@charset "UTF-8";
:root{--navy:#0f172a;--deep:#07111f;--blue:#60a5fa;--purple:#a78bfa;--ink:#18263a;--muted:#5b6c82;--line:#dbe3ee;--page:#f3f6fa;--card:#fff;--success:#18734d;--danger:#af2838;--radius:14px}
*{box-sizing:border-box}body{margin:0;background:var(--page);color:var(--ink);font:16px/1.7 -apple-system,BlinkMacSystemFont,"PingFang SC","Microsoft YaHei",sans-serif}button,input,textarea{font:inherit}button,a,input,textarea,summary{touch-action:manipulation}button{cursor:pointer;min-height:42px;border:0;border-radius:8px;padding:9px 14px;line-height:1.4}button:disabled{opacity:.48;cursor:not-allowed}a{color:#245ea8;text-underline-offset:3px}button:focus-visible,a:focus-visible,summary:focus-visible,textarea:focus-visible,input:focus-visible{outline:3px solid #508ff0;outline-offset:3px}button:hover:not(:disabled){filter:brightness(.95)}h1,h2,h3,p{margin:0}h1{font-size:30px;line-height:1.4;letter-spacing:-.8px}h2{font-size:21px;line-height:1.5}h3{font-size:17px}p+p{margin-top:12px}code,pre,textarea#code{font-family:"SFMono-Regular",Consolas,"Liberation Mono",monospace}code{font-size:.91em;background:#eef2f7;padding:2px 6px;border-radius:4px}pre{margin:0;line-height:1.75;font-size:14px}summary{cursor:pointer;font-weight:600;min-height:42px;padding:8px 0}details>p{margin:6px 0 12px}details[open]>summary{margin-bottom:8px}[hidden]{display:none!important}.skip{position:absolute;top:-60px;left:16px;z-index:20;padding:8px;background:#fff}.skip:focus{top:10px}.quiet{background:transparent;color:var(--muted);border:1px solid var(--line)}.primary{background:#225cc2;color:#fff;font-weight:600}.secondary{background:#e8effd;color:#214c99;border:1px solid #c5d6f4;font-weight:600}.danger{background:#fff1f1;color:var(--danger);border:1px solid #ecc8cd}.small{min-height:30px;padding:4px 9px;font-size:12px;color:var(--muted);background:transparent;border:1px solid var(--line)}.eyebrow{font-size:12px;letter-spacing:1.5px;font-weight:650;color:var(--muted)}.topbar{height:78px;background:var(--navy);color:#fff;display:flex;align-items:center;gap:24px;padding:0 32px;border-bottom:1px solid #24324a}.brand{display:flex;align-items:center;gap:12px;color:#fff;text-decoration:none;font-weight:700;font-size:18px;line-height:1.3}.brand-sub{display:block;font-size:12px;font-weight:400;letter-spacing:2px;color:#b5c5da}.brand-symbol{display:grid;place-items:center;border:1px solid #416188;border-radius:12px;background:#1c304a;color:var(--blue);font:700 23px/1 monospace;width:43px;height:43px}.top-note{margin-left:auto;font-size:13px;color:#b9c7da}.topbar .quiet{border-color:#3a4b66;color:#d8e3f0}.shell{display:grid;grid-template-columns:256px minmax(0,1fr);max-width:1600px;margin:auto;min-height:calc(100vh - 78px)}.sidebar{background:var(--deep);color:#dae3ef;padding:26px 18px;display:flex;flex-direction:column;gap:14px}.sidebar-heading{display:flex;justify-content:space-between;align-items:center;font-size:12px}.sidebar .eyebrow{color:#a6b6cd}.progress-track{height:4px;background:#20304a;border-radius:9px;overflow:hidden;margin:0 5px 8px}.progress-track span{height:100%;display:block;width:0;background:var(--blue);transition:width .3s}.nav-group{font-size:10px;font-weight:600;letter-spacing:2px;color:#8da4c4;padding:13px 10px 7px}.lesson-link{position:relative;display:flex;align-items:center;gap:10px;border-radius:9px;color:#c5d1e2;font-size:13px;text-decoration:none;padding:10px 10px;min-height:46px;margin-bottom:3px;line-height:1.45;border:1px solid transparent}.lesson-link:hover{background:#13223a}.lesson-link.active{background:#192d49;border-color:#344d74;color:#fff}.lesson-num{font:500 12px/1 monospace;color:#95aaca;min-width:22px}.lesson-link.active .lesson-num{color:var(--blue)}.nav-done{font-size:13px;color:#71d2ad;margin-left:auto}.sidebar-bottom{margin-top:auto;padding:18px 