:root{color-scheme:dark;--bg:#000;--tile:#161617;--tile2:#1d1d1f;--field:#0d0d0f;--text:#f5f5f7;--muted:#86868b;--soft:#a1a1a6;--line:rgba(255,255,255,.1);--blue:#0071e3;--link:#2997ff;--green:#30d158;--red:#ff6961;--font:-apple-system,BlinkMacSystemFont,"SF Pro Text","Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;--display:-apple-system,BlinkMacSystemFont,"SF Pro Display","Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif;--mono:ui-monospace,"SF Mono",Menlo,Consolas,monospace;--ease:cubic-bezier(.32,.72,0,1)}
*{box-sizing:border-box}[hidden]{display:none!important}body{margin:0;background:var(--bg);color:var(--text);font:17px/1.47 var(--font);letter-spacing:-.01em;-webkit-font-smoothing:antialiased}a{color:inherit;text-decoration:none}button,input,select,textarea{font:inherit}button{cursor:pointer}button:disabled{opacity:.5;cursor:default}button,a,input,select,textarea{touch-action:manipulation}:focus-visible{outline:2px solid var(--link);outline-offset:4px}.wrap{width:min(1080px,100% - 40px);margin-inline:auto}.muted{color:var(--muted);font-size:14px}.eyebrow{font-size:13px;font-weight:500;color:var(--soft);margin:0 0 12px}.gnav{position:sticky;top:0;z-index:10;background:rgba(0,0,0,.78);backdrop-filter:saturate(180%) blur(20px);border-bottom:1px solid rgba(255,255,255,.08)}.nav-in{height:52px;display:flex;gap:16px;align-items:center;font-size:13px}.brand{font-weight:600}.nav-divider{color:#48484a}.nav-labs{display:flex;gap:10px;align-items:center}.beta{font-size:10px;color:var(--muted);border:1px solid var(--line);border-radius:6px;padding:2px 6px}.nav-right{margin-left:auto;color:var(--muted);font-size:12px}.hero{text-align:center;padding:92px 0 82px}.hero .eyebrow{display:flex;justify-content:center;align-items:center;gap:8px;margin-bottom:22px}.blue-dot{width:6px;height:6px;border-radius:50%;background:var(--link);box-shadow:0 0 16px #2997ff66}h1{font:600 clamp(42px,6.9vw,76px)/1.06 var(--display);letter-spacing:-.045em;margin:0}.hero h1 span{color:var(--soft)}.sub{font-size:19px;line-height:1.45;color:var(--muted);margin:24px auto 0}.hero-tags{display:flex;justify-content:center;gap:24px;color:var(--soft);font-size:12px;margin-top:30px}.hero-tags span+span:before{content:"";display:inline-block;width:3px;height:3px;background:#48484a;vertical-align:middle;margin-right:24px;border-radius:50%}h2{font:600 30px/1.15 var(--display);letter-spacing:-.03em;margin:0}.section-head{display:flex;align-items:flex-end;justify-content:space-between;margin-bottom:24px}.section-head .eyebrow{margin-bottom:8px}.section-head .muted{font-size:12px}.test-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:16px}.test-card{background:var(--tile);border:1px solid transparent;border-radius:28px;padding:28px;display:flex;flex-direction:column;align-items:flex-start;text-align:left;min-height:330px;color:var(--text);transition:transform .4s var(--ease),background .3s}.test-card:hover{transform:translateY(-4px);background:var(--tile2)}.card-top{display:flex;align-items:center;justify-content:space-between;width:100%;margin-bottom:30px}.code-icon{width:46px;height:46px;display:grid;place-items:center;background:#2997ff12;color:var(--link);border-radius:14px;font:500 18px var(--mono)}.card-number{color:#636366;font:12px var(--mono)}.subject{font-size:11px;color:var(--muted);margin-bottom:8px}.test-card h3{font:600 25px/1.14 var(--display);letter-spacing:-.025em;margin:0 0 12px}.test-card p{color:var(--muted);font-size:14px;margin:0 0 28px}.card-bottom{margin-top:auto;width:100%;display:flex;justify-content:space-between;align-items:center;border-top:1px solid var(--line);padding-top:18px;font-size:12px;color:var(--soft)}.card-bottom b{font-size:21px;color:var(--link);font-weight:400}.how{display:grid;grid-template-columns:repeat(3,1fr);gap:24px;padding-top:48px;margin-top:48px;border-top:1px