafbf6}.breadcrumb{display:flex;align-items:center;gap:16px;font-size:12px;color:#8a9388}.breadcrumb span:last-child{color:#4f6656}.breadcrumb span:first-child{color:#c0c8b9}.top-actions{display:flex;align-items:center;gap:18px}.quiet-button,.outline-button{display:flex;align-items:center;justify-content:center;gap:7px;padding:9px 12px;font-size:12px;color:#63735f;background:none;border:0;border-radius:7px}.outline-button{border:1px solid #d6dfcc;color:#3c5e45;background:#fafbf6}.lesson{padding:31px 38px 0;max-width:1780px;margin:auto}.lesson-heading{display:flex;align-items:center;justify-content:space-between;margin-bottom:26px}.eyebrow{font-size:10px;letter-spacing:1.9px;font-weight:650;color:#839177}h1{font-size:29px;letter-spacing:1px;line-height:1.4;font-weight:600;margin:9px 0 8px}.lesson-heading p{font-size:12px;color:#899083;margin:0;line-height:1.6}.lesson-tag{display:flex;align-items:center;gap:7px;font-size:11px;border:1px solid #dfe5d6;padding:8px 12px;border-radius:30px;color:#748166;white-space:nowrap;margin-left:15px}.workspace{display:grid;grid-template-columns:minmax(0,1fr) 272px;gap:21px;align-items:start}.board-card{min-width:0;border:1px solid #dfe5d9;border-radius:var(--radius);background:#fefef9;overflow:hidden;box-shadow:0 4px 18px #2c3a211f}.board-toolbar{height:56px;display:flex;align-items:center;justify-content:space-between;padding:0 22px;border-bottom:1px solid #e9ecdf;background:#fffffb}.board-label{display:flex;align-items:center;gap:9px;font-size:12px;font-weight:600}.board-label [data-icon]{color:#738269}.board-tools{display:flex;align-items:center;gap:7px}.tool-button{display:flex;gap:5px;align-items:center;font-size:11px;border:0;padding:7px 9px;border-radius:6px;color:#89927f;background:transparent}.tool-button svg{width:15px;height:15px}.tool-button.active{background:#edf1e5;color:#5a7351}.toolbar-divider{width:1px;height:16px;background:#e5e9dc;margin:0 3px}.canvas-wrap{position:relative;width:100%;aspect-ratio:960 / 640;min-height:340px;background:#fcfdf7;display:flex;align-items:center;justify-content:center}#board{width:100%;height:100%;position:absolute;inset:0;touch-action:none;user-select:none;-webkit-user-select:none}#board text{font-family:"Segoe UI","Microsoft YaHei",sans-serif}#board .math-label{font-family:Georgia,"Times New Roman",serif;font-style:italic}#board .board-text{fill:#87927e;font-size:15px}#board [data-drag]{cursor:grab}#board [data-drag]:active{cursor:grabbing}#board [data-drag]:focus{outline:none}#board [data-drag]:focus-visible circle{stroke:#e0a44f;stroke-width:5}.board-corner{position:absolute;left:23px;bottom:18px;font-size:10px;color:#929c86;pointer-events:none}.board-footer{min-height:56px;display:flex;align-items:center;justify-content:space-between;gap:10px;padding:12px 21px;border-top:1px solid #e9ecdf;background:#fffffc;font-size:11px;color:#7c8b71;line-height:1.6}.board-footer .hint{display:flex;align-items:center;gap:7px}.board-footer svg{width:15px;height:15px;flex-shrink:0}.board-footer .legend{display:flex;gap:12px;white-space:nowrap}.legend i{display:inline-block;width:6px;height:6px;border-radius:50%;margin-right:5px}.control-panel{display:flex;flex-direction:column;gap:15px;min-width:0}.panel-card{border:1px solid #e1e6d9;border-radius:var(--radius);background:#fffffb;padding:21px}.panel-card h2{font-size:14px;letter-spacing:.4px;margin:0 0 16px;font-weight:600;display:flex;align-items:center;justify-content:space-between}.panel-card h2 .mini-label{font-size:9px;color:#93a087;letter-spacing:1.1px;font-weight:500}.panel-intro{font-size:11px;color:#86927c;line-height:1.85;margin:0 0 16px}.instruction-row{display:flex;gap:10px;margin:14px 0}.instruction-index{font-size:10px;width:21px;height:21px;display:grid;place-items:center;background:#eef2e6;border-radius:50%;color:#7a8d66;flex-shrink:0}.instruction-row strong{display:block;font-size:12px;font-weight:500;line-height:1.7;color:#516747}.instruction-row p{font-size:10px;line-height:1.7;color:#929984;margin:3px 0 0}.primary-button,.secondary-button{width:100%;display:flex;align-items:center;justify-content:center;gap:7px;border-radius:8px;padding:11px 9px;font-size:12px;letter-spacing:.4px;border:1px solid var(--green);background:var(--green);color:white}.secondary-button{background:#fffffb;border-color:#dce3d2;color:#6b7e5c}.primary-button svg,.secondary-button svg{width:15px;height:15px}.button-row{display:flex;gap:8px;margin-top:9px}.button-row button{flex:1;font-size:11px;padding:9px 7px}.panel-separator{height:1px;background:#edf0e5;margin:17px 0}.range-label{display:flex;align-items:center;justify-content:space-between;margin:14px 0 7px;font-size:11px;color:#829174}.range-label output{font-weight:600;color:#4d6a46;font-variant-numeric:tabular-nums}input[type=range]{width:100%;height:16px;accent-color:var(--green);cursor:pointer;margin:0}input[type=range]:focus-visible{outline:2px solid #dfa550;outline-offset:3px}.toggle-row{display:flex;align-items:center;justify-content:space-between;gap:10px;font-size:11px;color:#7c8a6f;margin:15px 0 0}.toggle-row input{appearance:none;width:30px;height:17px;border-radius:20px;background:#d9dfd0;position:relative;margin:0;cursor:pointer;flex-shrink:0;transition:background .2s}.toggle-row input:before{content:"";width:11px;height:11px;background:white;position:absolute;top:3px;left:3px;border-radius:50%;transition:transform .2s}.toggle-row input:checked{background:#547859}.toggle-row input:checked:before{transform:translateX(13px)}.toggle-row input:focus-visible{outline:2px solid #dfa550;outline-offset:3px}.question-card{background:#eff2e7;border:1px solid #e2e8d7;border-radius:var(--radius);padding:20px}.question-card .question-label{display:flex;gap:7px;align-items:center;color:#879575;font-size:10px;letter-spacing:1px}.question-card h3{font-size:13px;font-weight:500;line-height:1.9;margin:11px 0 7px;color:#536a45}.question-card p{font-size:10px;line-height:1.8;color:#8a977c;margin:0}.measurement-status{border-radius:8px;background:#f4f5ed;padding:11px 12px;margin-top:14px;color:#7b866e;font-size:11px;line-height:1.8}.measurement-status.success{background:#eaf4e9;color:#377047}.measurement-status.warn{background:#fff3df;color:#a17b38}.metric-row{display:flex;align-items:center;justify-content:space-between;padding:11px 0;border-bottom:1px solid #edf0e7;font-size:11px;color:#829074}.metric-row:last-child{border-bottom:0}.metric-row strong{font-size:21px;font-family:Georgia,"Times New Roman",serif;font-weight:400;color:var(--green);font-variant-numeric:tabular-nums}.metric-row strong small{font-family:"Segoe UI",sans-serif;font-size:10px;margin-left:4px;color:#839173}.formula{font-size:13px;color:#416539;line-height:2;text-align:center;padding:11px;background:#edf3e5;border-radius:8px;margin-top:12px}.step-list{display:flex;gap:6px;margin-bottom:16px}.step-dot{width:100%;height:5px;border:none;padding:0;border-radius:20px;background:#e8eddf}.step-dot.active{background:#63835b}.step-description{min-height:51px;font-size:11px;color:#879478;line-height:1.9;margin:8px 