:root{--bg:#f4f7f8;--surface:#fff;--surface2:#edf4f5;--text:#183038;--muted:#60747b;--line:#cfdcdf;--teal:#087f8c;--teal2:#11a4a4;--orange:#e56b2f;--blue:#2c6ebd;--shadow:0 18px 50px rgba(23,52,61,.10);--font:16px;--nav:245px;--paper:var(--surface);--ink:var(--text);--soft:var(--surface2);--code:#0d1d21;--course-accent:var(--teal)}
html[data-theme="dark"]{--bg:#0d171b;--surface:#152329;--surface2:#1c2d33;--text:#edf7f8;--muted:#9db1b7;--line:#31474e;--teal:#39c0c3;--teal2:#35d0c8;--orange:#ff8b55;--blue:#7bb4ff;--shadow:0 18px 50px rgba(0,0,0,.32);--code:#071113}
*{box-sizing:border-box}html{scroll-behavior:smooth;font-size:var(--font)}body{margin:0;background:var(--bg);color:var(--text);font-family:Inter,ui-sans-serif,system-ui,-apple-system,"Segoe UI",Arial,sans-serif;line-height:1.65}.reading-bar{position:fixed;z-index:1000;left:0;top:0;height:3px;width:0;background:linear-gradient(90deg,var(--orange),var(--teal2))}.topbar{position:sticky;top:0;z-index:900;height:72px;display:flex;align-items:center;justify-content:space-between;padding:0 28px;background:color-mix(in srgb,var(--surface) 92%,transparent);backdrop-filter:blur(16px);border-bottom:1px solid var(--line)}.brand{display:flex;align-items:center;gap:12px;color:var(--text);text-decoration:none}.brand-wave{display:grid;place-items:center;width:42px;height:42px;border-radius:12px;background:linear-gradient(135deg,var(--orange),var(--teal));color:#fff;font-size:28px;font-weight:800}.brand span:last-child{display:flex;flex-direction:column;line-height:1.15}.brand b{font-size:.9rem;letter-spacing:.12em}.brand small{color:var(--muted);font-size:.76rem;margin-top:4px}.top-actions{display:flex;align-items:center;gap:8px}.top-btn,.font-box,.menu-btn{height:38px;border:1px solid var(--line);background:var(--surface);color:var(--text);border-radius:10px}.top-btn{padding:0 13px;cursor:pointer}.font-box{display:flex;align-items:center;overflow:hidden}.font-box button{border:0;background:transparent;color:var(--text);height:100%;padding:0 10px;cursor:pointer}.font-box span{min-width:30px;text-align:center;color:var(--muted)}.menu-btn{display:none;width:40px;font-size:20px}.page-shell{display:grid;grid-template-columns:var(--nav) minmax(0,1fr);max-width:1500px;margin:auto}.side-nav{position:sticky;top:72px;height:calc(100vh - 72px);padding:28px 20px;border-right:1px solid var(--line);overflow:auto}.nav-head{font-size:.72rem;letter-spacing:.18em;color:var(--muted);font-weight:800;margin-bottom:14px}.side-nav nav{display:flex;flex-direction:column;gap:3px}.side-nav nav a{padding:8px 11px;border-radius:9px;color:var(--muted);text-decoration:none;font-size:.88rem;border-left:3px solid transparent}.side-nav nav a:hover,.side-nav nav a.active{background:var(--surface2);color:var(--text);border-left-color:var(--teal)}.nav-note{margin-top:20px;padding:12px;border-radius:10px;background:var(--surface2);font-size:.78rem;color:var(--muted)}main{min-width:0;padding:0 38px 90px}.lesson-section{scroll-margin-top:92px;max-width:1150px;margin:0 auto;padding:88px 0;border-bottom:1px solid var(--line)}.hero{min-height:calc(100vh - 72px);display:grid;grid-template-columns:1.1fr .9fr;align-items:center;gap:55px}.kicker{font-size:.76rem;letter-spacing:.2em;color:var(--teal);font-weight:900}.hero h1{font-size:clamp(2.5rem,5vw,5.2rem);line-height:1.04;letter-spacing:-.055em;margin:18px 0 24px;max-width:800px}.lead{font-size:1.16rem;color:var(--muted);max-width:680px}.hero-actions{display:flex;gap:12px;margin-top:28px}.primary-link,.secondary-link{display:inline-flex;align-items:center;justify-content:center;padding:11px 18px;border-radius:11px;text-decoration:none;font-weight:750;cursor:pointer}.primary-link{background:var(--teal);color:#fff;border:1px solid var(--teal)}.secondary-link{background:var(--surface);color:var(--text);border:1px solid var(--line)}.hover-reminder{display:inline-flex;align-items:center;gap:8px;margin-top:26px;color:var(--muted);font-size:.86rem}.hover-reminder span{display:grid;place-items:center;width:28px;height:28px;border-radius:50%;background:var(--orange);color:#fff;font-weight:800}.hero-visual{height:480px;position:relative;border-radius:30px;background:radial-gradient(circle at 70% 10%,color-mix(in srgb,var(--teal2) 28%,transparent),transparent 45%),linear-gradient(150deg,var(--surface),var(--surface2));border:1px solid var(--line);box-shadow:var(--shadow);overflow:hidden}.hero-graph{position:absolute;width:92%;left:4%;bottom:22px}.graph-grid{fill:none;stroke:var(--line);stroke-width:1}.graph-area{fill:url(#area)}.graph-line{fill:none;stroke:var(--teal2);stroke-width:5;stroke-linecap:round;stroke-dasharray:900;animation:draw 2.5s ease both}.calc-card,.matrix-card{position:absolute;z-index:2;background:var(--surface);border:1px solid var(--line);box-shadow:var(--shadow)}.calc-card{right:24px;top:24px;width:150px;border-radius:18px;padding:18px}.calc-card span{display:block;color:var(--muted)}.calc-card b{display:block;font-size:2.4rem;color:var(--orange)}.matrix-card{left:28px;top:60px;display:grid;grid-template-columns:repeat(2,45px);padding:16px;border-radius:17px}.matrix-card i{display:grid;place-items:center;height:42px;font-style:normal;border:1px solid var(--line)}.float-a{animation:float 4s ease-in-out infinite}.float-b{animation:float 4.8s ease-in-out infinite