@import url('./fonts.css');
:root{--paper:#f7f6f2;--white:#fff;--ink:#2f2939;--muted:#726e78;--line:#e6e3e9;--purple:#7954ad;--purple-dark:#5c358e;--lavender:#eee6f7;--teal:#39786a;--teal-light:#e5f0eb;--error:#aa623c;--error-light:#fcf0e7;--blue:#456b98;--serif:Georgia,'Times New Roman',serif;--sans:'Inter',-apple-system,BlinkMacSystemFont,'Segoe UI',sans-serif;--mono:'SFMono-Regular',Consolas,'Liberation Mono',monospace}
*{box-sizing:border-box}body{margin:0;background:var(--paper);color:var(--ink);font-family:var(--sans);font-size:14px;line-height:1.6;-webkit-font-smoothing:antialiased}button,input,select,textarea{font:inherit}button,a,input,select,summary{ -webkit-tap-highlight-color:transparent}button{cursor:pointer}button:disabled{cursor:default;opacity:.4}button{color:inherit}a{color:inherit}button,select{touch-action:manipulation}button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible,summary:focus-visible,textarea:focus-visible,pre:focus-visible{outline:3px solid var(--purple);outline-offset:4px}button:disabled:hover{transform:none}h1,h2,h3,p{margin:0}svg{display:block}input[type=range]{touch-action:none;width:100%;height:22px;cursor:pointer;accent-color:var(--purple);margin:10px 0 0}input[type=checkbox]{accent-color:var(--purple)}select{background:#fff;border:1px solid var(--line);border-radius:6px;padding:5px 22px 5px 8px;color:var(--ink)}button svg{flex-shrink:0}strong{font-weight:600}small{line-height:1.5}.sr-only{position:absolute!important;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}.skip-link{position:fixed;z-index:100;left:15px;top:-80px;padding:10px;background:#fff;border:2px solid var(--purple)}.skip-link:focus{top:15px}.app-shell{display:grid;grid-template-columns:244px minmax(0,1fr);min-height:100vh}.sidebar{position:sticky;top:0;height:100vh;min-height:740px;padding:35px 21px 23px 24px;border-right:1px solid var(--line);background:#f1f0ec;display:flex;flex-direction:column}.brand{text-decoration:none;display:flex;align-items:center;gap:10px;font-size:21px;letter-spacing:-.7px;font-weight:650}.brand-for{font-weight:400}.brand-icon{background:#362945;border-radius:9px;width:34px;height:34px;color:#e9d7ff;font-family:var(--serif);font-style:italic;font-size:27px;line-height:34px;position:relative;text-align:center}.brand-icon>span{font:11px var(--sans);position:absolute;top:2px;right:3px}.course-meta{margin-top:47px;font-size:9px;letter-spacing:1.7px;color:var(--muted);display:flex;justify-content:space-between;align-items:center}.course-meta>span{padding:1px 5px;border:1px solid #d5d1da;border-radius:4px;letter-spacing:0}.sidebar-title{font-family:var(--serif);font-size:21px;line-height:1.35;letter-spacing:-.3px;margin-top:12px}.sidebar-subtitle{color:var(--muted);font-size:11px;margin:10px 0 25px}.chapter-list{list-style:none;padding:0;margin:0;display:grid;gap:5px}.chapter-button{width:100%;background:transparent;border:1px solid transparent;border-radius:7px;padding:10px 7px;display:flex;align-items:center;gap:10px;text-align:left;font-size:11px;color:#68636e;position:relative;line-height:1.5}.chapter-button:hover{background:#e9e6e9}.chapter-button.active{background:#e6ddf0;color:var(--purple-dark);border-color:#dcd0e8;font-weight:600}.chapter-number{font-family:var(--mono);font-size:10px;width:21px;height:21px;display:grid;place-items:center;border-radius:50%;color:#8c8594}.chapter-button.active .chapter-number{background:var(--purple);color:white}.chapter-number.visited{color:var(--teal)}.tiny-tag{font-size:7px;letter-spacing:.5px;padding:2px 4px;border:1px solid #c8c1cd;border-radius:4px;margin-left:auto}.sidebar-bottom{margin-top:auto;padding-top:38px}.progress-label{display:flex;justify-content:space-between;font-size:9px;color:var(--muted)}progress{appearance:none;-webkit-appearance:none;width:100%;height:4px;display:block;border:0;border-radius:8px;background:#dfdce3;margin:10px 