0 13px}.step-title{font-size:14px;margin:0;color:#48653c;font-weight:550}.lesson-footer{display:flex;justify-content:space-between;align-items:center;color:#96a08c;font-size:10px;padding:24px 2px}.lesson-footer>span{display:flex;align-items:center;gap:6px;letter-spacing:.6px}.footer-dot{height:4px;width:4px;background:#a9b695;display:inline-block;border-radius:50%}.lesson-footer>div{display:flex;gap:25px;align-items:center}.lesson-footer #scene-count{font-size:10px;color:#a3ae96;font-variant-numeric:tabular-nums;letter-spacing:2px}.next-scene{border:0;background:none;color:#687f59;font-size:11px;display:flex;gap:15px;align-items:center;padding:5px 0}.trace-note{font-size:10px;line-height:1.85;color:#8b987e;margin:13px 0 0}.disclosure{font-size:11px;color:#7f906f;line-height:1.8;margin-top:14px}.disclosure summary{cursor:pointer}.disclosure p{font-size:10px;margin:9px 0 0}.speed-options{display:flex;gap:5px;margin-top:9px}.speed-options button{border:1px solid #dfe5d7;border-radius:6px;background:#fffffb;color:#849374;padding:6px 0;flex:1;font-size:10px}.speed-options button.active{background:#eef3e5;color:#406039;border-color:#b8cbaa}.toast{position:fixed;bottom:26px;left:calc(50% + 113px);transform:translate(-50%,20px);opacity:0;transition:.25s;pointer-events:none;z-index:20;background:#254c3e;color:#fafcf6;padding:12px 20px;border-radius:10px;box-shadow:0 5px 25px #1d372b22;font-size:12px;max-width:85vw}.toast.visible{opacity:1;transform:translate(-50%,0)}dialog{border:1px solid #e0e5d9;border-radius:20px;padding:34px;width:540px;max-width:92vw;color:var(--ink);background:#fdfef8;box-shadow:0 20px 80px #102c2c33}dialog::backdrop{background:#16362a55;backdrop-filter:blur(4px)}dialog h2{font-size:23px;margin:12px 0}dialog p,dialog li{font-size:12px;line-height:1.9;color:#77846c}dialog ul{padding-left:18px}dialog li{margin:10px 0}.dialog-close{position:absolute;right:20px;top:16px;background:none;border:0;font-size:27px;color:#819476}.help-shortcuts{background:#eff3e7;border-radius:8px;padding:10px}kbd{background:white;border:1px solid #dce4d1;border-radius:4px;padding:1px 5px;font-size:10px}.help-fine{font-size:10px!important;color:#9aa38e!important}.trail-path{fill:none;stroke-linecap:round;stroke-linejoin:round}.svg-chip{fill:#fffffa;stroke:#e2e9d8}.ruler-body{fill:#f5e2a5;fill-opacity:.64;stroke:#cfb875;stroke-width:1.3}.dimension-label{paint-order:stroke;stroke:#fcfdf7;stroke-width:8px;stroke-linejoin:round;fill:#557a55;font-size:19px}.draggable-glow{fill:#e6c878;opacity:.16}
@media(min-width:1600px){.workspace{grid-template-columns:minmax(0,1fr) 294px}.panel-card{padding:25px}.canvas-wrap{max-height:calc(100vh - 350px);min-height:480px}.lesson{padding-top:38px}.lesson-heading{margin-bottom:32px}.panel-intro,.instruction-row p,.question-card p{font-size:12px}.instruction-row strong,.range-label,.toggle-row{font-size:13px}.board-footer{font-size:12px}}
@media(max-width:1200px){.sidebar{width:193px;padding:28px 14px 16px}.brand{font-size:20px;gap:8px}.brand-mark{width:38px;height:43px}.brand small{font-size:8px;letter-spacing:2px}.nav-item{padding:15px 9px;gap:9px}.nav-item strong{font-size:13px}main{margin-left:193px}.lesson{padding:25px 25px 0}.topbar{padding:0 25px}.workspace{grid-template-columns:minmax(0,1fr) 245px;gap:16px}.panel-card{padding:17px}.question-card{padding:17px}.canvas-wrap{min-height:365px}.toast{left:calc(50% + 96px)}h1{font-size:26px}.board-footer .legend{gap:7px;font-size:10px}.board-footer{padding:12px}.board-toolbar{padding:0 14px}}