solid var(--line)}.how>div{display:flex;gap:14px}.step-num{font-size:12px;color:#636366;font-family:var(--mono);padding-top:3px}.how strong{font-size:14px;font-weight:500}.how p{font-size:12px;color:var(--muted);margin:6px 0}.catalog-note{text-align:center;font-size:12px;color:var(--muted);margin:42px auto 0;line-height:1.7}.foot{display:flex;justify-content:space-between;color:var(--muted);font-size:11px;padding:24px 0 28px;margin-top:80px;border-top:1px solid var(--line)}.pill{display:inline-flex;align-items:center;justify-content:center;gap:14px;min-height:44px;padding:0 22px;border:0;border-radius:999px;background:var(--blue);color:#fff;font-weight:500;font-size:15px;transition:background .25s,transform .25s}.pill:hover{background:#0077ed}.pill:active{transform:scale(.98)}.pill.secondary{background:var(--tile2);color:var(--text)}.pill.secondary:hover{background:#2c2c2e}.pill.small{min-height:36px;font-size:13px;padding:0 16px}.wide{width:100%}.resume{padding:22px 28px;background:var(--tile);border:1px solid #2997ff55;border-radius:22px;display:flex;justify-content:space-between;gap:20px;align-items:center;margin-bottom:40px}.resume strong{font-size:15px}.resume p{margin:4px 0 0;color:var(--muted);font-size:13px}dialog{color:var(--text);background:var(--tile);border:1px solid var(--line);border-radius:30px;padding:36px;width:min(440px,calc(100% - 32px));box-shadow:0 40px 120px #000c;max-height:90svh;overflow-y:auto}dialog::backdrop{background:#000b;backdrop-filter:blur(10px)}dialog form{position:relative}dialog h2{font-size:30px;margin-bottom:12px}dialog .eyebrow{margin-top:20px}.close{position:absolute;right:-12px;top:-16px;width:32px;height:32px;border:0;border-radius:50%;background:var(--tile2);color:var(--soft);font-size:24px}.pin-icon{width:52px;height:52px;border:1px solid var(--line);border-radius:50%;display:grid;place-items:center;color:var(--link);font-size:26px}.field{display:grid;gap:8px;color:var(--soft);font-size:13px;margin-top:20px}.field input{width:100%;height:48px;border:1px solid var(--line);border-radius:12px;background:var(--field);padding:0 14px;color:var(--text);font-size:16px}.field input::placeholder{color:#636366}.form-error{color:var(--red);font-size:13px;min-height:19px;margin:14px 0}.fine{text-align:center;color:var(--muted);font-size:11px;margin-bottom:0}.dialog-actions{display:flex;gap:10px;flex-wrap:wrap;margin-top:24px}.dialog-actions button{flex:1;font-size:13px;padding:0 16px}.work-head{display:flex;justify-content:space-between;gap:24px;align-items:center;padding:52px 0 28px}.work-head h1{font-size:clamp(30px,4vw,46px)}.clock-box{flex:none;text-align:right}.clock-box span{display:block;color:var(--muted);font-size:11px;margin-bottom:5px}.clock-box strong{font:500 32px var(--mono);letter-spacing:-.05em;font-variant-numeric:tabular-nums}.clock-box.warning strong{color:#ff9f0a}.work-bar{display:flex;gap:16px;align-items:center;padding-bottom:24px;border-bottom:1px solid var(--line);margin-bottom:28px}.work-bar>span{margin-left:auto;color:var(--soft);font-size:13px}.text-button{border:0;background:none;color:var(--link);font-size:13px;padding:6px 0}.workspace-grid{display:grid;grid-template-columns:224px minmax(0,1fr);gap:24px}.task-nav h2{font-size:13px;color:var(--muted);font-weight:500;margin:4px 0 16px}.task-nav>p{font-size:12px;color:var(--muted);line-height:1.6;margin:24px 8px}.task-link{display:flex;gap:10px;align-items:center;width:100%;padding:14px 12px;border:1px solid transparent;background:none;color:var(--soft);border-radius:14px;text-align:left;margin-bottom:6px;font-size:13px}.task-link[aria-current=true]{background:var(--tile);border-color:var(--line);color:var(--text)}.task-link:hover{background:var(--tile)}.task-link .n{flex:none;width:25px;height:25px;display:grid;place-items:center;border-radius:50%;background:#ffffff0a;font:11px var(--mono)}.task-link.done .n{background:#30d15818;color:var(--green)}.task-link small{display:block;color:var(--muted);font-size:10px;margin-top:3px}.task-panel{background:var(--tile);border-radius:26px;overflow:hidden;min-width:0}#task-content{padding:30px}.task-meta{color:var(--link);font-size:12px;margin:0 0 10px}.task-panel h2{font-size:28px}.statement{font-size:15px;color:#d2d2d7;white-space:pre-wrap;margin:20px 0;line-height:1.65;overflow-wrap:anywhere}.task-panel h3{font-size:13px;font-weight:600;margin:24px 0 10px}.examples{display:grid;grid-template-columns:1fr 1fr;gap:12px}.example{min-width:0}.example>span{display:block;color:var(--muted);font-size:11px;margin:0 0 8px}.example pre{background:var(--field);border:1px solid var(--line);border-radius:12px;padding:14px;font:13px/1.6 var(--mono);margin:0;overflow:auto}.limits{font-size:11px;color:var(--muted);margin:18px 0 0}.editor-bar{display:flex;align-items:center;gap:12px;padding:12px 20px;background:#1d1d1f;border-top:1px solid var(--line);font-size:12px}.editor-bar label{color:var(--soft)}select{color:var(--text);background:#2c2c2e;border:1px solid var(--line);border-radius:8px;padding:6px 10px;font-size:12px}.editor-bar span{margin-left:auto;font-size:10px;color:var(--muted)}#source{display:block;width:100%;min-height:310px;padding:24px;background:#0d0d0f;color:#e5e5ea;border:0;border-radius:0;resize:vertical;font:14px/1.75 var(--mono);tab-size:4;white-space:pre;overflow:auto;outline-offset:-3px}.editor-hint{font-size:10px;color:var(--muted);padding:10px 20px;margin:0;background:#0d0d0f}.submit-bar{display:flex;justify-content:space-between;align-items:center;gap:16px;padding:20px;border-top:1px solid var(--line)}.submit-bar>span{color:var(--muted);font-size:11px;max-width:220px}.result{padding:0 24px 24px;font-size:13px}.result:empty{display:none}.result-box{border:1px solid var(--line);border-radius:14px;padding:18px;background:#ffffff03}.result-box.good{border-color:#30d15844}.result-box.bad{border-color:#ff9f0a44}.result-title{font-weight:600;font-size:15px}.good .result-title{color:var(--green)}.bad .result-title{color:#ff9f0a}.result-box p{color:var(--soft);margin:6px 0}.result-box pre{white-space:pre-wrap;overflow-wrap:anywhere;color:var(--soft);font:12px/1.6 var(--mono)}.case-row{padding-top:10px;margin-top:10px;border-top:1px solid var(--line);font-size:12px;color:var(--soft)}.option{display:flex;gap:12px;padding:16px;background:var(--field);border:1px solid var(--line);border-radius:12px;margin-top:10px;font-size:15px;cursor:pointer;align-items:baseline}.option:has(input:checked){border-color:var(--link)}.option input{accent-color:var(--blue)}.summary{padding:72px 0}.summary-card{max-width:600px;margin:auto;text-align:center}.summary-mark{display:grid;place-items:center;width:64px;height:64px;margin:24px auto;color:var(--green);border:1px solid #30d15855;border-radius:50%;font-size:28px}.summary h1{font-size:46px}.summary .sub{font-size:16px}.big-score{font:600 64px/1.1 var(--display);letter-spacing:-.05em;margin-top:36px}.big-score small{font-size:26px;color:var(--muted)}#summary-tasks{text-align:left;margin:32px 0;background:var(--tile);border-radius:22px;overflow:hidden}.summary-row{padding:18px 24px;border-bottom:1px solid var(--line);display:flex;justify-content:space-between;font-size:14px;gap:16px}.summary-row:last-child{border:0}.summary-row span{color:var(--soft)}.toast{position:fixed;bottom:24px;left:50%;transform:translateX(-50%);max-width:min(520px,90vw);z-index:100;background:#2c2c2e;color:var(--text);border:1px solid var(--line);border-radius:16px;padding:16px 22px;font-size:14px;box-shadow:0 15px 50px #000b}.skip{position:fixed;top:-100px;left:16px;z-index:100;padding:10px 18px;background:var(--blue);border-radius:10px}.skip:focus{top:10px}.sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip-path:inset(50%)}