0 12px}progress::-webkit-progress-bar{background:#dfdce3;border-radius:8px}progress::-webkit-progress-value{background:var(--purple);border-radius:8px}progress::-moz-progress-bar{background:var(--purple);border-radius:8px}.sidebar-bottom p{font-size:9px;color:var(--muted)}.reset-lesson{margin-top:15px}.text-button{display:inline-flex;gap:6px;align-items:center;background:transparent;border:0;padding:4px 0;color:var(--muted);font-size:11px;text-decoration:none}.text-button:hover{color:var(--purple-dark)}.primary,.secondary{border-radius:6px;padding:10px 16px;display:inline-flex;justify-content:center;align-items:center;gap:12px;font-size:11px;font-weight:550;line-height:1.5;min-height:38px}.primary{background:#372a47;color:white;border:1px solid #372a47}.primary:hover{background:var(--purple-dark);border-color:var(--purple-dark)}.secondary{background:#fff;border:1px solid #dcd6e4;color:#4f425e}.secondary:hover{background:#f5f0fa}.primary.large{font-size:13px;padding:14px 20px;gap:30px;min-height:48px}.eyebrow{font-family:var(--sans);font-size:9px;letter-spacing:1.5px;line-height:1.7;color:var(--muted);font-weight:550}.muted{color:var(--muted);font-size:10px}.math{font-family:var(--serif);font-variant-numeric:lining-nums}.slope-color{color:var(--purple)}.intercept-color{color:var(--teal)}.input-color{color:var(--blue)}.error-color{color:var(--error)}.intro{padding:78px clamp(30px,5vw,85px) 32px;display:grid;grid-template-columns:1fr 1fr;align-content:center;gap:60px 38px;max-width:1500px;min-height:100vh}.intro-copy{padding-top:10px}.intro-copy>.eyebrow{color:var(--purple-dark)}.intro h1{font-family:var(--serif);font-weight:400;font-size:clamp(37px,4vw,64px);line-height:1.1;letter-spacing:-2.1px;margin:25px 0}.intro h1 em{font-weight:400;color:var(--purple);font-style:italic}.intro-lead{font-size:17px;line-height:1.7;max-width:400px;color:#4a4354;margin-bottom:14px}.intro-copy>p:not(.intro-lead){color:var(--muted);font-size:12px;line-height:1.9;max-width:350px}.intro-copy>.primary{margin-top:29px}.intro-notes{display:flex;flex-wrap:wrap;gap:10px 20px;font-size:9px;color:var(--muted);margin-top:23px;max-width:340px}.intro-notes span:before{content:'·';margin-right:6px;color:var(--purple)}.intro-art{position:relative;background:#fff;border:1px solid var(--line);border-radius:10px;align-self:center;padding:30px 12px 24px;box-shadow:0 14px 35px #33274405;transform:rotate(-1.3deg)}.intro-art .plot{margin:14px 0 0}.paper-corner{font-size:8px;letter-spacing:1.7px;color:var(--muted);margin-left:25px}.intro-equation{font-family:var(--serif);font-size:34px;text-align:center;letter-spacing:2px}.intro-art>p{text-align:center;color:var(--muted);font-size:9px;margin:10px 12px 0}.art-note{position:absolute;right:0;bottom:-45px;font-family:var(--serif);font-style:italic;font-size:16px;line-height:1.3;color:var(--purple);transform:rotate(6deg)}.intro-bottom{grid-column:1/-1;display:flex;gap:18px;border-top:1px solid var(--line);padding-top:30px;margin-top:12px}.small-orbit{height:38px;width:38px;display:grid;place-items:center;background:var(--lavender);color:var(--purple);border-radius:50%;font-size:22px;flex-shrink:0}.intro-bottom strong{font-size:12px}.intro-bottom p{font-size:11px;color:var(--muted);margin-top:4px}.planned{grid-column:1/-1;max-width:700px;font-size:11px;color:var(--muted);margin-top:-30px}.planned summary{cursor:pointer}.planned p{margin-top:10px}.workspace{padding:35px clamp(22px,3vw,52px) 22px;max-width:1600px;width:100%;margin:auto}.workspace-header{display:flex;align-items:center;justify-content:space-between;gap:24px;margin-bottom:27px;min-height:110px}.workspace-header h1{font-family:var(--serif);font-weight:400;letter-spacing:-1.1px;font-size:clamp(27px,2.4vw,38px);line-height:1.2;margin:12px 