8px 0;color:#9eb1ca;font-size:12px;border-top:1px solid #22324a}.sidebar-bottom .quiet{font-size:12px;color:#b9c7da;border-color:#3a4b66;margin-top:12px;width:100%}main{min-width:0;padding:30px 40px 20px;max-width:1330px}.lesson-head{display:flex;align-items:flex-start;justify-content:space-between;gap:18px;margin-bottom:22px}.lesson-head .eyebrow{display:block;margin-bottom:7px}.lesson-head p{margin-top:9px;color:var(--muted);font-size:14px}.status-pill{white-space:nowrap;font-size:12px;background:#e7edf6;color:#4b668b;padding:6px 11px;border-radius:25px;margin-top:6px}.status-pill.complete{color:var(--success);background:#e2f4ea}.tabs{display:flex;gap:4px;border-bottom:1px solid var(--line);margin-bottom:24px}.tabs button{padding:11px 17px 14px;border-radius:7px 7px 0 0;background:transparent;font:600 12px/1.5 monospace;color:#77879d;position:relative;white-space:nowrap}.tabs button span{font-family:-apple-system,BlinkMacSystemFont,"PingFang SC",sans-serif;font-size:14px;margin-left:7px}.tabs button[aria-selected="true"]{color:#245caf;background:#e7eefb}.tabs button[aria-selected="true"]:after{content:"";position:absolute;bottom:-1px;height:3px;left:12px;right:12px;background:#3979d3;border-radius:3px}.panel{animation:enter .18s ease}.story-card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:24px 28px;position:relative;overflow:hidden}.story-card:before{content:"";position:absolute;top:0;left:0;bottom:0;width:4px;background:#518ceb}.story-card .eyebrow{color:#3362a5}.story-card h2{margin:9px 0 12px}.story-card>p{color:#53657c;font-size:15px}.goal-line{margin-top:18px;padding-top:14px;border-top:1px solid #edf0f5;font-size:13px;color:var(--muted)}.prediction{margin-top:22px;border:1px solid #c9d7ee;background:#eaf0fb;border-radius:var(--radius);padding:18px 22px}.prediction p{margin:8px 0 12px;font-size:14px}.prediction textarea{width:100%;resize:vertical;min-height:70px;background:#fff;border:1px solid #c0cfe5;border-radius:8px;padding:10px;font-size:14px}.prediction small{font-size:11px;color:var(--muted)}.section-title{display:flex;align-items:center;justify-content:space-between;margin:28px 0 14px;gap:10px}.section-title span{font-size:12px;color:var(--muted)}.concept-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(100%,230px),1fr));gap:14px}.concept-card{padding:20px;background:#fff;border:1px solid var(--line);border-radius:var(--radius)}.concept-card h3{margin-bottom:9px}.concept-card p{font-size:14px;color:var(--muted)}.concept-card pre{background:#f1f4f9;padding:10px 12px;border-radius:8px;overflow-x:auto;margin-top:14px;font-size:13px;color:#244466}.worked{border:1px solid var(--line);border-radius:var(--radius);background:#fff;padding:22px 26px}.worked-list{list-style:none;margin:0;padding:0}.worked-list li{display:flex;gap:16px;padding:10px 0}.step-num{display:grid;place-items:center;flex-shrink:0;width:29px;height:29px;background:#edf2fb;color:#3162af;border-radius:50%;font-size:12px;font-weight:700}.worked-list h3{font-size:15px;margin-bottom:3px}.worked-list p{font-size:14px;color:var(--muted)}.tip-card{border-left:3px solid #ac9bd2;padding:14px 20px;background:#efecf6;margin:22px 0;border-radius:0 9px 9px 0;font-size:14px}.tip-card p{margin-top:5px;color:#5c5670}.next-row{display:flex;justify-content:flex-end;margin:24px 0}.task-card{padding:17px 22px;border:1px solid var(--line);background:#fff;border-radius:var(--radius);margin-bottom:18px;font-size:14px}.task-card>p{margin-top:7px;font-size:15px}.task-card details{border-top:1px solid #edf0f5;margin-top:12px}.lab{display:grid;grid-template-columns:minmax(0,1.3fr) minmax(0,1fr);gap:18px}.editor-card{overflow:hidden;border:1px solid