reverse}.section-head{display:flex;gap:18px;align-items:flex-start;margin-bottom:34px}.section-head>span{display:grid;place-items:center;min-width:50px;height:50px;border-radius:14px;background:var(--surface2);color:var(--teal);font-weight:900}.section-head h2{font-size:clamp(2rem,4vw,3.5rem);letter-spacing:-.04em;line-height:1.05;margin:0}.section-head p{margin:9px 0 0;color:var(--muted);font-size:1.04rem}.concept-grid{display:grid;gap:16px}.concept-grid.four{grid-template-columns:repeat(4,1fr)}.concept-card{padding:24px;border:1px solid var(--line);border-radius:18px;background:var(--surface);transition:.25s}.concept-card:hover{transform:translateY(-5px);box-shadow:var(--shadow)}.concept-card .icon{display:grid;place-items:center;width:44px;height:44px;border-radius:13px;background:var(--surface2);color:var(--teal);font-size:22px}.concept-card h3{margin:18px 0 8px}.concept-card p{margin:0;color:var(--muted);font-size:.92rem}.story-strip{display:flex;align-items:center;justify-content:center;gap:18px;margin:35px 0 20px;padding:25px;border-radius:18px;background:var(--surface2)}.story-word{font-size:2.4rem;font-weight:900;color:var(--orange)}.story-arrow,.story-equals{font-size:1.7rem;color:var(--muted)}.story-result{font-size:1.35rem}.plain{font-size:1.08rem;color:var(--muted);max-width:940px}.mode-compare{display:grid;grid-template-columns:1fr auto 1fr;align-items:center;gap:18px}.mode-card{position:relative;min-height:310px;padding:28px;border-radius:22px;background:var(--surface);border:1px solid var(--line);box-shadow:var(--shadow)}.window-dots{display:flex;gap:6px}.window-dots i{width:10px;height:10px;border-radius:50%;background:var(--line)}.window-dots i:first-child{background:#f06b60}.window-dots i:nth-child(2){background:#f1bd4a}.window-dots i:nth-child(3){background:#61c46d}.mode-card h3{font-size:1.4rem}.mini-terminal,.mode-card pre{height:125px;padding:18px;border-radius:13px;background:#101a1e;color:#d7f8f3;font:600 .95rem/1.8 ui-monospace,Consolas,monospace}.mini-terminal span,.mini-terminal b{display:block}.mini-terminal b{color:#8fe1d5}.cursor{display:inline-block!important;width:9px;height:17px;background:#fff;animation:blink 1s step-end infinite}.mode-card p{color:var(--muted)}.or-badge{font-size:.75rem;font-weight:900;color:var(--muted)}.analogy,.warning,.symbolic-note{margin-top:22px;padding:17px 20px;border-radius:14px;background:var(--surface2);border-left:4px solid var(--orange)}.desktop-demo{display:grid;grid-template-columns:1fr 1fr 1.7fr;grid-template-rows:40px 180px 180px 88px;gap:8px;padding:12px;border:1px solid var(--line);border-radius:18px;background:var(--surface);box-shadow:var(--shadow)}.desktop-toolbar{grid-column:1/-1;display:flex;gap:30px;align-items:center;padding:0 16px;background:#0c6a85;color:#fff;border-radius:9px}.desk-panel{border:1px solid var(--line);background:var(--surface2);color:var(--text);border-radius:10px;padding:14px;text-align:left;cursor:pointer;transition:.2s}.desk-panel:hover,.desk-panel.active{outline:3px solid color-mix(in srgb,var(--teal) 25%,transparent);border-color:var(--teal)}.desk-panel b{display:block;margin-bottom:10px}.desk-panel small{color:var(--muted);font-family:ui-monospace,monospace}.folder{grid-row:2}.workspace{grid-row:3;grid-column:1}.history{grid-row:2/4;grid-column:2}.command{grid-row:2/4;grid-column:3}.desktop-explain{grid-column:1/-1;display:flex;align-items:center;padding:0 18px;background:var(--surface2);border-radius:10px}.note-row{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin-top:18px}.note-row p{margin:0;padding:16px;border:1px solid var(--line);border-radius:13px;color:var(--muted)}.operator-ribbon{display:grid;grid-template-columns:repeat(5,1fr);gap:10px}.operator-ribbon span{display:flex;flex-direction:column;align-items:center;padding:15px;border-radius:14px;background:var(--surface);border:1px solid var(--line);font-size:.82rem;color:var(--muted)}.operator-ribbon b{font-size:1.8rem;color:var(--teal)}.precedence-card{display:grid;grid-template-columns:.8fr 1.2fr;gap:25px;margin-top:20px;padding:24px;border-radius:18px;background:var(--surface2)}.precedence-card h3{margin-top:0}.precedence-card p{color:var(--muted)}.precedence-steps{display:flex;flex-direction:column;gap:7px}.precedence-steps button{padding:10px 13px;border:1px solid var(--line);background:var(--surface);color:var(--text);text-align:left;border-radius:9px;font-family:ui-monospace,monospace;cursor:pointer}.precedence-steps button.active{border-color:var(--orange);background:color-mix(in srgb,var(--orange) 9%,var(--surface))}.characters-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:12px;margin-top:20px}.characters-grid article{padding:20px;border-radius:15px;border:1px solid var(--line);background:var(--surface)}.characters-grid code{font-size:2rem;color:var(--orange)}.characters-grid p{color:var(--muted);font-size:.88rem}.lab-intro{margin:26px 0 10px;color:var(--muted)}.variable-machine{display:flex;gap:30px;align-items:center;justify-content:center;padding:34px;background:var(--surface2);border-radius:18px}.assignment{display:flex;align-items:center;gap:11px}.assignment.result{padding-left:25px;border-left:1px solid var(--line)}.name-box,.value-box{display:grid;place-items:center;min-width:65px;min-height:58px;border-radius:12px;background:var(--surface);border:1px solid var(--line);font:800 1.25rem ui-monospace,monospace}.name-box{color:var(--teal)}.value-box{color:var(--orange);padding:0 