0 10px}.workspace-header h1:focus{outline:0}.workspace-header p{font-size:12px;color:var(--muted)}.header-slash{color:#bbb4c2;margin:0 10px}.header-tag{font-size:8px;letter-spacing:1.1px;text-align:right;white-space:nowrap;color:var(--purple);padding-top:15px}.header-tag>span{display:block;font-size:9px;letter-spacing:0;color:var(--muted);margin-top:5px}.learning-grid{display:grid;grid-template-columns:minmax(0,1fr) 262px;align-items:start;gap:23px}.visual-panel{background:var(--white);border:1px solid var(--line);border-radius:9px;min-width:0;padding:24px 25px 0;overflow:hidden}.visual-heading{display:flex;align-items:center;justify-content:space-between;gap:12px;min-height:25px;margin-bottom:15px}.visual-heading>.eyebrow{color:#62576e;font-size:8px;letter-spacing:1.3px}.visual-heading>.text-button{font-size:9px}.plot{width:100%;height:auto;margin-top:5px}.grid-line{stroke:#eeeaf1;stroke-width:1}.axis-line{stroke:#d4cddc;stroke-width:1}.axis-tick{fill:#8b8394;font:11px var(--sans)}.axis-label{fill:#736a7e;font:italic 17px var(--serif)}.axis-caption{fill:#8c8495;font:10px var(--sans);letter-spacing:1px}.observation circle{fill:var(--teal);stroke:#fff;stroke-width:2}.observation.selected-point circle{stroke:var(--teal);stroke-width:2;fill:#fff}.point-label{fill:#667b72;font:11px var(--mono)}.model-line{stroke:var(--purple);stroke-width:2.5}.prediction-point{fill:var(--purple);stroke:#fff;stroke-width:2}.prediction-label{fill:var(--purple);font:12px var(--mono)}.input-guide{stroke:var(--purple);stroke-opacity:.25;stroke-dasharray:3 4}.residual-line{stroke:var(--error);stroke-dasharray:4 4;stroke-width:1;opacity:.3}.residual-line.chosen{opacity:1;stroke-width:2}.error-square{fill:#dcab7830;stroke:#c18b5d;stroke-width:1;stroke-dasharray:3 3}.legend{display:flex;align-items:center;justify-content:center;flex-wrap:wrap;gap:10px 18px;font-size:9px;color:var(--muted);margin:3px 0 24px}.legend>span{display:flex;align-items:center;gap:6px}.legend i{display:inline-block}.legend-dot{width:7px;height:7px;border-radius:50%;background:var(--teal)}.legend-diamond{width:7px;height:7px;transform:rotate(45deg);background:var(--purple)}.legend-line{height:2px;width:14px;background:var(--purple)}.legend-gap{width:13px;border-top:2px dashed var(--error)}.context-panel{display:flex;flex-direction:column;gap:22px;padding:6px 0 0}.step-caption{padding:0 3px}.step-count{font-family:var(--mono);font-size:12px;display:block;margin:1px 0 14px;color:var(--purple)}.step-count>span{color:#a9a0b2;font-size:10px}.step-caption h2{font-family:var(--serif);font-size:24px;line-height:1.3;font-weight:400;letter-spacing:-.3px;margin:8px 0 12px}.step-caption p,.context-panel p{font-size:11px;line-height:1.85;color:#6b6374}.takeaway{background:#ece9e6;padding:15px 17px;border-radius:6px}.takeaway .eyebrow{font-size:7px}.takeaway p{margin-top:5px;font-size:10px}.symbol-inspector{background:#f1ebf7;border:1px solid #e2d8ee;border-radius:7px;padding:17px}.inspector-top{display:flex;align-items:center;gap:12px}.inspector-glyph{min-width:32px;font-size:30px;color:var(--purple-dark);line-height:1.3}.inspector-top .eyebrow{font-size:6.5px;letter-spacing:1.2px}.inspector-top h3{font-size:11px;line-height:1.4;font-weight:550}.symbol-inspector .pronunciation{font-family:var(--serif);font-style:italic;font-size:12px;color:var(--purple-dark);margin:12px 0 6px}.symbol-inspector p{font-size:10px;line-height:1.8}.symbol-value{margin-top:14px;padding-top:12px;border-top:1px solid #ddd1e9;font-size:9px;color:#7d6c8e;display:flex;flex-direction:column;gap:3px}.symbol-value strong{font:12px var(--mono);color:var(--purple-dark);overflow-wrap:anywhere}.symbol-inspector>small{display:block;color:#8d7a9e;font-size:8px;margin-top:13px}.context-python{padding:15px 3px;border-top:1px