@import url('https://fonts.googleapis.com/css2?family=DM+Sans:wght@400;450;500;600;650;700&family=Space+Grotesk:wght@400;500;600;700&display=swap');
:root{font-family:'DM Sans',sans-serif;color:#e5e8ed;background:#111316;font-synthesis:none;--muted:#969ca7;--line:#303338;--green:#c9f36b}*{box-sizing:border-box}body{margin:0}button,select,textarea{font:inherit}button,summary,select{cursor:pointer}button{color:inherit}button:focus-visible,select:focus-visible,summary:focus-visible,a:focus-visible{outline:2px solid var(--green);outline-offset:4px}header{height:83px;border-bottom:1px solid var(--line);display:flex;align-items:center;padding:0 34px;gap:30px}.brand{font-family:'Space Grotesk',sans-serif;font-size:39px;font-weight:700;letter-spacing:-3px;text-decoration:none;color:#fff}.brand span{color:var(--green)}.brand-note{font-size:11px;letter-spacing:2px;color:var(--muted)}.header-right{margin-left:auto;display:flex;gap:24px;align-items:center;font-size:13px;color:#b6bdc7}.avatar{border:1px solid #424a37;color:var(--green);background:#23291d;border-radius:50%;height:34px;width:34px;display:grid;place-items:center;font-size:10px}.layout{display:grid;grid-template-columns:253px 1fr;min-height:calc(100vh - 83px)}aside{border-right:1px solid var(--line);padding:34px 17px;display:flex;flex-direction:column}.rail-heading{display:flex;justify-content:space-between;font-size:11px;letter-spacing:1.6px;padding:0 13px}.rail-heading span{color:var(--muted)}.rail-intro{color:var(--muted);font-size:12px;padding:0 13px;margin:10px 0 30px}.group-name{font-size:10px;letter-spacing:1.5px;color:#89929f;margin:25px 13px 12px}.drill{width:100%;display:flex;align-items:center;text-align:left;gap:12px;background:transparent;border:1px solid transparent;border-radius:6px;padding:12px 11px;font-size:13px;margin:3px 0;color:#b3bac5}.drill:hover{background:#202328}.drill.active{background:#252d1d;border-color:#455334;color:var(--green)}.drill .num{font-family:monospace;font-size:11px;opacity:.65}.drill .check{margin-left:auto;color:var(--green)}.rail-footer{margin-top:auto;padding:45px 12px 0;display:flex;gap:10px;color:var(--muted);font-size:12px;line-height:1.7}.rail-footer>span{color:var(--green);font-size:24px}main{padding:39px 38px 20px;min-width:0;max-width:1700px}.intro{display:flex;justify-content:space-between;align-items:center;margin-bottom:33px}.eyebrow{font-size:10px;letter-spacing:1.8px;color:var(--green);font-weight:600}h1{font-family:'Space Grotesk',sans-serif;font-size:clamp(24px,2.3vw,36px);letter-spacing:-1.2px;font-weight:500;margin:11px 0 9px}.intro p{color:var(--muted);font-size:14px;margin:0}.session{border-left:1px solid var(--line);padding:0 0 0 28px;margin-left:20px;display:flex;flex-direction:column;gap:5px}.session b{font-family:'Space Grotesk',sans-serif;font-size:36px;font-weight:400}.session span{font-size:9px;letter-spacing:1px;color:var(--muted);white-space:nowrap}.workspace{border:1px solid #373b41;border-radius:10px;display:grid;grid-template-columns:44% 56%;overflow:hidden;background:#191c20}.problem{border-right:1px solid #373b41;min-width:0}.section-top{height:55px;padding:0 23px;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;gap:10px;font-size:10px;letter-spacing:1.3px;color:#b4bbc5}.pill{color:var(--green);font-size:9px;border:1px solid #4d5b39;border-radius:20px;padding:5px 8px;white-space:nowrap}.problem-content{padding:29px 26px}h2{font-family:'Space Grotesk',sans-serif;font-size:28px;letter-spacing:-.8px;line-height:1.2;margin:12px 0 17px;font-weight:500}.problem-content>p{font-size:15px;line-height:1.7;color:#b6bcc5}.contract{margin:25px 0;display:flex;flex-direction:column;gap:18px;border-left:2px solid #444c37;padding-left:15px}.contract span,.example span{font-size:10px;letter-spacing:1.2px;color:var(--muted)}.contract p{margin:6px 0 0;font-size:14px;line-height:1.5;color:#d3d7df}h3{font-size:14px;font-weight:500;margin:0 0 13px}.example{border:1px solid var(--line);border-radius:6px;background:#131619}.example>div{padding:14px 17px}.example>div+div{border-top:1px solid var(--line)}pre{font-family:ui-monospace,SFMono-Regular,Consolas,monospace;font-size:13px;white-space:pre-wrap;overflow-wrap:anywhere;line-height:1.6;margin:8px 