.choice-group{border:0;padding:0;margin:0}
@media(min-width:1400px){body:has(#workspace:not([hidden])) .wrap{width:min(1240px,100% - 64px)}}
@media(max-width:850px){.test-grid{grid-template-columns:1fr 1fr}.test-card:last-child{grid-column:1/-1;min-height:270px}.hero{padding:72px 0 64px}.workspace-grid{grid-template-columns:1fr}.task-nav>p,.task-nav h2{display:none}#task-list{display:flex;gap:8px;overflow-x:auto;padding:4px}.task-link{width:auto;min-width:170px;margin:0}.work-head{padding-top:36px}.work-bar{margin-bottom:12px}.workspace-grid{gap:16px}.how{gap:16px}.how>div{gap:8px}.nav-right{display:none}}
@media(max-width:560px){.wrap{width:calc(100% - 32px)}.hero{padding:56px 0 48px}.hero h1{font-size:43px}.sub{font-size:16px}.desktop{display:none}.hero-tags{gap:12px;font-size:10px;flex-wrap:wrap}.hero-tags span+span:before{margin-right:12px}.section-head h2{font-size:26px}.section-head .eyebrow{font-size:11px}.test-grid{grid-template-columns:1fr}.test-card,.test-card:last-child{grid-column:auto;min-height:285px;padding:26px}.card-top{margin-bottom:24px}.how{grid-template-columns:1fr;gap:20px;padding-top:28px;margin-top:32px}.how>div{gap:16px}.catalog-note{text-align:left;margin-top:28px}.foot{margin-top:48px;gap:12px;font-size:10px}.beta{display:none}.resume{flex-direction:column;align-items:stretch;padding:22px}.work-head{align-items:flex-start;gap:12px}.work-head h1{font-size:29px}.clock-box strong{font-size:26px}.clock-box span{font-size:9px}.work-bar{flex-wrap:wrap;gap:12px}.work-bar>span{font-size:11px}.work-bar .pill{margin-left:auto}.task-panel{border-radius:20px}#task-content{padding:22px}.task-panel h2{font-size:25px}.statement{font-size:14px}.examples{gap:8px}.example pre{padding:10px;font-size:12px}.editor-bar{padding:12px;gap:8px}.editor-bar span{display:none}#source{font-size:13px;padding:18px;min-height:280px}.submit-bar{flex-direction:column;align-items:stretch;padding:18px}.submit-bar>span{max-width:none}.result{padding:0 18px 18px}dialog{padding:28px}.summary{padding:48px 0}.summary h1{font-size:36px}.summary-row{padding:16px;font-size:13px}}
@media(prefers-reduced-motion:reduce){*,*::before,*::after{animation:none!important;transition:none!important;scroll-behavior:auto!important}}

#catalog{padding-top:56px}.catalog-title{font-size:32px;letter-spacing:-.03em}
@media(max-width:560px){#catalog{padding-top:32px}.catalog-title{font-size:28px}}

.close{display:grid;place-items:center;padding:0;line-height:1;font-size:0}.close::before,.close::after{content:"";position:absolute;width:12px;height:1.5px;background:currentColor;border-radius:1px;transform:rotate(45deg)}.close::after{transform:rotate(-45deg)}

/* Compact teaching workspace; no UI framework or remote assets. */
:root[data-theme=light]{color-scheme:light;--bg:#f5f6f8;--tile:#fff;--tile2:#edf0f5;--field:#f7f8fa;--text:#202124;--muted:#626b78;--soft:#505866;--line:#18223020;--link:#0065c7;--green:#147d3b;--red:#bf2929}
:root[data-theme=light] .gnav{background:#ffffffed}
:root[data-theme=light] .statement{color:var(--text)}
body:has(#workspace:not([hidden])) .wrap{width:calc(100% - 40px);max-width:1680px}