@media(max-width:980px){.sidebar{width:164px;padding:25px 10px 16px}.brand{font-size:17px;gap:6px;padding-left:3px}.brand-mark{width:32px;height:37px}.brand small{font-size:6px;letter-spacing:1.9px}.sidebar-caption{font-size:9px;margin-left:5px}.nav-item{gap:6px;padding:14px 8px}.nav-item strong{font-size:12px}.nav-item small{font-size:8px}.nav-arrow{display:none}.sidebar-bottom{font-size:8px;gap:4px}main{margin-left:164px}.lesson{padding:24px 20px 0}.workspace{grid-template-columns:minmax(0,1fr)}.control-panel{display:grid;grid-template-columns:1fr 1fr;gap:14px}.control-panel>.panel-card:first-child{grid-row:span 2}.canvas-wrap{aspect-ratio:960/600;min-height:340px;max-height:540px}.topbar{height:72px;padding:0 20px}.lesson-tag{display:none}.sidebar-note{margin-left:5px;margin-right:5px}.sidebar-note svg{width:130px}.toast{left:calc(50% + 82px)}}
@media(max-width:680px){body{display:block}.sidebar{position:relative;width:auto;padding:18px 15px 12px;border-right:0;border-bottom:1px solid var(--line)}.brand{font-size:20px}.brand small{font-size:8px}.brand-mark{width:36px;height:39px}.sidebar-caption,.sidebar-note,.sidebar-bottom{display:none}nav{flex-direction:row;gap:6px;margin-top:17px;overflow-x:auto;padding-bottom:3px}.nav-item{flex:0 0 auto;width:auto;padding:10px 12px;gap:6px;border-radius:8px}.nav-item .nav-number{font-size:9px;padding-top:2px}.nav-item strong{font-size:11px}.nav-item small{display:none}main{margin-left:0}.topbar{height:54px;padding:0 17px}.breadcrumb{font-size:10px;gap:7px}.top-actions{gap:4px}.quiet-button{padding:7px}.quiet-button>span:last-child{display:none}.outline-button{padding:6px 8px;font-size:10px}.lesson{padding:24px 14px 0}.lesson-heading{margin-bottom:20px}.eyebrow{font-size:9px}h1{font-size:23px}.lesson-heading p{font-size:10px}.workspace{gap:14px}.canvas-wrap{aspect-ratio:1.36;min-height:280px}.board-toolbar{height:46px}.board-footer{font-size:9px}.board-footer .legend{display:none}.board-corner{font-size:8px;left:15px;bottom:10px}.control-panel{grid-template-columns:1fr 1fr;gap:10px}.panel-card,.question-card{padding:15px}.panel-card h2{font-size:12px}.panel-card h2 .mini-label{display:none}.question-card h3{font-size:11px}.panel-intro{font-size:10px}.instruction-row{gap:7px}.instruction-row strong{font-size:11px}.instruction-row p{font-size:9px}.range-label,.toggle-row{font-size:10px}.button-row{gap:5px}.button-row button{font-size:9px}.primary-button,.secondary-button{font-size:11px}.metric-row strong{font-size:18px}.formula{font-size:11px}.lesson-footer{font-size:9px;padding:19px 2px}.lesson-footer>div{gap:12px}.toast{left:50%;white-space:normal;width:max-content}.step-description{font-size:10px}.step-title{font-size:12px}.help-shortcuts{font-size:10px!important}.breadcrumb>span:last-child{max-width:80px;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}}
.ui-icon{width:18px;height:18px;display:block;fill:none;stroke:currentColor;stroke-width:1.65;stroke-linecap:round;stroke-linejoin:round;flex-shrink:0}.question-label .ui-icon{width:15px;height:15px}
@media(min-width:981px){.canvas-wrap{max-height:calc(100dvh - 415px);min-height:340px}.control-panel{max-height:calc(100dvh - 300px);overflow-y:auto;scrollbar-width:thin;scrollbar-color:#d6dfcc transparent;padding-right:2px}}
@media(min-width:981px) and (max-height:820px){.topbar{height:65px}.lesson{padding-top:22px}.lesson-heading{margin-bottom:18px}h1{font-size:26px}.canvas-wrap{max-height:calc(100dvh - 374px);min-height:300px}.control-panel{max-height:calc(100dvh - 265px)}.panel-card{padding:17px}.instruction-row{margin:10px 0}.panel-card h2{margin-bottom:13px}.lesson-footer{padding-top:18px;padding-bottom:18px}}