14px}.arrow{color:var(--muted)}.command-table{display:grid;grid-template-columns:repeat(5,1fr);gap:10px;margin-top:22px}.command-table>div{padding:15px;border:1px solid var(--line);border-radius:13px;background:var(--surface)}.command-table code{display:block;color:var(--teal);font-weight:800;margin-bottom:8px}.command-table span{font-size:.8rem;color:var(--muted)}.function-machine-demo{display:flex;align-items:center;justify-content:center;gap:25px;padding:30px;border-radius:18px;background:var(--surface2)}.fn-input,.fn-output{display:grid;place-items:center;width:90px;height:70px;border-radius:15px;background:var(--surface);border:1px solid var(--line);font-size:1.4rem;font-weight:800}.fn-machine{display:grid;place-items:center;width:190px;height:100px;border-radius:50px;background:linear-gradient(135deg,var(--teal),var(--teal2));color:#fff;font:800 1.2rem ui-monospace,monospace}.function-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:10px;margin-top:18px}.function-grid>div{display:flex;justify-content:space-between;gap:8px;padding:13px 16px;border:1px solid var(--line);border-radius:11px;background:var(--surface)}.function-grid span{color:var(--muted)}.function-command-compare{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin-top:18px}.function-command-compare>div{padding:19px;border:1px solid var(--line);border-radius:15px;background:var(--surface)}.function-command-compare h3{margin-top:0;font-size:1rem}.function-command-compare code{display:inline-block;margin:4px;padding:5px 8px;border-radius:7px;background:var(--surface2)}.array-levels{display:grid;grid-template-columns:repeat(3,1fr);gap:18px}.array-levels article{text-align:center;padding:25px;border-radius:18px;background:var(--surface);border:1px solid var(--line)}.candy{margin:0 auto;min-height:85px;display:grid;place-items:center}.candy.one{width:70px;border-radius:16px;background:var(--orange);color:#fff;font-size:1.5rem}.candy.row{grid-template-columns:repeat(4,50px);justify-content:center;align-content:center}.candy.grid{grid-template-columns:repeat(3,50px);justify-content:center;align-content:center}.candy i{display:grid;place-items:center;width:50px;height:50px;background:var(--surface2);border:1px solid var(--line);border-radius:6px;font-style:normal}.array-levels p{color:var(--muted)}.vector-builder{margin-top:20px;padding:22px;border:1px solid var(--line);border-radius:18px;background:var(--surface)}.vector-builder>div:first-child{display:flex;gap:14px;flex-wrap:wrap}.vector-builder label{display:flex;align-items:center;gap:8px;color:var(--muted)}.vector-builder input{width:78px;padding:7px;border:1px solid var(--line);border-radius:8px;background:var(--bg);color:var(--text)}.colon-code{margin:18px 0;font:800 1.25rem ui-monospace,monospace;color:var(--teal)}.vector-tiles{display:flex;flex-wrap:wrap;gap:5px}.vector-tiles i{display:grid;place-items:center;min-width:41px;height:41px;padding:0 6px;border:1px solid var(--line);background:var(--surface2);font-style:normal;border-radius:7px;animation:pop .25s ease both}.nan-demo{display:grid;grid-template-columns:auto auto 1fr;align-items:center;gap:18px;margin-top:20px;padding:18px;border-radius:15px;background:var(--surface2)}.nan-demo>div{display:flex;align-items:center;gap:8px}.nan-demo b{color:var(--orange)}.plot-explainer{display:grid;grid-template-columns:.65fr 1.35fr;gap:25px;align-items:center;padding:20px;border-radius:18px;background:var(--surface)}.point-table{border:1px solid var(--line);border-radius:13px;overflow:hidden}.point-table>div{display:grid;grid-template-columns:1fr repeat(3,1fr)}.point-table span,.point-table b{padding:10px;text-align:center;border-right:1px solid var(--line);border-bottom:1px solid var(--line)}.point-table b{background:var(--surface2)}.plot-explainer svg{width:100%;height:300px}.axis{fill:none;stroke:var(--line);stroke-width:1.5}.plot-path{fill:none;stroke:var(--teal);stroke-width:4}.plot-explainer circle{fill:var(--orange)}.plot-explainer text{fill:var(--text);font-size:14px}.plot-explainer input{grid-column:2;width:100%}.style-chips{display:flex;flex-wrap:wrap;gap:8px;margin-top:16px}.style-chips span{padding:7px 11px;border:1px solid var(--line);border-radius:999px;background:var(--surface);font-size:.83rem}.style-chips b{color:var(--orange)}.matrix-shape-demo{display:grid;grid-template-columns:1fr 1fr;gap:40px;align-items:center;padding:28px;border-radius:18px;background:var(--surface2)}.matrix-bracket{position:relative;display:grid;place-items:center;padding:20px}.matrix-bracket:before,.matrix-bracket:after{content:"";position:absolute;top:5%;height:90%;width:18px;border:4px solid var(--text)}.matrix-bracket:before{left:20%;border-right:0}.matrix-bracket:after{right:20%;border-left:0}.matrix-3x3{display:grid;grid-template-columns:repeat(3,65px)}.matrix-3x3 i{display:grid;place-items:center;height:58px;font-style:normal;font-size:1.15rem;border-radius:8px;transition:.2s}.matrix-3x3 i.hi{background:var(--orange);color:#fff}.shape-controls{display:flex;flex-wrap:wrap;gap:8px}.shape-controls button{padding:8px 11px;border:1px solid var(--line);background:var(--surface);color:var(--text);border-radius:9px;cursor:pointer}.shape-controls button.active{background:var(--teal);color:#fff}.shape-controls p{width:100%;color:var(--muted)}.matrix-rule-grid{display:grid;grid-template-columns:1fr 