var(--line);border-radius:var(--radius);background:#fff}.editor-top{background:#edf1f7;display:flex;align-items:center;justify-content:space-between;padding:10px 15px;font:12px/1.5 monospace;color:#586d86}.dot{display:inline-block;width:7px;height:7px;border-radius:50%;background:#488ad5;margin-right:9px}.code-area{display:flex;background:#111e32;height:325px;overflow:hidden}.code-area #line-numbers{padding:17px 10px 17px 14px;color:#758aa8;text-align:right;font:14px/25px monospace;min-width:40px;white-space:pre;overflow:hidden;background:#0d192b;user-select:none}#code{resize:none;flex:1;min-width:0;width:100%;background:transparent;color:#edf3fc;border:0;border-radius:0;outline-offset:-3px;padding:17px 15px;line-height:25px;font-size:14px;tab-size:4;white-space:pre;overflow:auto}#code:focus{outline:2px solid #568ee0}#stdin{width:calc(100% - 30px);margin:6px 15px 10px;border:1px solid #c5d0e0;background:#f8fafd;border-radius:7px;font-family:monospace;font-size:13px;line-height:1.5;resize:vertical;min-height:67px;padding:9px 12px}.editor-help{display:flex;align-items:center;gap:8px;padding:8px 12px;color:var(--muted);font-size:10px;border-bottom:1px solid #e5eaf2;flex-wrap:wrap}.editor-help span{margin-right:auto}.input-label{display:block;font-size:12px;font-weight:600;padding:12px 15px 0}.input-label span{font-weight:400;font-size:10px;margin-left:4px;color:var(--muted)}.run-toolbar{display:flex;gap:8px;padding:0 15px 12px;flex-wrap:wrap}.run-toolbar button{font-size:13px}.runtime-status{font-size:11px;color:var(--muted);padding:0 15px 13px;min-height:30px}.output-card{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:18px;min-width:0}.output-top{display:flex;align-items:center;gap:10px;justify-content:space-between;margin-bottom:15px}.output-top h2{font-size:15px}.output-top span{font-size:11px;color:var(--muted)}#stdout{background:#f1f4f8;min-height:220px;padding:16px;border-radius:8px;font-size:13px;color:#24405f;white-space:pre-wrap;word-break:break-word;max-height:420px;overflow:auto}.error-hint{border:1px solid #efd4c1;background:#fff6ea;color:#8f5423;padding:12px;margin-top:12px;font-size:13px;border-radius:7px}.check-result{margin-top:14px;padding:12px;background:#e6f4ed;border:1px solid #c1e1ce;color:#1b6c49;border-radius:9px;font-size:13px}.check-result.fail{background:#fff0f1;border-color:#ebc9ce;color:#922e3c}.case-result{border-bottom:1px solid #e6ebf2;padding:10px 0;font-size:12px}.case-result pre{font-size:11px;white-space:pre-wrap;overflow-wrap:anywhere;color:#53657c}.case-result summary{font-size:12px;padding:5px 0;min-height:32px}.test-explain{margin-top:20px;font-size:13px;color:var(--muted);border:1px solid var(--line);padding:12px 20px;background:#fff;border-radius:12px}.test-case{margin:9px 0;padding:9px 12px;background:#f3f6fb;border-radius:8px;font-size:12px}.quiz-intro{padding:21px 25px;background:#fff;border:1px solid var(--line);border-radius:var(--radius);margin-bottom:18px}.quiz-intro p{color:var(--muted);font-size:14px;margin-top:8px}.quiz-card{border:1px solid var(--line);background:#fff;border-radius:var(--radius);padding:22px 24px;margin-bottom:16px}.quiz-card legend{font-weight:600;font-size:15px;padding:0;float:left;width:100%;margin-bottom:14px;white-space:pre-wrap}.quiz-card .options{clear:both;display:grid;gap:8px}.option-label{display:flex;align-items:flex-start;gap:10px;font-size:14px;border:1px solid var(--line);border-radius:8px;padding:10px 13px;cursor:pointer;min-height:44px;white-space:pre-wrap}.option-label:has(input:checked){background:#ebf1fc;border-color:#729ada;color:#214f99}.option-label input{margin:6px 0 0;accent-color:#2865cb}.quiz-feedback{margin-top:14px;background:#e7f5ed;border-radius:8px;font-size:13px;padding:12px 