solid var(--line)}.context-python .eyebrow{font-size:7px}.context-python code{display:block;margin-top:7px;font-size:9px;overflow-wrap:anywhere;color:#65576f}.step-controls{border-top:1px solid var(--line);display:flex;align-items:center;gap:15px;margin:24px -25px 0;padding:12px 20px;background:#fcfbfd;flex-wrap:wrap}.step-buttons{display:flex;align-items:center;gap:5px}.icon-button{background:white;border:1px solid var(--line);border-radius:5px;width:30px;height:30px;display:inline-flex;align-items:center;justify-content:center;padding:0}.icon-button:hover{background:var(--lavender)}.step-position{font-size:9px;color:var(--muted)}.speed-label{font-size:9px;color:var(--muted);display:flex;gap:6px;align-items:center;margin-left:auto}.speed-label select{font-size:9px;padding:3px}.motion-note{font-size:8px;color:var(--muted);width:100%}.lesson-footer{display:flex;justify-content:space-between;align-items:center;gap:14px;margin-top:23px;padding-bottom:10px}.footer-note{color:#9a929f;font-size:9px}.algebra-flow{display:flex;gap:14px;align-items:center;justify-content:center;padding:65px 0 40px}.flow-node{border:1px solid #e6e0ee;border-radius:8px;padding:18px 8px;width:140px;text-align:center;flex:1;max-width:150px;position:relative;opacity:.55;background:#faf9fb}.flow-node.revealed{opacity:1}.flow-node.flow-active{border-color:#b997d7;background:#f4effa;box-shadow:0 4px 18px #9a6dbf0d}.flow-node>span{display:block;font-size:8px;letter-spacing:1.4px;color:var(--purple)}.flow-node strong{font:48px var(--serif);display:block;line-height:1.3;margin:10px 0;color:#3d2e4b}.flow-node small{font-size:9px;color:#93839f}.flow-node:first-child strong{color:var(--blue)}.flow-node:last-child strong{color:var(--teal)}.flow-arrow{color:#b6a5c6;font:23px var(--serif)}.algebra-equation{font-size:36px;letter-spacing:3px;text-align:center;margin:0 0 15px}.visual-caption{font-size:11px;text-align:center;color:var(--muted);margin:0 0 32px}.input-control{padding:20px 26px;background:#f8f6fb;border:1px solid #eee7f5;border-radius:7px;max-width:430px;margin:0 auto}.input-control label,.slider-block label{display:flex;justify-content:space-between;font-size:11px;font-weight:550}.input-control label{color:var(--blue)}output{font-family:var(--mono);font-size:12px}.range-ends{display:flex;justify-content:space-between;font-size:8px;color:var(--muted)}.python-bridge{display:flex;align-items:center;gap:20px;margin:40px 0 20px;padding-top:20px;border-top:1px solid var(--line);justify-content:center;flex-wrap:wrap}.python-bridge>span{font-size:7px;letter-spacing:1.2px;color:var(--muted)}.python-bridge code{font-size:12px}.python-bridge small{font-size:9px;color:var(--muted)}.formula-card{background:#f7f4fb;border:1px solid #e9e1f1;border-radius:7px;text-align:center;padding:17px 18px 12px}.formula{display:flex;gap:7px;align-items:center;justify-content:center;flex-wrap:wrap;line-height:1.3;font-size:33px}.symbol{background:transparent;border:0;padding:1px 2px;border-bottom:1px dashed #c3afda;font:inherit;min-height:35px;color:inherit;white-space:nowrap}.symbol:hover,.symbol.inspected{background:#e7daf5;border-radius:4px;border-bottom-color:var(--purple)}.symbol-prediction,.symbol-indexed{color:var(--purple)}.symbol-w{color:var(--purple)}.symbol-x{color:var(--blue)}.symbol-b,.symbol-y{color:var(--teal)}.symbol-square,.symbol-minus{color:var(--error)}.formula .times:empty{margin-left:-9px}.formula-card>p{font-size:10px;color:var(--muted);margin-top:9px}.numeric-rule{display:flex;gap:20px;align-items:center;justify-content:center;border-top:1px solid #e5dced;padding-top:12px;margin-top:14px}.numeric-rule>span{font-size:8px;letter-spacing:1px;text-transform:uppercase;color:var(--muted)}.numeric-rule