1fr;gap:15px;margin-top:18px}.matrix-rule-grid article{padding:20px;border-radius:15px;border:1px solid var(--line);background:var(--surface)}.matrix-rule-grid p{color:var(--muted)}.mini-matrix-sum{display:flex;align-items:center;justify-content:center;gap:14px;font:700 1rem/1.6 ui-monospace,monospace;color:var(--teal)}.multiply-demo{display:grid;grid-template-columns:auto auto auto auto auto;align-items:center;justify-content:center;gap:18px;margin-top:18px;padding:28px;border-radius:18px;background:var(--surface2)}.matrix2{display:grid;grid-template-columns:repeat(2,55px)}.matrix2 i{display:grid;place-items:center;height:55px;font-style:normal;border-radius:7px;transition:.2s}.matrix2 i.hi{background:var(--teal);color:#fff}.matrix2.answer i.hi{background:var(--orange)}.mul-sign{font-size:1.5rem}.multiply-control{grid-column:1/-1;text-align:center;width:min(600px,100%)}.multiply-control input{width:100%}.multiply-control div{font:800 1.2rem ui-monospace,monospace;color:var(--orange)}.multiply-control p{color:var(--muted)}.left-division-card{display:flex;align-items:center;justify-content:center;gap:22px;flex-wrap:wrap;margin-top:18px;padding:20px;border:1px solid var(--line);border-radius:15px;background:var(--surface)}.left-division-card .equation{font:800 1.35rem ui-monospace,monospace;color:var(--teal)}.left-division-card p{width:100%;text-align:center;color:var(--muted);margin:0}.equation-visual{display:grid;grid-template-columns:.7fr 1.3fr;gap:22px;align-items:center}.equation-list>div{padding:13px 16px;margin:8px 0;border-radius:11px;background:var(--surface);border:1px solid var(--line);font:700 1.1rem ui-monospace,monospace}.equation-list .solution{border-color:var(--orange);color:var(--orange)}.equation-visual svg{width:100%;max-height:340px;background:var(--surface);border:1px solid var(--line);border-radius:16px}.line-one{stroke:var(--teal);stroke-width:4}.line-two{stroke:var(--orange);stroke-width:4}.equation-visual circle{fill:var(--blue)}.equation-visual text{fill:var(--text)}.equation-to-matrix{display:flex;align-items:center;justify-content:center;gap:18px;padding:20px;margin-top:17px;border-radius:15px;background:var(--surface2);font:800 1.1rem ui-monospace,monospace}.script-flow,.summary-path{display:flex;align-items:stretch;justify-content:center;gap:10px;flex-wrap:wrap}.script-flow>div,.summary-path>div{display:flex;align-items:center;gap:10px;padding:14px;border-radius:13px;background:var(--surface);border:1px solid var(--line)}.script-flow b,.summary-path b{display:grid;place-items:center;width:29px;height:29px;border-radius:50%;background:var(--teal);color:#fff}.script-flow i,.summary-path i{display:grid;place-items:center;color:var(--muted);font-style:normal}.filename-rules{margin-top:22px;padding:22px;border-radius:18px;background:var(--surface2)}.filename-rules h3{margin-top:0}.rule{display:grid;grid-template-columns:200px 1fr;gap:18px;padding:11px 0;border-top:1px solid var(--line)}.rule code{font-weight:800}.rule.good code{color:var(--teal)}.rule.bad code{color:var(--orange)}.cone-visual{display:grid;grid-template-columns:.55fr 1.45fr;gap:30px;align-items:center;margin-top:20px;padding:20px;border:1px solid var(--line);border-radius:18px;background:var(--surface)}.cone-visual svg{width:100%;height:220px}.cone-visual ellipse,.cone-visual path{fill:none;stroke:var(--teal);stroke-width:3}.cone-visual .measure{stroke:var(--orange);stroke-dasharray:5 5}.cone-visual text{fill:var(--text);font-size:18px}.formula{font:900 2rem ui-monospace,monospace;color:var(--orange)}.help-box{border:1px solid var(--line);border-radius:18px;overflow:hidden;background:#0f1a1e;color:#d9f8f4;box-shadow:var(--shadow)}.help-search{display:flex;align-items:center;gap:12px;padding:14px 18px;border-bottom:1px solid #2e4147}.help-search code{flex:1}.help-search button{border:1px solid #4f6870;background:#203239;color:#fff;border-radius:8px;padding:7px 11px;cursor:pointer}.help-box>div:last-child{padding:23px;font-family:ui-monospace,monospace;color:#95e1d7}.help-options{display:flex;flex-wrap:wrap;gap:8px;margin:16px 0 25px}.help-options code{padding:8px 11px;border-radius:8px;background:var(--surface2)}.finish-card{margin-top:30px;padding:32px;border-radius:22px;background:linear-gradient(135deg,color-mix(in srgb,var(--teal) 16%,var(--surface)),var(--surface));border:1px solid var(--line);text-align:center}.finish-card h3{font-size:1.6rem;margin-top:0}.finish-card p{max-width:760px;margin:0 auto 22px;color:var(--muted)}
/* labs */.matlab-lab{margin-top:20px;border:1px solid var(--line);border-radius:18px;background:var(--surface);box-shadow:var(--shadow);overflow:hidden}.lab-header{display:flex;align-items:center;justify-content:space-between;padding:11px 14px;background:linear-gradient(90deg,#0a6f88,#0e8795);color:#fff}.lab-header h3{font-size:.92rem;margin:0}.lab-header small{opacity:.8}.lab-actions{display:flex;gap:7px}.lab-actions button{border:1px solid rgba(255,255,255,.35);background:rgba(255,255,255,.12);color:#fff;border-radius:8px;padding:6px 10px;cursor:pointer}.lab-body{display:flex;height:390px;min-height:280px}.lab-pane{min-width:180px;overflow:hidden}.lab-code-pane{flex:0 0 48%;display:flex;flex-direction:column;background:#111c20}.lab-result-pane{flex:1;display:flex;flex-direction:column;background:var(--surface)}.lab-splitter{flex:0 0 