0 0}.example pre{color:#d9e9bc}.problem-content .example-note{font-size:12px;color:var(--muted);margin:12px 0 27px}.help{border-top:1px solid var(--line);padding-top:23px}.help-heading{display:flex;justify-content:space-between}.help-heading span{font-size:11px;color:var(--muted)}.help p{font-size:12px;color:var(--muted);line-height:1.6;margin:0 0 16px}.secondary{width:100%;background:#25292e;border:1px solid #3b4149;border-radius:5px;padding:12px 14px;text-align:left;font-size:13px}.secondary span{float:right;color:var(--muted);font-size:11px}#hints{font-size:14px;line-height:1.7;color:#c4cbb5;padding-left:21px}#hints li{margin-bottom:10px}details{margin-top:20px;font-size:12px;color:#a5adb8}details p{margin-top:15px!important}details pre{color:#d4e9b1;background:#111416;padding:12px}.coding{min-width:0;display:flex;flex-direction:column}.section-top select{background:#25292e;border:1px solid #41464e;border-radius:4px;color:#d4d9e2;padding:6px 10px;font-size:12px}.editor-toolbar{display:flex;justify-content:space-between;background:#131619;border-bottom:1px solid #252a30;padding:14px 23px;font-size:12px;color:#c7cdd6}.editor-toolbar button{background:none;border:0;color:#929ba7;font-size:11px}.editor{display:flex;background:#111417;height:305px;padding:21px 0}.editor pre{margin:0;text-align:right;width:52px;flex-shrink:0;padding-right:16px;color:#555d67;overflow:hidden;line-height:24px;font-size:13px;user-select:none}.editor textarea{background:transparent;outline:0;border:0;color:#d5e8bb;resize:none;width:100%;padding:0 20px 0 0;tab-size:4;font:13px/24px ui-monospace,SFMono-Regular,Consolas,monospace;white-space:pre;overflow:auto}.editor:focus-within{box-shadow:inset 0 0 0 1px #596d3b}.editor-footer{display:flex;justify-content:space-between;gap:12px;background:#111417;padding:10px 20px;font-size:10px;color:#727d8b}.run-bar{padding:17px 22px;display:flex;justify-content:space-between;align-items:center;border-top:1px solid var(--line);border-bottom:1px solid var(--line)}.run-bar>span{font-size:12px;color:var(--muted)}.primary{background:var(--green);border:0;color:#17200d;border-radius:5px;padding:11px 19px;font-weight:650;font-size:13px}.primary:hover{background:#d8ff86}button:disabled{opacity:.5;cursor:wait}.results{padding:23px;flex:1;min-height:210px}.results-heading{display:flex;justify-content:space-between}.results-heading span{font-size:11px;color:var(--muted)}.empty{padding:21px 0;text-align:center;color:#858e9b}.empty>span{font-size:27px;color:#515a66}.empty p{font-size:13px;margin:12px 0 7px}.empty small{font-size:11px}.test{padding:12px;border:1px solid var(--line);border-radius:5px;margin:9px 0;font-size:12px}.pass{color:var(--green)}.fail{color:#ffb1a8}.test pre{color:#c4cbd5;font-size:12px}.error{white-space:pre-wrap;color:#ffb1a8;font-size:13px;line-height:1.6;overflow-wrap:anywhere}#next{margin-top:15px}footer{display:flex;justify-content:space-between;gap:20px;margin-top:22px;font-size:9px;letter-spacing:1px;color:#737c89}footer span{letter-spacing:0;font-size:11px}[hidden]{display:none!important}@media(min-width:1500px){.editor{height:350px}.problem-content{padding:35px}.drill{font-size:14px;padding:14px 11px}}@media(max-width:1100px){.layout{grid-template-columns:205px 1fr}main{padding:28px 20px}.workspace{grid-template-columns:45% 55%}.session{display:none}.problem-content{padding:22px 18px}.section-top{padding:0 17px}.run-bar>span{display:none}.run-bar{justify-content:flex-end}.editor-footer span:last-child{display:none}}@media(max-width:780px){header{height:65px;padding:0 20px}.brand-note{display:none}.layout{display:block}aside{padding:16px;border-right:0;border-bottom:1px solid var(--line)}.rail-heading,.rail-intro,.group-name,.rail-footer{display:none}nav{display:flex;overflow:auto;gap:8px}.drill{flex-shrink:0;width:auto;white-space:nowrap}.intro{margin-bottom:24px}h1{font-size:28px}.intro p{line-height:1.6}.workspace{grid-template-columns:1fr}.problem{border-right:0;border-bottom:1px solid var(--line)}.editor{height:320px}.section-top{font-size:11px}main{padding:25px 16px}.problem-content{padding:25px}.rail-heading{font-size:12px}footer{line-height:1.7;flex-direction:column}.editor textarea{font-size:14px}.header-right{font-size:12px}.help p,.example-note,.drill{font-size:14px}}