code{font-size:12px;color:var(--purple-dark)}.checkbox-label{display:flex;align-items:center;gap:5px;font-size:9px;color:var(--muted)}.observation-selector{border:0;margin:20px 0 2px;padding:0;display:flex;gap:6px;align-items:center}.observation-selector legend{font-size:8px;text-transform:uppercase;letter-spacing:1px;color:var(--muted);margin-bottom:9px}.observation-selector button{background:#fff;border:1px solid var(--line);padding:6px 10px;border-radius:5px;flex:1;color:var(--muted);font:10px var(--mono);display:flex;justify-content:center;align-items:center;gap:10px;min-height:32px}.observation-selector button span{color:#aca3b4;font-size:8px}.observation-selector button[aria-pressed=true]{border-color:#b49acb;background:#f3edf9;color:var(--purple-dark)}.parameter-controls{display:grid;grid-template-columns:1fr 1fr;gap:28px;margin:16px 0 22px;padding:0 2px}.slider-block:nth-child(2) input{accent-color:var(--teal)}.stats-strip{display:grid;grid-template-columns:1fr 1fr 1.4fr;border:1px solid var(--line);border-radius:7px;padding:13px 0;margin:10px 0 22px}.stats-strip>div{padding:0 16px;border-right:1px solid var(--line)}.stats-strip>div:last-child{border:0}.stat-key{font-size:8px;display:block;margin-bottom:2px}.stats-strip strong{font:21px var(--serif);font-variant-numeric:tabular-nums}.stats-strip>div:last-child strong{color:var(--error)}.prediction-check{background:#f8f6fa;border-radius:7px;padding:17px 18px;font-size:10px;margin-bottom:19px}.prediction-check>strong{font-size:10px}.prediction-check>p{color:var(--muted);margin-top:5px}.choice-chips{display:flex;gap:7px;margin:12px 0;flex-wrap:wrap}.choice-chips>button{font-size:9px;line-height:1.5;padding:7px 9px;border:1px solid #e2dbe9;border-radius:5px;background:white;text-align:left}.choice-chips>button.selected{border-color:var(--purple);background:var(--lavender)}.preset-row{display:flex;gap:7px;align-items:center;font-size:8px;flex-wrap:wrap}.preset-row>span{margin-right:auto;color:var(--muted)}.preset-row>button{font-size:9px;padding:5px 8px;border:1px solid var(--line);background:#fff;border-radius:4px}.preset-row>button:hover{border-color:var(--purple)}.inline-feedback{font-size:10px;padding:11px;background:var(--teal-light);border-radius:5px;color:var(--teal)!important;margin-top:12px!important}.error-calculation{display:grid;grid-template-columns:1fr 1fr;gap:20px;border-top:1px solid var(--line);padding:24px 0 8px;margin-top:24px}.error-calculation>div>span{font-size:8px;color:var(--muted);display:block}.error-calculation strong{display:block;font-size:27px;line-height:1.4;margin:8px 0}.error-calculation small{font-size:9px;color:var(--muted)}.dimmed{opacity:.4}.insight{background:#f8f1e9;border-radius:6px;padding:15px;font-size:11px;color:#93623e;margin:18px 0 3px}.insight p{font-size:10px;margin-top:6px;color:#a17b5b}.loss-table-wrap{overflow-x:auto;margin:6px 0 23px}.loss-table{width:100%;border-collapse:collapse;font-size:10px;text-align:right;white-space:nowrap}.loss-table caption{text-align:left;color:var(--muted);font-size:9px;caption-side:bottom;padding-top:10px}.loss-table th{font-weight:400}.loss-table thead{color:#8d8097;font-size:8px;background:#f8f6fa}.loss-table thead th{padding:9px 7px}.loss-table tbody td,.loss-table tbody th{padding:9px 8px;border-bottom:1px solid #f0ecf4;font-family:var(--mono)}.loss-table tbody th{text-align:center}.loss-table tbody th>button{font:9px var(--mono);border:1px solid transparent;background:transparent;border-radius:4px;width:24px;height:24px;color:var(--muted)}.loss-table .chosen-row{background:#faf7fd}.loss-table .chosen-row th>button{border-color:#cfbbdf;color:var(--purple)}.square-cell{color:var(--error);font-weight:600}.expanded-loss{border:1px solid #eadfce;background:#fcf9f4;border-radius:6px;padding:17px 14px;text-align:center;min-height:126px}.expanded-loss 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