8px;cursor:col-resize;background:var(--line);position:relative}.lab-splitter:after{content:"";position:absolute;width:2px;height:45px;background:var(--muted);left:3px;top:calc(50% - 22px);opacity:.45}.lab-pane-title{height:36px;display:flex;align-items:center;justify-content:space-between;padding:0 12px;font-size:.74rem;letter-spacing:.08em;text-transform:uppercase;border-bottom:1px solid var(--line)}.lab-code-pane .lab-pane-title{color:#9ac8cf;border-color:#2d4147}.lab-mode-badge{padding:2px 7px;border-radius:999px;background:rgba(255,255,255,.09)}.lab-editor-wrap{display:flex;flex:1;min-height:0}.lab-prompt{padding:14px 0 0 12px;color:#62d7c8;font:700 .9rem ui-monospace,monospace}.lab-editor{flex:1;width:100%;border:0;outline:0;resize:none;background:#111c20;color:#e6f3f4;padding:14px;font:500 .9rem/1.65 ui-monospace,SFMono-Regular,Consolas,monospace;tab-size:4}.lab-output{flex:0 0 47%;margin:0;padding:14px;overflow:auto;white-space:pre-wrap;color:var(--text);font:500 .85rem/1.55 ui-monospace,Consolas,monospace;border-bottom:1px solid var(--line)}.lab-figures{flex:1;overflow:auto;padding:8px;min-height:100px}.lab-figures:empty:before{content:"Figure output will appear here when the code creates a plot.";display:grid;place-items:center;height:100%;color:var(--muted);font-size:.82rem;text-align:center;padding:15px}.lab-workspace{display:flex;gap:6px;flex-wrap:wrap;padding:7px 10px;border-top:1px solid var(--line);min-height:34px}.lab-workspace span{padding:3px 7px;border-radius:6px;background:var(--surface2);font:600 .72rem ui-monospace,monospace}.figure-card{border:1px solid var(--line);border-radius:10px;overflow:hidden;background:#fff}.figure-card header{display:flex;justify-content:space-between;padding:5px 8px;background:#eef2f4;color:#33464c;font-size:11px}.figure-card canvas{display:block;max-width:100%;height:auto!important}.lab-status.error{color:#d94841}.lab-status.ok{color:#91f0d7}
.tooltip{position:fixed;z-index:2000;display:none;max-width:360px;padding:9px 12px;border-radius:9px;background:#162429;color:#fff;box-shadow:0 12px 36px rgba(0,0,0,.28);font-size:13px;line-height:1.5;pointer-events:none}.tips-off [data-zh]{text-decoration:none!important;cursor:default!important}[data-zh]{cursor:help}[data-zh]:hover{text-decoration:underline;text-decoration-style:dotted;text-decoration-color:color-mix(in srgb,var(--teal) 55%,transparent);text-underline-offset:3px}.tour-overlay{position:fixed;z-index:1800;inset:0;display:none;place-items:center;background:rgba(8,18,22,.72);backdrop-filter:blur(8px)}.tour-overlay.open{display:grid}.tour-card{position:relative;width:min(560px,calc(100% - 30px));padding:34px;border-radius:22px;background:var(--surface);box-shadow:0 30px 90px rgba(0,0,0,.35)}.tour-card>button:first-child{position:absolute;right:15px;top:12px;border:0;background:transparent;color:var(--text);font-size:24px;cursor:pointer}.tour-card h2{font-size:2rem}.tour-card p{color:var(--muted)}#tourCount{color:var(--teal);font-weight:800}#tourNext{padding:10px 16px;border:0;border-radius:10px;background:var(--teal);color:#fff;cursor:pointer}
@keyframes draw{from{stroke-dashoffset:900}to{stroke-dashoffset:0}}@keyframes float{50%{transform:translateY(-12px)}}@keyframes blink{50%{opacity:0}}@keyframes pop{from{transform:scale(.75);opacity:0}to{transform:scale(1);opacity:1}}
@media(max-width:1050px){:root{--nav:210px}.concept-grid.four{grid-template-columns:repeat(2,1fr)}.hero{grid-template-columns:1fr}.hero-visual{height:380px}.command-table{grid-template-columns:repeat(3,1fr)}.characters-grid{grid-template-columns:repeat(2,1fr)}.multiply-demo{gap:8px}.matrix2{grid-template-columns:repeat(2,48px)}.matrix2 i{height:48px}}
@media(max-width:780px){.topbar{padding:0 14px}.brand small,.top-actions>.top-btn,.font-box{display:none}.menu-btn{display:block}.page-shell{display:block}.side-nav{position:fixed;z-index:850;left:-270px;top:72px;width:260px;background:var(--surface);transition:.25s}.side-nav.open{left:0;box-shadow:20px 0 50px rgba(0,0,0,.25)}main{padding:0 18px 70px}.lesson-section{padding:68px 0}.hero{padding-top:35px}.hero h1{font-size:2.75rem}.concept-grid.four,.array-levels,.matrix-rule-grid,.function-grid,.function-command-compare,.note-row,.precedence-card,.matrix-shape-demo,.equation-visual,.cone-visual,.plot-explainer{grid-template-columns:1fr}.mode-compare{grid-template-columns:1fr}.or-badge{text-align:center}.operator-ribbon{grid-template-columns:repeat(5,1fr)}.operator-ribbon span{padding:8px 3px}.command-table{grid-template-columns:1fr 1fr}.desktop-demo{grid-template-columns:1fr 1fr;grid-template-rows:40px 140px 140px 160px 86px}.folder{grid-row:2;grid-column:1}.workspace{grid-row:2;grid-column:2}.history{grid-row:3;grid-column:1}.command{grid-row:3/5;grid-column:2}.desktop-explain{grid-row:5}.plot-explainer input{grid-column:1}.multiply-demo{overflow:auto;justify-content:flex-start}.lab-body{height:520px;flex-direction:column}.lab-code-pane{flex:0 0 48%!important}.lab-splitter{flex:0 0 8px;cursor:row-resize}.lab-splitter:after{width:45px;height:2px;left:calc(50% - 22px);top:3px}.lab-result-pane{min-height:0}.variable-machine{flex-direction:column}.assignment.result{border-left:0;border-top:1px solid var(--line);padding-left:0;padding-top:20px}.story-strip{gap:8px;flex-wrap:wrap}.story-word{font-size:1.8rem}.rule{grid-template-columns:1fr}.summary-path i,.script-flow i{display:none}}