.work-head{padding:20px 0 12px}.work-head h1{font-size:26px}.work-head .eyebrow{margin-bottom:4px}.clock-box strong{font-size:25px}.work-bar{padding-bottom:12px;margin-bottom:12px}.workspace-grid{display:block}.task-nav{margin-bottom:12px}.task-nav h2,.task-nav>p{display:none}#task-list{display:flex;gap:8px;overflow:auto}.task-link{width:auto;min-width:150px;padding:8px 12px;margin:0}.task-panel{display:grid;grid-template-columns:minmax(240px,30%) minmax(0,1fr);border:1px solid var(--line);border-radius:16px}#task-content{grid-column:1;grid-row:1 / span 3;padding:22px;border-right:1px solid var(--line);max-height:calc(100svh - 230px);overflow:auto}.task-panel h2{font-size:23px}.statement{font-size:14px}.examples{grid-template-columns:1fr}.task-panel #code-section{grid-column:2;min-width:0}.submit-bar,.result{grid-column:2}.task-panel:has(#code-section[hidden]) #task-content{grid-column:1 / -1;border:0;max-height:none}.task-panel:has(#code-section[hidden]) .submit-bar,.task-panel:has(#code-section[hidden]) .result{grid-column:1 / -1}.editor-bar{padding:10px 12px;background:var(--tile2);border-top:0;flex-wrap:wrap;gap:8px}.tool{background:none;color:var(--soft);border:1px solid var(--line);border-radius:7px;padding:5px 9px;font-size:12px;min-height:30px}.tool:hover{color:var(--text);background:var(--tile2)}.editor-settings{font-size:12px}.editor-settings summary{cursor:pointer}.editor-settings>div{display:flex;gap:12px;padding-top:8px}.editor-settings label{display:flex;align-items:center;gap:6px}.inline-notice{font-size:12px;background:var(--tile2);padding:10px 12px;margin:0}.inline-notice .tool{margin-left:8px}#editor-host .cm-editor{height:clamp(280px,43svh,650px);background:var(--field);font-size:inherit}#editor-host{font:14px/1.6 var(--mono)}.cm-scroller{overflow:auto;font-family:var(--mono)!important}.cm-editor.cm-focused{outline:2px solid var(--link);outline-offset:-2px}.editor-hint{display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap;background:var(--field);color:var(--muted)}#source{background:var(--field);color:var(--text)}.run-actions{display:flex;gap:10px;align-items:center;padding:10px 12px;border-top:1px solid var(--line)}.run-actions>span{font-size:11px;color:var(--muted);margin-left:auto}#console-resizer{height:9px;cursor:row-resize;touch-action:none;background:var(--tile2);border-block:1px solid var(--line)}#console-resizer:focus-visible{outline-offset:-2px}.console{height:230px;min-height:140px;overflow:auto;background:var(--field);font-size:12px}.console-tabs{display:flex;gap:4px;border-bottom:1px solid var(--line);padding:4px 8px}.console-tabs [role=tab]{border:0;background:none;color:var(--soft);padding:8px 10px;border-bottom:2px solid transparent;font-size:12px}.console-tabs [aria-selected=true]{border-color:var(--link);color:var(--text)}#clear-console{margin-left:auto}#run-status{margin:10px 14px 4px;color:var(--text)}#run-metrics{margin:4px 14px 10px;font-size:11px;color:var(--muted)}.console pre{margin:0;padding:10px 14px;white-space:pre-wrap;overflow-wrap:anywhere;font:13px/1.6 var(--mono)}#stderr{color:var(--red)}#stdin{display:block;resize:none;width:100%;min-height:100px;border:0;background:transparent;color:var(--text);padding:10px 14px;font:13px/1.6 var(--mono)}.submit-bar{padding:12px}.result{padding:0 12px 12px}.foot{margin-top:28px}
@media(max-width:850px){.task-panel{grid-template-columns:1fr}#task-content{grid-column:1;grid-row:auto;max-height:280px;border-right:0;border-bottom:1px solid var(--line)}.task-panel #code-section,.submit-bar,.result{grid-column:1}.examples{grid-template-columns:1fr 1fr}#editor-host .cm-editor{height:380px}body:has(#workspace:not([hidden])) .wrap{width:calc(100% - 20px)}.work-head h1{font-size:23px}}
@media(max-width:560px){.editor-bar label{display:none}.run-actions>span{max-width:130px}.submit-bar{flex-direction:row;align-items:center}.submit-bar>span{font-size:10px}.submit-bar .pill{font-size:12px;padding:0 14px}.editor-hint{font-size:10px}.task-link{min-width:120px}.work-head{padding-top:16px}.work-head h1{font-size:20px}#editor-host .cm-editor{height:340px}}

.metric-method{margin:4px 14px 8px;font-size:10px;color:var(--muted)}