:root{color-scheme:dark;--bg:#0b1220;--panel:#111c2e;--panel2:#162338;--line:#27384f;--text:#e8eef7;--muted:#a9bad0;--mint:#6ce5ca;--blue:#75b5ff;--amber:#ffce79;--ink:#0b2423}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--text);font:16px/1.65 -apple-system,BlinkMacSystemFont,"Segoe UI","Microsoft YaHei",sans-serif}button,select,input{font:inherit}button,select{color:var(--text);background:var(--panel2);border:1px solid var(--line);border-radius:7px;padding:7px 13px;cursor:pointer}button:hover{border-color:var(--mint)}button:disabled{opacity:.35;cursor:default}a{color:inherit;text-decoration:none}button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible{outline:2px solid var(--amber);outline-offset:3px}[hidden]{display:none!important}.topbar{height:82px;border-bottom:1px solid var(--line);display:flex;align-items:center;padding:0 32px;gap:36px;background:#0f1828}.brand{display:flex;gap:13px;align-items:center;font-weight:700;line-height:1.1;font-size:21px}.brand svg{width:32px;height:34px;fill:var(--mint);stroke:var(--mint);stroke-width:1.6}.brand-sub{display:block;font-size:12px;letter-spacing:3px;color:var(--muted);margin-top:7px}.top-note{color:var(--muted);font-size:14px}.mobile-menu{display:none;margin-left:auto}.layout{display:grid;grid-template-columns:240px minmax(0,1fr);max-width:1700px;margin:auto}aside{border-right:1px solid var(--line);padding:32px 18px;position:sticky;top:0;align-self:start;height:calc(100vh - 82px);overflow-y:auto}.nav-heading{color:var(--muted);font-size:14px;letter-spacing:2px;padding:0 14px 18px}.nav-section{font-size:12px;color:var(--mint);margin:22px 14px 8px;letter-spacing:1px}.nav-link{display:flex;align-items:center;gap:12px;padding:10px 14px;margin:4px 0;border-radius:7px;color:var(--muted);font-size:15px}.nav-link .num{font:12px ui-monospace,monospace;opacity:.7}.nav-link.active{background:#1a3440;color:var(--mint)}.nav-link:hover{background:var(--panel2);color:var(--text)}.nav-tip{font-size:14px;color:var(--muted);padding:24px 14px;border-top:1px solid var(--line);margin-top:30px}.source-link{display:block;color:var(--blue);font-size:14px;padding:0 14px}main{padding:30px 36px 0;min-width:0}.breadcrumb{font-size:13px;color:var(--muted);margin-bottom:13px}.lesson-heading{display:flex;justify-content:space-between;gap:20px}h1{font-size:30px;line-height:1.3;margin:0 0 10px;letter-spacing:-.6px}.lesson-heading p{max-width:790px;margin:0;color:var(--muted)}.lesson-number{font:64px/1 ui-monospace,monospace;color:#2a415c;font-weight:700}h2{font-size:19px;line-height:1.5;margin:5px 0 12px}h3{font-size:13px;font-weight:500;color:var(--muted);margin:0 0 8px}.concept-strip{display:flex;gap:12px;flex-wrap:wrap;margin:24px 0}.concept{flex:1;min-width:150px;border-left:2px solid var(--line);padding:0 12px;font-size:14px;color:var(--muted)}.concept strong{display:block;color:var(--text);font-size:15px;margin-bottom:3px}.workspace{border:1px solid var(--line);border-radius:12px;overflow:hidden;background:var(--panel)}.workspace-head{display:flex;justify-content:space-between;align-items:center;gap:16px;padding:19px 22px;border-bottom:1px solid var(--line)}.eyebrow{color:var(--mint);font-size:12px;letter-spacing:1.5px}.workspace-head h2{margin:3px 0 0}.tabs{display:flex;gap:6px;flex-wrap:wrap}.tabs button{font-size:14px;padding:5px 10px}.tabs .active{background:var(--mint);border-color:var(--mint);color:var(--ink)}.lab-grid{display:grid;grid-template-columns:minmax(300px,.95fr) minmax(0,1.15fr)}.code-panel{border-right:1px solid var(--line);min-width:0;background:#0e1727}.panel-top{display:flex;align-items:center;justify-content:space-between;color:var(--muted);font-size:13px;padding:12px 