15px;color:#226b4b}.quiz-feedback.wrong{background:#fff5e6;color:#835d28}.quiz-actions{display:flex;gap:12px;align-items:center;flex-wrap:wrap}.quiz-score{font-size:14px;font-weight:600;color:#37567d}.self-check{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:20px 24px;margin-top:25px}.self-check p{font-size:13px;color:var(--muted);margin:8px 0 12px}.self-check label{display:flex;gap:10px;margin:10px 0;font-size:13px;align-items:flex-start}.self-check input{margin-top:5px;accent-color:#2865cb}.completion-note{margin-top:16px;font-size:13px;color:var(--muted);padding:13px;border-radius:9px;background:#edf2f8}.lesson-footer{display:flex;align-items:center;justify-content:space-between;gap:12px;border-top:1px solid var(--line);padding-top:20px;margin-top:36px;color:#8491a2;font-size:11px}.lesson-footer button{font-size:12px}.save-warning{padding:10px 25px;font-size:13px;background:#fff1d5;color:#7c591d}.interactive-lab{margin-top:24px;border:1px solid var(--line);background:#fff;border-radius:var(--radius);padding:22px 25px}.interactive-lab h3{font-size:18px}.interactive-lab p{font-size:13px;color:var(--muted);margin:8px 0 14px}.simulation-tools{display:flex;align-items:center;gap:12px;flex-wrap:wrap;font-size:13px}.simulation-tools input,.simulation-tools select{min-height:36px;border-radius:7px;border:1px solid #c7d2e1;padding:4px 8px;font-size:13px;max-width:100%}.simulation-tools input[type=number]{width:92px}.simulation-tools label{display:flex;align-items:center;gap:7px}.chart{width:100%;height:auto;display:block;margin-top:18px}.sim-answer{font-size:14px;background:#edf3fc;color:#315c9b;padding:11px 14px;border-radius:8px;margin-top:14px;white-space:pre-wrap}.hanoi-board{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin:22px 0 12px}.tower{height:172px;position:relative;background:#f1f5fb;border:1px solid #d6e0ef;border-radius:9px;padding:0;display:flex;flex-direction:column;align-items:center;justify-content:flex-end;padding-bottom:19px}.tower::before{content:"";width:5px;height:113px;background:#a7b7cc;position:absolute;bottom:19px;border-radius:6px}.tower::after{content:"";position:absolute;bottom:15px;left:10%;right:10%;height:6px;background:#a7b7cc;border-radius:4px}.tower.selected{border:2px solid #3978d0;background:#e6eefc}.tower-label{position:absolute;top:8px;font-size:12px;color:#6c7f97}.disk{display:block;height:20px;border-radius:4px;border:1px solid #3979c8;flex-shrink:0;z-index:1;margin-bottom:2px;font:600 10px/18px monospace;color:#183252}.hanoi-message{min-height:48px;font-size:13px;color:#536a89;padding:9px 0}.stair-path{display:flex;gap:7px;flex-wrap:wrap;align-items:center;margin-top:18px}.path-chip{padding:5px 9px;background:#e8effb;border-radius:6px;font-size:12px;color:#355b8d}.stair-count{font-size:13px;color:#687d98;margin-top:12px}.graph-row{display:flex;gap:8px;align-items:center;flex-wrap:wrap;font-size:12px}.graph-row span{padding:6px 10px;border:1px solid #c4d4eb;border-radius:7px;color:#47678e;background:#f4f7fc}.graph-row i{color:#8394af;font-style:normal}dialog{width:min(680px,calc(100% - 30px));max-height:85vh;border:1px solid #c7d3e4;border-radius:17px;padding:0;background:#fff;color:var(--ink)}dialog::backdrop{background:#07111fb3}.dialog-head{padding:18px 24px;border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;gap:12px}.dialog-head h2{font-size:20px}.dialog-content{padding:24px;font-size:14px;overflow:auto;max-height:calc(85vh - 86px)}.dialog-content ol{padding-left:22px;margin:16px 0}.dialog-content details{margin-top:16px}.reset-area{border-top:1px solid var(--line);margin-top:22px;padding-top:18px}.reset-area button{font-size:12px}@keyframes enter{from{opacity:.4;transform:translateY(4px)}to{opacity:1;transform:translateY(0)}}
@media(min-width:1300px){main{padding-left:50px;padding-right:50px}.sidebar{padding-left:22px;padding-right:22px}}