.output-methods{margin-top:18px;padding:20px;border:1px solid var(--line);border-radius:16px;background:var(--surface2)}.output-methods h3{margin:0 0 12px}.output-methods>div{display:grid;grid-template-columns:180px 1fr;gap:15px;padding:10px 0;border-top:1px solid var(--line)}.output-methods>div code{color:var(--teal);font-weight:800}.output-methods>div span{color:var(--muted)}.style-reference,.symbolic-route{margin-top:14px;border:1px solid var(--line);border-radius:13px;background:var(--surface);overflow:hidden}.style-reference summary,.symbolic-route summary{padding:12px 15px;cursor:pointer;font-weight:750}.style-reference>div{display:flex;align-items:center;flex-wrap:wrap;gap:7px;padding:10px 15px;border-top:1px solid var(--line)}.style-reference b{width:72px}.style-reference code{padding:4px 7px;border-radius:6px;background:var(--surface2);font-size:.78rem}.symbolic-route pre{margin:0;padding:17px;border-top:1px solid var(--line);background:#101a1e;color:#d8f5f1;overflow:auto}.lab-figures.no-figure{display:none}.lab-result-pane.no-figure .lab-output{flex:1;border-bottom:0}@media(max-width:780px){.output-methods>div{grid-template-columns:1fr}}

/* v3.1 bilingual presentation and reusable expanded runtime */
body.lang-zh{font-family:"Microsoft YaHei","PingFang SC","Noto Sans CJK SC",Inter,ui-sans-serif,system-ui,sans-serif}
body.resizing{user-select:none;cursor:col-resize}
[hidden]{display:none!important}
#langBtn{font-weight:800;min-width:66px;color:var(--teal)}
.lab-header{gap:14px;flex-wrap:wrap}
.lab-actions{flex-wrap:wrap;justify-content:flex-end}
.lab-actions button{white-space:nowrap;transition:.18s transform,.18s background,.18s opacity}
.lab-actions button:hover:not(:disabled){transform:translateY(-1px);background:rgba(255,255,255,.22)}
.lab-actions button:disabled{opacity:.45;cursor:not-allowed}
.lab-run{background:rgba(255,255,255,.26)!important;font-weight:800}
.lab-body{height:340px;min-height:270px}
.lab-output{flex:1;border-bottom:0;min-height:0;padding:18px;font-size:.9rem}
.lab-output:empty:before{content:""}
.lab-workspace{min-height:42px;max-height:92px;overflow:auto}
.lab-extension{border-top:1px solid var(--line);background:var(--surface2);padding:14px}
.lab-extension-head{display:flex;align-items:center;justify-content:space-between;gap:18px;margin-bottom:12px;padding:2px 4px}
.lab-extension-head>div{display:flex;flex-direction:column}
.lab-extension-head b{font-size:1rem}
.lab-extension-head small{color:var(--muted)}
.lab-extension-head button{border:1px solid var(--line);background:var(--surface);color:var(--text);border-radius:9px;padding:7px 11px;cursor:pointer}
.lab-large-figures{display:grid;gap:14px;width:100%;overflow:auto}
.lab-large-figures:empty{display:none}
.lab-large-figures .figure-card{width:100%;border-radius:14px;box-shadow:0 10px 28px rgba(22,49,58,.08)}
.lab-large-figures .figure-card header{padding:8px 12px;font-size:.78rem}
.lab-large-figures .figure-card canvas{width:100%!important;max-width:none;height:auto!important}
.lab-extension.has-figure{padding-bottom:20px}
.lab-extension.has-figure .lab-large-figures{min-height:420px}
.lab-editor{caret-color:#6ff1dd}
.lab-editor:focus{box-shadow:inset 0 0 0 2px rgba(57,192,195,.16)}
.lab-status{font-weight:700}
html[data-theme="dark"] .lab-large-figures .figure-card{border-color:#41555c}

@media(max-width:960px){
  .topbar{height:auto;min-height:72px;padding-block:10px}
  .top-actions{flex-wrap:wrap;justify-content:flex-end}
  .lab-actions{width:100%;justify-content:flex-start}
  .lab-header>div:first-child{flex:1 1 260px}
}
@media(max-width:780px){
  .top-actions>.top-btn{display:inline-flex;align-items:center}
  #tipToggle,#themeBtn{display:none}
  .lab-body{height:590px}
  .lab-extension{padding:10px}
  .lab-extension.has-figure .lab-large-figures{min-height:300px}
  body.resizing{cursor:row-resize}
}
@media(max-width:520px){
  .brand b{font-size:.72rem}.brand-wave{width:36px;height:36px}
  .lab-actions button{padding:6px 8px;font-size:.72rem}
  .lab-header{padding:10px}
}

/* v3.2 refinements */
.hero h1{max-width:650px}
.matrix-basics{display:grid;grid-template-columns:repeat(3,1fr);gap:14px;margin:18px 0 22px}
.matrix-basics article{padding:18px;border:1px solid var(--line);border-radius:15px;background:var(--surface)}
.matrix-basics b{display:block;margin-bottom:8px;color:var(--teal);font:800 1.15rem ui-monospace,Consolas,monospace}
.matrix-basics p{margin:0;color:var(--muted)}
.matrix-equation-three{display:flex;align-items:center;justify-content:center;gap:10px;overflow:auto;padding:10px 0}
.matrix3-static,.matrix3op{display:grid;grid-template-columns:repeat(3,42px);gap:3px;padding:8px;border-left:3px solid var(--text);border-right:3px solid var(--text);border-radius:5px;background:var(--surface2)}
.matrix3-static i,.matrix3op i{display:grid;place-items:center;height:38px;font-style:normal;border-radius:6px;transition:.2s;background:var(--surface)}
.matrix3-static.answer i{color:var(--orange);font-weight:800}
.matrix-steps{margin:10px 0 0;padding-left:1.25rem;color:var(--muted)}
.matrix-steps li{margin:7px 0}
.multiply-demo-3{display:grid;grid-template-columns:auto auto auto auto auto;align-items:center;justify-content:center;gap:14px}
.multiply-demo-3>div:not(.mul-sign):not(.multiply-control){text-align:center}
.matrix-label{display:block;margin-bottom:7px;font-weight:900;color:var(--muted)}