18px;border-bottom:1px solid var(--line);gap:10px}.panel-top button{border:0;background:transparent;font-size:13px;padding:0;color:var(--blue)}.code-scroll{overflow:auto;max-height:435px;min-height:280px;padding:14px 0}.code-row{display:flex;border:0;border-radius:0;text-align:left;background:transparent;width:100%;min-width:max-content;padding:4px 16px 4px 10px;font:14px/1.6 ui-monospace,SFMono-Regular,Consolas,monospace;gap:15px;position:relative;color:#c9d8ee;white-space:pre}.code-row .line-num{width:24px;text-align:right;color:#8094b1;flex-shrink:0}.code-row:hover,.code-row.selected{background:#253347}.code-row.executing{background:#163e3c;box-shadow:inset 3px 0 var(--mint)}.code-row.executing .line-num{color:var(--mint)}.code-row .kw{color:#c1a6ff}.code-row .str{color:var(--amber)}.code-row .comment{color:#91a3bc}.line-detail{padding:16px 19px;background:#17253a;border-top:1px solid var(--line);min-height:126px}.line-detail span{color:var(--amber);font-size:13px}.line-detail p{font-size:14px;margin:5px 0;color:var(--text)}.visual-panel{min-width:0}.diagram-wrap{background-image:radial-gradient(#233750 1px,transparent 1px);background-size:18px 18px;padding:6px 12px}#diagram{display:block;width:100%;height:auto;max-height:305px}#diagram .edge{stroke:#4d6581;stroke-width:2;fill:none}#diagram .edge.active-edge{stroke:var(--mint);stroke-width:3}#diagram .node circle{fill:#192b43;stroke:#7d94b1;stroke-width:1.5}#diagram .node text{fill:var(--text);font-size:18px;font-weight:600;text-anchor:middle;dominant-baseline:middle;pointer-events:none}#diagram .node.current circle{fill:var(--mint);stroke:var(--mint);stroke-width:3}#diagram .node.current text{fill:var(--ink)}#diagram .node.done circle{fill:#214540;stroke:var(--mint)}#diagram .node.queued circle{stroke:var(--amber);stroke-dasharray:4 3}#diagram .node.red circle{fill:#743b48;stroke:#ff8c9c}#diagram .small-label{font-size:13px;fill:var(--muted);text-anchor:middle}#diagram .null{fill:var(--amber);font:14px ui-monospace,monospace}#diagram .node{cursor:pointer}.legend{display:flex;gap:15px;justify-content:center;font-size:12px;color:var(--muted);padding:4px 10px 11px;flex-wrap:wrap}.legend span{display:flex;align-items:center;gap:6px}.legend i{width:8px;height:8px;border-radius:50%;display:inline-block}.legend .current{background:var(--mint)}.legend .done{background:#214540;border:1px solid var(--mint)}.legend .queued{background:var(--amber)}.event-box{border-top:1px solid var(--line);padding:13px 20px;background:#142638;min-height:108px}.event-box strong{color:var(--mint);font-size:15px}.event-box p{margin:4px 0 0;font-size:14px}.runtime{padding:14px 20px;display:grid;grid-template-columns:1fr 1fr;gap:18px;border-bottom:1px solid var(--line)}#memory{display:flex;flex-wrap:wrap;gap:5px;min-height:34px}.chip{font:13px/1.6 ui-monospace,monospace;background:#203249;border-radius:4px;padding:3px 7px;white-space:nowrap}.chip.top{color:var(--mint);background:#214540}#output{display:flex;flex-wrap:wrap;gap:5px;min-height:34px}#output .chip{color:var(--amber)}.empty{font-size:13px;color:var(--muted)}.variables{font:13px/1.8 ui-monospace,monospace;color:var(--muted);padding:10px 20px;overflow-wrap:anywhere;min-height:43px}.playback{display:flex;align-items:center;gap:14px;flex-wrap:wrap;border-top:1px solid var(--line);padding:16px 20px;background:#0f192b}.play-buttons{display:flex;gap:7px;flex-wrap:wrap}.playback button{font-size:14px}.primary{background:var(--mint);color:var(--ink);border-color:var(--mint);font-weight:600}.speed{display:flex;gap:7px;align-items:center;font-size:13px;color:var(--muted)}.speed