@media(max-width:1050px){.shell{grid-template-columns:222px minmax(0,1fr)}main{padding:25px}.lab{grid-template-columns:1fr}.code-area{height:315px}#stdout{min-height:130px}.topbar{padding:0 24px}.concept-grid{grid-template-columns:repeat(2,minmax(0,1fr))}}
@media(max-width:700px){.topbar{height:68px;padding:0 15px;gap:12px}.brand{font-size:16px;gap:8px}.brand-symbol{width:37px;height:37px;font-size:21px}.top-note{display:none}.topbar .quiet{margin-left:auto;font-size:12px;padding:8px 10px}.shell{display:block}.sidebar{padding:13px 13px 10px;gap:7px}.sidebar-heading{padding:0 4px}.progress-track{margin:0 4px}.sidebar nav{display:flex;overflow-x:auto;gap:6px;padding:4px 0;scrollbar-width:thin}.nav-group,.sidebar-bottom{display:none}.lesson-link{flex-shrink:0;margin:0;font-size:12px;padding:8px 10px;min-height:42px}.lesson-link:not(.active) .lesson-link-title{display:none}.lesson-num{min-width:17px}.nav-done{margin-left:3px}main{padding:23px 16px}.lesson-head{margin-bottom:17px;gap:8px}h1{font-size:24px}.lesson-head p{font-size:12px}.lesson-head .eyebrow{font-size:10px}.status-pill{font-size:10px;padding:5px 8px;margin-top:2px}.tabs{margin-bottom:18px}.tabs button{padding:10px 10px 12px;flex:1;font-size:10px}.tabs button span{font-size:12px;margin-left:4px}.story-card{padding:20px}.story-card h2{font-size:18px}.story-card>p{font-size:14px}.prediction{padding:16px}.concept-grid{grid-template-columns:1fr}.concept-card{padding:18px}.worked{padding:18px}.worked-list{font-size:13px}.step-num{width:25px;height:25px}.worked-list li{gap:11px}.section-title h2{font-size:19px}.task-card{padding:15px 18px}.code-area{height:300px}#code{font-size:13px;padding-left:10px}.code-area #line-numbers{font-size:13px;padding-left:8px;min-width:34px}.run-toolbar{gap:6px;padding-left:11px;padding-right:11px}.run-toolbar button{padding:9px 10px;font-size:12px}.output-card{padding:15px}.input-label span{display:block;margin:2px 0 0}.quiz-card{padding:18px 16px}.quiz-card legend{font-size:14px}.option-label{font-size:13px;padding:9px 11px}.self-check{padding:18px}.interactive-lab{padding:18px 15px}.tower{height:150px}.hanoi-board{gap:7px}.lesson-footer{flex-wrap:wrap;font-size:10px}.lesson-footer>span{order:3;width:100%;text-align:center}.dialog-content{padding:19px}.dialog-head{padding:15px 19px}.simulation-tools{gap:8px}}
@media(prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important;scroll-behavior:auto!important}}
.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}.audio-note{margin-top:14px;border-top:1px solid #edf0f5}.audio-note summary{font-size:13px;color:#536985}.self-check label{cursor:pointer;min-height:32px}
@media print{.topbar,.sidebar,.tabs,.lesson-footer,.next-row,button,dialog{display:none!important}.shell{display:block}main{padding:0}.panel[hidden]{display:block!important}.code-area{height:auto;min-height:250px;background:#fff}#code{color:#000}body{background:#fff}}

.site-course-return{background:#0f172a;padding:7px 32px;border-bottom:1px solid #2d3b50;font-size:12px}.site-course-return a{color:#c0d1e8;text-decoration:none}.site-course-return a:hover{text-decoration:underline}@media(max-width:700px){.site-course-return{padding:7px 16px}.brand{font-size:15px}}

.course-reference{margin-top:18px;font-size:14px}.course-reference a{display:inline-block;padding:8px 0;min-height:44px}

.full-lesson-details{margin-top:26px;border:1px solid var(--line);border-radius:14px;padding:14px 18px;background:#fff}.full-lesson-details>summary{color:#365a88;font-size:14px}.full-lesson-content{padding-top:18px}.full-lesson-content .story-card{border:0;background:#f4f7fc}.brand-sub{letter-spacing:.3px}@media(max-width:700px){.brand-sub{font-size:10px}.full-lesson-details{padding:12px}.full-lesson-details>summary{font-size:13px}}