@media(max-width:380px){.control-panel{grid-template-columns:1fr}.control-panel>.panel-card:first-child{grid-row:auto}}
@media(prefers-reduced-motion:reduce){*{transition:none!important}}

/* Classroom typography: readable explanations with a clear title hierarchy. */
h1{font-size:34px;line-height:1.4}
.lesson-heading p{font-size:20px;line-height:1.65;color:#4f6656}
.eyebrow{font-size:13px;letter-spacing:1px;color:#65765d}
.lesson-tag{font-size:14px;color:#526b47}
.breadcrumb{font-size:14px;color:#60715c;min-width:0}
.quiet-button,.outline-button{font-size:14px}
.brand small{font-size:12px;letter-spacing:1.5px}
.sidebar{overflow-y:auto;scrollbar-width:thin}
.sidebar-caption{font-size:13px;letter-spacing:0;color:#63745b;margin-top:28px}
.nav-item{padding-top:12px;padding-bottom:12px}
.nav-item strong{font-size:19px}
.nav-item small{font-size:12px;line-height:1.6;opacity:.9}
.nav-item .nav-number{font-size:13px}
.sidebar-note p{font-size:15px}
.sidebar-bottom{font-size:12px;color:#63745b}
.board-label{font-size:16px}
.tool-button{font-size:14px;color:#5a704e}
.board-corner{font-size:14px;color:#576d4c;background:#fcfdf7e8;padding:3px 6px;border-radius:4px}
.board-footer{font-size:14px;color:#536b47;flex-wrap:wrap;row-gap:6px}
.board-footer .legend{font-size:13px;flex-wrap:wrap}
.panel-card h2{font-size:19px;line-height:1.5;flex-wrap:wrap;gap:4px 8px}
.panel-card h2 .mini-label{font-size:12px;color:#647a54;letter-spacing:.5px}
.panel-intro,.step-description{font-size:16px;line-height:1.8;color:#52694a}
.instruction-row strong{font-size:17px;color:#385934}
.instruction-row p{font-size:15px;line-height:1.75;color:#5f7254}
.instruction-index{font-size:14px;width:25px;height:25px}
.primary-button,.secondary-button{font-size:16px;min-height:44px}
.button-row button{font-size:14px;min-width:0}
.range-label,.toggle-row,.metric-row{font-size:15px;line-height:1.6;color:#556d48}
.range-label output{white-space:nowrap;margin-left:8px}
.measurement-status{font-size:15px;color:#556b47}
.question-card .question-label{font-size:14px;letter-spacing:.5px;color:#61764f}
.question-card h3{font-size:18px;line-height:1.7;color:#3e5e32}
.question-card p{font-size:16px;line-height:1.8;color:#5b704b}
.metric-row strong{font-size:27px}
.metric-row strong small{font-size:14px;color:#5b714b}
.formula{font-size:17px;line-height:1.85}
.step-title{font-size:19px;line-height:1.6}
.trace-note,.disclosure,.disclosure p{font-size:14px;line-height:1.8;color:#5c714d}
.speed-options button{font-size:14px;padding:8px 2px;color:#546e45}
.lesson-footer{font-size:12px;color:#637852;gap:16px}
.lesson-footer #scene-count{font-size:12px;color:#637852;white-space:nowrap}
.next-scene{font-size:14px;white-space:nowrap}
.toast{font-size:16px}
dialog{width:650px;max-height:90dvh;overflow-y:auto}
dialog h2{font-size:28px}
dialog p,dialog li{font-size:17px;line-height:1.8;color:#52694a}
.help-fine{font-size:14px!important;color:#5c714d!important}
.help-shortcuts{font-size:15px!important}
kbd{font-size:13px}
.dimension-label{font-size:24px}

@media(min-width:981px){
  .lesson{height:calc(100dvh - 83px);min-height:660px;display:flex;flex-direction:column}
  .lesson-heading,.lesson-footer{flex-shrink:0}
  .lesson-heading{align-items:flex-start}
  .lesson-tag{margin-top:28px}
  .workspace{grid-template-columns:minmax(0,1fr) 310px;flex:1;min-height:360px;align-items:stretch}