select{font-size:13px;padding:5px}.scrub-label{flex:1;min-width:160px;display:flex;gap:10px;align-items:center;font-size:13px;color:var(--muted)}input[type=range]{width:100%;accent-color:var(--mint);cursor:pointer}.lab-hint{font-size:13px;color:var(--muted);margin:0;padding:10px 20px 15px}.node-detail{padding:13px 20px;border-top:1px solid var(--line);color:var(--amber);font-size:14px}.reading-grid{display:grid;grid-template-columns:1fr 1fr;gap:20px;margin-top:25px}.reading-card{background:var(--panel);border:1px solid var(--line);border-radius:10px;padding:22px}.reading-card p{font-size:15px;color:var(--muted);margin:10px 0}.reading-card strong{color:var(--text)}.reading-card ul{padding-left:20px;color:var(--muted);font-size:15px}.wide,.quiz-card{margin-top:20px}.reading-card table{width:100%;border-collapse:collapse;font-size:14px}.table-wrap{overflow-x:auto}.reading-card th,.reading-card td{text-align:left;padding:10px 12px;border-bottom:1px solid var(--line);vertical-align:top}.reading-card th{color:var(--muted);font-weight:500}.pitfall{border-left:3px solid var(--amber);padding:9px 14px;margin-top:18px;background:#28283a;font-size:14px}.quiz-card{display:flex;justify-content:space-between;gap:18px;align-items:center;flex-wrap:wrap}.quiz-card h2{font-size:17px;margin-bottom:0}.quiz-card #answer{width:100%;margin-top:0;color:var(--mint)}footer{padding:27px 0;color:var(--muted);font-size:12px;display:flex;justify-content:space-between;gap:10px}.mono{font-family:ui-monospace,monospace}@media(min-width:1500px){main{padding-left:46px;padding-right:46px}.code-row{font-size:15px}}@media(max-width:1100px){.layout{grid-template-columns:190px minmax(0,1fr)}main{padding:25px 22px 0}aside{padding:28px 10px}.lab-grid{grid-template-columns:1fr}.code-panel{border-right:0;border-bottom:1px solid var(--line)}.code-scroll{max-height:270px;min-height:0}.line-detail{min-height:90px}.workspace-head{align-items:flex-start;flex-direction:column}#diagram{max-height:330px}.lesson-number{font-size:52px}}@media(max-width:700px){.topbar{height:72px;padding:0 16px;gap:16px}.brand{font-size:18px}.top-note{display:none}.mobile-menu{display:block;font-size:13px}.layout{display:block}aside{display:none;position:static;height:auto;border-right:0;border-bottom:1px solid var(--line)}aside.open{display:block}#course-nav{display:grid;grid-template-columns:1fr 1fr}.nav-section{grid-column:1/-1}.nav-tip{display:none}.source-link{padding:12px 14px}main{padding:22px 14px 0}h1{font-size:26px}.lesson-number{font-size:44px}.lesson-heading p{font-size:15px}.concept-strip{gap:12px;margin:20px 0}.concept{min-width:130px;flex-basis:40%;font-size:13px}.concept strong{font-size:14px}.workspace-head{padding:16px}.reading-grid{grid-template-columns:1fr;gap:16px}.reading-card{padding:18px}.runtime{gap:12px;padding:13px 16px}.playback{padding:14px;gap:13px}.play-buttons{width:100%}.play-buttons button{flex:1;padding:8px 6px;font-size:13px}.speed{width:auto}.scrub-label{min-width:130px}.code-row{font-size:13px}.legend{gap:10px;font-size:12px}.diagram-wrap{padding:8px 2px}footer{flex-direction:column}.quiz-card{align-items:flex-start}}@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important}}
#diagram .node.red.current circle{stroke:var(--mint);stroke-width:3}#diagram .node.red.current text{fill:var(--text)}
@media(max-width:700px){#diagram .node text{font-size:24px}#diagram .small-label{font-size:20px}#diagram .null{font-size:20px}}

.site-downloads{display:flex;flex-wrap:wrap;gap:8px 18px}.site-downloads a{color:var(--blue)}.site-downloads a:hover{text-decoration:underline}footer{flex-wrap:wrap}