/* Keep the editing surface inside the visible phone viewport, above its keyboard. */
.mobile-tabs,.mobile-brief,.coding-keys{display:none}
@media(max-width:780px){
 body{position:fixed;top:var(--phone-top,0px);left:0;right:0;height:var(--phone-height,100dvh);display:flex;flex-direction:column;overflow:hidden;padding-top:env(safe-area-inset-top)}
 header{height:48px;min-height:48px;padding:0 16px}.brand{font-size:31px}.avatar{display:none}
 .layout{display:flex;flex:1;min-height:0;flex-direction:column}aside{padding:5px 10px;flex-shrink:0}nav{gap:6px}.drill{padding:10px;min-height:44px;font-size:14px;margin:0}
 main{display:flex;flex:1;min-height:0;flex-direction:column;padding:0 10px max(6px,env(safe-area-inset-bottom));width:100%}.intro,footer{display:none}
 .mobile-tabs{display:flex;flex-shrink:0;gap:4px;padding:7px 0}.mobile-tabs button{flex:1;min-height:44px;border:1px solid var(--line);border-radius:6px;background:#1b1f23;font-size:14px}.mobile-tabs button[aria-pressed=true]{background:#303d22;border-color:#697e46;color:var(--green)}#mobile-status{font-size:12px}
 .mobile-brief{display:flex;flex-direction:column;gap:4px;padding:5px 3px 9px;flex-shrink:0;min-width:0}.mobile-brief strong{font-size:15px;font-weight:500}.mobile-brief span{font-family:monospace;font-size:12px;white-space:nowrap;overflow:auto;max-height:30px;color:#b5c69d}
 body:not([data-mobile-view=code]) .mobile-brief{display:none}
 .workspace{display:flex;flex-direction:column;flex:1;min-height:0;border-radius:7px;overflow:hidden}.problem{display:none;border:0;overflow:auto;overscroll-behavior:contain;min-height:0}.coding{flex:1;min-height:0;overflow:hidden}
 .workspace[data-view=question] .problem{display:block}.workspace[data-view=question] .coding{display:none}
 .workspace[data-view=code] .results{display:none}
 .workspace[data-view=results] .coding>*:not(.results){display:none}
 .workspace[data-view=results] .results{display:block;overflow:auto;min-height:0;padding:18px;overscroll-behavior:contain}
 .section-top{min-height:45px;height:45px;flex-shrink:0;padding:0 12px;font-size:12px}.section-top select{font-size:16px;min-height:36px;padding:4px 8px}
 .editor-toolbar{padding:0 12px;min-height:38px;align-items:center;flex-shrink:0}.editor-toolbar button{min-height:38px;font-size:12px}
 .editor{height:auto;flex:1;min-height:65px;padding:10px 0;overflow:hidden}.editor textarea{font-size:16px;line-height:25px;padding-right:10px;overscroll-behavior:contain}.editor pre{width:35px;padding-right:8px;line-height:25px;font-size:12px}
 .coding-keys{display:flex;flex-shrink:0;overflow-x:auto;gap:5px;padding:5px 7px;border-top:1px solid var(--line);background:#1b2025}.coding-keys button{min-width:40px;min-height:40px;padding:5px;border:1px solid #444d58;border-radius:5px;background:#292f36;color:#e4e9ef;font:15px monospace;touch-action:manipulation}
 .editor-footer{padding:5px 10px;flex-shrink:0;font-size:12px}.run-bar{padding:7px 10px;flex-shrink:0}.run-bar .primary{min-height:44px;width:100%;font-size:15px}
 .problem-content{padding:20px}.problem-content>p{font-size:16px}.contract p{font-size:16px}.help p{font-size:14px}.secondary{min-height:44px;font-size:14px}summary{padding:10px 0;font-size:14px}.results-heading{align-items:center;gap:8px}.results-heading span{font-size:13px}.test{font-size:14px}.test pre{font-size:14px}.empty small{font-size:14px}
 .keyboard-open header,.keyboard-open aside,.keyboard-open .editor-toolbar,.keyboard-open .editor-footer{display:none}.keyboard-open .mobile-tabs{padding:3px 0}.keyboard-open .mobile-tabs button{min-height:36px}.keyboard-open .mobile-brief{padding:2px 3px 5px}.keyboard-open .mobile-brief strong{display:none}.keyboard-open .section-top{min-height:38px;height:38px}.keyboard-open .coding-keys{padding:3px 5px}.keyboard-open .coding-keys button{min-height:36px}.keyboard-open .run-bar{padding:4px 8px}.keyboard-open .run-bar .primary{min-height:38px;padding:6px}
}