.matrix3op i.hi{background:var(--teal);color:#fff;transform:scale(1.04)}
.matrix3op.answer i.hi{background:var(--orange)}
.multiply-demo-3 .multiply-control{grid-column:1/-1;margin-top:8px}
.multiply-control label{display:block;margin-bottom:9px;color:var(--muted)}
.equation-steps{display:grid;gap:14px;margin-top:24px}
.equation-steps article{display:grid;grid-template-columns:46px 1fr;gap:16px;padding:20px;border:1px solid var(--line);border-radius:16px;background:var(--surface)}
.equation-steps article>span{display:grid;place-items:center;width:42px;height:42px;border-radius:13px;background:var(--teal);color:#fff;font-weight:900}
.equation-steps h3{margin:0 0 8px}
.equation-steps p{margin:0;color:var(--muted)}
.equation-to-matrix.detailed{justify-content:flex-start;flex-wrap:wrap;margin:8px 0 10px;padding:0;background:transparent}
.equation-to-matrix.detailed span{padding:9px 12px;border-radius:9px;background:var(--surface2)}
.equation-code{display:inline-block;padding:10px 14px;border-radius:10px;background:#101a1e;color:#9ff0e6;font:800 1rem ui-monospace,Consolas,monospace}
.check-grid{display:flex;flex-wrap:wrap;gap:10px;margin-bottom:9px}
.check-grid code{padding:8px 11px;border-radius:9px;background:var(--surface2);color:var(--orange);font-weight:800}
.figure-card{transition:border-color .18s,box-shadow .18s,transform .18s}
.figure-card canvas{touch-action:none;user-select:none}
.figure-card.plot-selected{border:2px solid var(--teal2)!important;box-shadow:0 0 0 4px color-mix(in srgb,var(--teal2) 22%,transparent),0 18px 42px rgba(14,85,92,.18);transform:translateY(-1px)}
.figure-card.plot-selected header{background:color-mix(in srgb,var(--teal2) 14%,#eef2f4);font-weight:800}
.figure-card.plot-selected canvas{cursor:grab}
.figure-card.plot-selected canvas.is-panning{cursor:grabbing}
html[data-theme="dark"] .figure-card.plot-selected header{background:color-mix(in srgb,var(--teal2) 18%,#24343a);color:#eafafa}

@media(max-width:900px){
  .matrix-basics{grid-template-columns:1fr}
  .multiply-demo-3{grid-template-columns:1fr;justify-items:center}
  .multiply-demo-3 .mul-sign{transform:rotate(90deg)}
  .multiply-demo-3 .multiply-control{grid-column:1}
}
@media(max-width:620px){
  .matrix-equation-three{justify-content:flex-start}
  .matrix3-static,.matrix3op{grid-template-columns:repeat(3,36px)}
  .matrix3-static i,.matrix3op i{height:34px;font-size:.82rem}
  .equation-steps article{grid-template-columns:1fr}
}


/* v3.3 original lecture slide viewer */
.section-head>div{flex:1;min-width:0}
.source-slide-btn{display:inline-flex;align-items:center;justify-content:center;gap:7px;flex:0 0 auto;margin-left:auto;min-height:38px;padding:8px 12px;border:1px solid var(--line);border-radius:11px;background:var(--surface);color:var(--text);font:750 .78rem/1.1 Inter,ui-sans-serif,system-ui,sans-serif;cursor:pointer;box-shadow:0 5px 15px rgba(22,49,58,.05);transition:.18s transform,.18s border-color,.18s background,.18s box-shadow}
.source-slide-btn:hover{transform:translateY(-2px);border-color:var(--teal);background:color-mix(in srgb,var(--teal) 7%,var(--surface));box-shadow:0 10px 24px rgba(22,49,58,.1)}
.source-slide-btn>span:first-child{display:grid;place-items:center;width:23px;height:23px;border-radius:7px;background:color-mix(in srgb,var(--teal) 13%,var(--surface2));color:var(--teal);font-size:.9rem}
.source-slide-btn small{padding-left:7px;border-left:1px solid var(--line);color:var(--muted);font-size:.69rem;font-weight:700}
.hero-actions{flex-wrap:wrap}
.hero-actions .source-slide-btn{margin-left:0;padding:11px 15px;font-size:.82rem}
body.source-slides-open{overflow:hidden}
.source-slides-overlay{position:fixed;inset:0;z-index:1600;display:none;place-items:center;padding:20px;background:rgba(3,12,15,.92);backdrop-filter:blur(12px);opacity:0;transition:opacity .2s ease}
.source-slides-overlay.open{display:grid;opacity:1}
.source-slides-dialog{position:relative;display:flex;flex-direction:column;width:min(1420px,96vw);height:min(920px,94vh);padding:22px;border:1px solid rgba(255,255,255,.16);border-radius:24px;background:#10181c;color:#f4f8f9;box-shadow:0 40px 100px rgba(0,0,0,.5);overflow:hidden;animation:sourceDialogIn .22s ease both}
.source-slides-close{position:absolute;z-index:4;right:18px;top:17px;display:grid;place-items:center;width:42px;height:42px;border:1px solid rgba(255,255,255,.2);border-radius:50%;background:rgba(255,255,255,.08);color:#fff;font-size:27px;line-height:1;cursor:pointer;transition:.18s}
.source-slides-close:hover{background:rgba(255,255,255,.16);transform:rotate(3deg) scale(1.04)}
.source-slides-header{display:flex;align-items:flex-end;justify-content:space-between;gap:30px;min-height:78px;padding:0 58px 14px 4px}
.source-slides-kicker{display:block;color:#82dfd5;font-size:.7rem;font-weight:900;letter-spacing:.16em}
.source-slides-header h2{margin:2px 0 0;font-size:1.35rem;line-height:1.2;color:#fff}
.source-slides-header p{margin:4px 0 0;color:#aab9be;font-size:.82rem}
.source-slides-controls{display:flex;align-items:center;gap:9px;flex:0 0 auto}
.source-slides-controls button{display:inline-flex;align-items:center;gap:7px;height:36px;padding:0 12px;border:1px solid rgba(255,255,255,.18);border-radius:9px;background:rgba(255,255,255,.07);color:#fff;cursor:pointer}
.source-slides-controls button:hover:not(:disabled){background:rgba(255,255,255,.14)}