  .board-card{display:flex;flex-direction:column;min-height:0}
  .board-toolbar,.board-footer{flex-shrink:0}
  .canvas-wrap{flex:1;aspect-ratio:auto;min-height:240px;max-height:none}
  .control-panel{height:100%;max-height:100%;min-height:0}
  .panel-card{padding:20px;flex-shrink:0}
  .question-card{flex-shrink:0}
}
@media(min-width:1600px){
  .workspace{grid-template-columns:minmax(0,1fr) 340px}
  h1{font-size:38px}
  .lesson-heading p{font-size:22px}
}
@media(min-width:981px) and (max-width:1200px){
  .workspace{grid-template-columns:minmax(0,1fr) 280px}
  .panel-card{padding:17px}
  h1{font-size:32px}
}
@media(min-width:981px) and (max-height:820px){
  .lesson{height:calc(100dvh - 65px);min-height:635px}
  .sidebar-note{display:none}
  .sidebar-bottom{margin-top:auto}
}
@media(min-width:681px) and (max-width:980px){
  h1{font-size:30px}
  .lesson-heading p{font-size:19px}
  .sidebar-caption{font-size:12px}
  .sidebar-bottom{font-size:10px}
  .nav-item{padding-left:6px;padding-right:6px;gap:6px}
  .nav-item strong{font-size:18px}
  .nav-item small{font-size:11px}
}
@media(max-width:680px){
  h1{font-size:27px}
  .lesson-heading p{font-size:18px;line-height:1.65}
  .eyebrow{font-size:12px;letter-spacing:.5px}
  .brand small{font-size:11px}
  .nav-item strong{font-size:16px}
  .nav-item .nav-number{font-size:12px}
  .topbar{height:auto;min-height:60px;gap:8px;padding:10px 14px}
  .breadcrumb{font-size:12px;gap:5px;flex-wrap:wrap}
  .top-actions{flex-shrink:0}
  .outline-button{font-size:12px}
  .control-panel{grid-template-columns:1fr}
  .control-panel>.panel-card:first-child{grid-row:auto}
  .panel-card,.question-card{padding:20px}
  .panel-card h2 .mini-label{display:inline}
  .board-label{font-size:15px}
  .board-corner{font-size:12px;left:10px;bottom:8px}
  .board-footer{font-size:13px}
  .lesson-footer{flex-wrap:wrap;gap:10px}
  .lesson-footer>div{margin-left:auto}
  dialog{padding:25px}
  dialog h2{font-size:25px}
  dialog p,dialog li{font-size:16px}
}

/* Local classroom gate */
.nav-item.locked{color:#a5ada0;background:transparent}
.nav-item.locked:hover{background:#e7ece0;color:#687966}
.nav-item.locked strong{font-weight:500}
.nav-item.locked small{opacity:.75}
.nav-lock{display:grid;place-items:center;margin-left:auto;color:#98a493}
.nav-lock .ui-icon{width:17px;height:17px}
.unlock-label{display:block;font-size:16px;font-weight:600;color:#405d3a;margin:19px 0 8px}
#unlock-code{display:block;width:100%;border:1px solid #cddac5;border-radius:9px;padding:12px 14px;background:#fffef8;color:var(--ink);font-size:19px;letter-spacing:2px;text-transform:uppercase;outline:none}
#unlock-code:focus{border-color:#5f8660;box-shadow:0 0 0 3px #dfead9}
#unlock-code::placeholder{color:#a2ad9e;font-size:14px;letter-spacing:0;text-transform:none}
.unlock-message{min-height:25px;margin-top:8px;color:#ad7640;font-size:14px;line-height:1.6}
.unlock-actions{display:grid;grid-template-columns:1fr 1fr 1.2fr;gap:8px;margin-top:12px}
.unlock-actions button{min-height:44px;font-size:14px}
.unlock-actions .primary-button,.unlock-actions .secondary-button{width:auto}
#unlock-dialog{width:530px}
#unlock-dialog h2{margin-bottom:8px}
#unlock-dialog p{margin-top:0}
@media(max-width:680px){
  .top-actions{gap:2px}
  .unlock-actions{grid-template-columns:1fr 1fr;gap:8px}
  .unlock-actions .primary-button{grid-column:1 / -1;grid-row:1}
  .unlock-actions .secondary-button{grid-row:2}
  #unlock-dialog{width:calc(100vw - 28px)}
  #unlock-code{font-size:18px}
}