.source-slides-controls button:disabled,.source-stage-arrow:disabled{opacity:.28;cursor:default}
#sourceSlidesCounter{min-width:65px;text-align:center;color:#d9e4e7;font:700 .78rem ui-monospace,Consolas,monospace}
.source-slides-stage{position:relative;display:grid;grid-template-columns:52px minmax(0,1fr) 52px;align-items:center;flex:1;min-height:0;gap:12px}
.source-slide-frame{position:relative;display:flex;align-items:center;justify-content:center;height:100%;min-height:0;margin:0;border-radius:14px;background:#050a0c;overflow:auto;overscroll-behavior:contain}
.source-slide-frame img{display:block;max-width:100%;max-height:100%;width:auto;height:auto;object-fit:contain;background:#fff;border-radius:6px;box-shadow:0 18px 55px rgba(0,0,0,.42);cursor:zoom-in;transition:.16s opacity,.16s transform}
.source-slide-frame img.zoomed{max-width:none;max-height:none;width:1200px;height:auto;cursor:zoom-out;margin:auto}
.source-slide-frame img.loading{opacity:.15}
.source-slide-loading{position:absolute;z-index:2;left:50%;top:50%;transform:translate(-50%,-50%);padding:9px 13px;border-radius:9px;background:rgba(0,0,0,.68);color:#fff;font-size:.78rem}
.source-slide-frame figcaption{position:absolute;left:50%;bottom:10px;transform:translateX(-50%);padding:5px 11px;border-radius:999px;background:rgba(0,0,0,.66);color:#fff;font-size:.72rem;white-space:nowrap;pointer-events:none}
.source-stage-arrow{display:grid;place-items:center;width:44px;height:76px;border:1px solid rgba(255,255,255,.18);border-radius:13px;background:rgba(255,255,255,.06);color:#fff;font-size:34px;cursor:pointer;transition:.18s}
.source-stage-arrow:hover:not(:disabled){background:rgba(255,255,255,.15);transform:scale(1.04)}
.source-slide-thumbs{display:flex;align-items:center;justify-content:center;gap:8px;min-height:72px;padding:11px 2px 3px;overflow-x:auto}
.source-slide-thumbs button{position:relative;flex:0 0 auto;width:83px;height:62px;padding:3px;border:1px solid rgba(255,255,255,.18);border-radius:8px;background:#202b30;cursor:pointer;overflow:hidden;transition:.16s}
.source-slide-thumbs button.active{border-color:#74d9ce;box-shadow:0 0 0 2px rgba(116,217,206,.25)}
.source-slide-thumbs img{display:block;width:100%;height:100%;object-fit:cover;background:#fff;border-radius:4px}
.source-slide-thumbs span{position:absolute;right:4px;bottom:3px;display:grid;place-items:center;min-width:21px;height:18px;padding:0 4px;border-radius:5px;background:rgba(0,0,0,.72);color:#fff;font:700 .63rem ui-monospace,monospace}
.source-slides-help{margin:7px 0 0;text-align:center;color:#83949a;font-size:.7rem}
@keyframes sourceDialogIn{from{opacity:0;transform:translateY(12px) scale(.985)}to{opacity:1;transform:none}}
html[data-theme="light"] .source-slides-overlay{background:rgba(4,14,17,.9)}
@media(max-width:900px){
  .section-head{flex-wrap:wrap}.section-head .source-slide-btn{margin-left:68px}
  .source-slides-dialog{width:98vw;height:96vh;padding:13px;border-radius:17px}
  .source-slides-header{align-items:flex-start;flex-direction:column;gap:8px;padding:0 50px 10px 2px;min-height:auto}
  .source-slides-controls{width:100%;justify-content:center}
  .source-slides-stage{grid-template-columns:38px minmax(0,1fr) 38px;gap:5px}
  .source-stage-arrow{width:35px;height:60px;font-size:28px}
  .source-slide-thumbs{justify-content:flex-start}.source-slides-help{display:none}
}
@media(max-width:620px){
  .section-head .source-slide-btn{margin-left:0;width:100%}
  .source-slides-overlay{padding:0}
  .source-slides-dialog{width:100vw;height:100vh;border-radius:0;border:0}
  .source-slides-controls button span{display:none}
  .source-slide-thumbs button{width:68px;height:51px}
  .source-slide-frame figcaption{bottom:5px}
}


/* v1.2.1 performance and editor readability */
.lesson-section:not(.hero){content-visibility:auto;contain-intrinsic-size:auto 900px;contain:layout paint style}
.lab-editor{white-space:pre!important;overflow:auto!important;overflow-wrap:normal!important;word-break:normal!important}
.topbar{backdrop-filter:none!important;-webkit-backdrop-filter:none!important;background:var(--paper)!important}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto!important}*,*::before,*::after{animation-duration:.001ms!important;animation-iteration-count:1!important;transition-duration:.001ms!important}}

/* v1.2.2 light-mode editor */
html:not([data-theme="dark"]) .lab-code-pane{background:#fff!important;color:#18333a!important}
html:not([data-theme="dark"]) .lab-code-pane .lab-pane-title{color:#18333a!important;border-color:var(--line)!important}
html:not([data-theme="dark"]) .lab-editor{background:#fff!important;color:#18333a!important;caret-color:#087f8b!important}
html:not([data-theme="dark"]) .lab-prompt{color:#087f8b!important}
html:not([data-theme="dark"]) .lab-mode-badge{background:#edf4f5!important;color:#49646a!important}


/* v3.5.1 legacy-theme bridge: shared labs use the same dark tokens as Lesson 01. */
html[data-theme="dark"] .lab-example-panel{background:color-mix(in srgb,var(--teal) 4%,var(--surface));border-bottom-color:var(--line)}
html[data-theme="dark"] .lab-example-head{border-bottom-color:var(--line)}
html[data-theme="dark"] .lab-example-actions button{background:var(--surface2);color:var(--text);border-color:var(--line)}
html[data-theme="dark"] .lab-example-progress{background:var(--surface2);color:var(--muted)}