:root{--bg:#f4f3ed;--paper:#fffef9;--ink:#253b36;--muted:#65716b;--line:#dce0d5;--green:#264f47;--light:#e7efdf;--orange:#e87951;--gold:#f5d986;--red:#a53d31;--mono:ui-monospace,SFMono-Regular,Consolas,monospace;font-family:Inter,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;color:var(--ink);background:var(--bg);font-synthesis:none}
*{box-sizing:border-box}body{margin:0}button,input,select,textarea{font:inherit;color:inherit}button,a,input,select,summary,textarea{-webkit-tap-highlight-color:transparent}button{cursor:pointer}button:disabled{cursor:default;opacity:.5}button:focus-visible,a:focus-visible,input:focus-visible,select:focus-visible,textarea:focus-visible,summary:focus-visible{outline:3px solid #e87951;outline-offset:4px}a{color:var(--green)}button{border:1px solid var(--line);background:var(--paper);border-radius:10px;padding:11px 15px;min-height:44px;transition:background .15s,transform .15s}button:hover:not(:disabled){background:#edf0e7}button:active:not(:disabled){transform:translateY(1px)}h1,h2,h3,p{margin-top:0}h1{font-family:Georgia,"Times New Roman",serif;font-weight:500;font-size:clamp(34px,4.7vw,64px);line-height:1.02;letter-spacing:-2px;margin-bottom:15px}h2{font-size:23px;letter-spacing:-.6px;margin-bottom:10px}h3{font-size:15px;line-height:1.4}p{line-height:1.55}.muted{color:var(--muted)}.mono,code{font-family:var(--mono)}.eyebrow{font-size:11px;letter-spacing:1.9px;text-transform:uppercase;font-weight:750;color:var(--muted)}.skip{opacity:0;pointer-events:none;position:fixed;left:15px;top:-70px;z-index:20;background:white;padding:15px}.skip:focus{top:10px;opacity:1;pointer-events:auto}
.topbar{height:82px;display:flex;align-items:center;justify-content:space-between;border-bottom:1px solid var(--line);padding:0 max(24px,calc((100vw - 1460px)/2));gap:20px}.brand{display:flex;align-items:center;gap:12px;text-decoration:none;font-size:27px;font-weight:750;letter-spacing:-1px}.brand img{width:32px;height:32px}.brand small{font-size:12px;font-weight:500;color:var(--muted);letter-spacing:0;border-left:1px solid var(--line);padding-left:16px;margin-left:10px}.top-tools{display:flex;gap:12px;align-items:center}.privacy{font-size:12px;color:var(--muted)}.text-button{border:0;background:transparent;padding:9px;font-size:13px}.app-layout{max-width:1460px;margin:auto;display:grid;grid-template-columns:238px minmax(0,1fr);gap:38px;padding:32px 24px 60px}.sidebar{position:sticky;top:20px;align-self:start;min-width:0}.sidebar-title{display:flex;justify-content:space-between;margin:6px 0 18px}.lesson-group{font-size:10px;text-transform:uppercase;letter-spacing:1.5px;color:var(--muted);margin:22px 0 8px}.lesson{display:flex;text-align:left;align-items:center;gap:9px;width:100%;border:0;background:transparent;padding:10px 9px;border-radius:8px;min-height:44px;font-size:13px}.lesson.active{background:var(--green);color:#fffef9}.lesson-num{font-family:var(--mono);font-size:10px;color:#87958d;width:18px}.lesson.active .lesson-num{color:#c1d7c5}.lesson-check{margin-left:auto;color:#8bb286}.sidebar-foot{font-size:12px;line-height:1.6;margin-top:25px;border-top:1px solid var(--line);padding-top:20px;color:var(--muted)}.mobile-menu{display:none}.main{min-width:0}.hero{display:flex;justify-content:space-between;gap:25px;align-items:center;padding:7px 0 24px}.hero-copy{max-width:620px}.hero .eyebrow{margin-bottom:16px}.hero p{max-width:540px;margin-bottom:0;font-size:15px;color:var(--muted)}.hero-mark{width:115px;height:115px;flex-shrink:0;position:relative;display:flex;align-items:center;justify-content:center;border:1px dashed #bbc8b9;border-radius:50%;transform:rotate(-14deg);font-family:var(--mono);font-size:52px;color:#c5cdbf}.hero-mark span{color:var(--orange);font-size:35px}.workspace{background:var(--paper);border:1px solid var(--line);border-radius:19px;overflow:hidden;box-shadow:0 8px 20px #263f3304}.workspace-head{padding:24px 27px 20px;display:flex;justify-content:space-between;gap:20px;align-items:flex-start;border-bottom:1px solid var(--line)}.lesson-title{font-size:22px;margin:8px 0 6px}.pill{font-family:var(--mono);font-size:11px;padding:6px 9px;border:1px solid #cdd8c6;border-radius:6px;white-space:nowrap;background:#f3f6ed;display:inline-block}.case-tools{display:flex;align-items:center;gap:8px;flex-wrap:wrap}.case-tools select{max-width:215px;background:var(--paper);border:1px solid var(--line);border-radius:8px;min-height:44px;padding:8px;font-size:13px}.steps{display:flex;gap:18px;padding:15px 27px;background:#f8f9f2;border-bottom:1px solid var(--line);font-size:11px;color:var(--muted);flex-wrap:wrap}.step{display:flex;align-items:center;gap:7px}.step b{width:20px;height:20px;display:inline-flex;justify-content:center;align-items:center;border-radius:50%;background:#e7e9df;color:#7c857b;font-family:var(--mono);font-size:10px}.step.current{font-weight:700;color:var(--green)}.step.current b{background:var(--green);color:white}.step.past b{background:#d5e5cc;color:var(--green)}.play-grid{display:grid;grid-template-columns:minmax(0,1fr) 270px}.play-main{min-width:0;padding:25px 27px}.insight{padding:24px;background:#f8f9f2;border-left:1px solid var(--line);font-size:13px}.insight p{margin-bottom:18px}.insight h3{font-size:13px}.contract{font-size:14px;line-height:1.6;margin-bottom:20px}.contract .eyebrow{display:block;margin-bottom:7px}.target-row{display:flex;align-items:center;justify-content:space-between;gap:10px;margin:22px 0 10px;font-size:13px}.target{display:flex;align-items:center;gap:9px}.target strong{font-family:var(--mono);font-size:24px;color:var(--green);font-weight:600}.state-label{font-family:var(--mono);font-size:11px;color:var(--muted)}.board-wrap{overflow-x:auto;overscroll-behavior-x:contain;padding:33px 5px 19px;margin:0 -5px;scrollbar-width:thin}.cards{display:flex;gap:7px;width:max-content;min-width:100%;align-items:flex-start;justify-content:center}.card-slot{width:54px;position:relative;flex-shrink:0}.card{height:64px;border:1px solid #ced7c5;border-radius:9px;background:var(--light);display:flex;align-items:center;justify-content:center;font-size:22px;font-family:var(--mono);font-weight:600;transition:.2s}.card-slot.out .card{background:#f0f1eb;border-color:#e4e6de;color:#afb6ad}.card-slot.mid .card{background:var(--gold);border:2px solid 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var(--line);border-radius:8px;background:white;font-family:var(--mono)}.metric{display:flex;justify-content:space-between;padding:9px 0;border-bottom:1px solid var(--line);font-family:var(--mono);font-size:12px}.metric:last-of-type{margin-bottom:20px}.invariant{background:#e8efdf;border:1px solid #d9e3ce;padding:14px;border-radius:9px;font-size:12px;line-height:1.6}.invariant strong{display:block;margin-bottom:7px;font-size:10px;text-transform:uppercase;letter-spacing:1px}.inline-code{font-family:var(--mono);font-size:12px;line-height:1.5}.text-link{padding:0;min-height:30px;background:none;border:0;color:var(--green);font-size:12px;text-decoration:underline;text-underline-offset:3px}.insight details{margin:18px 0}.insight summary{font-weight:600;cursor:pointer;min-height:32px}.insight details p{margin-top:9px;font-size:12px}.below{margin-top:21px}.tabs{display:flex;gap:8px;margin-bottom:12px;overflow-x:auto}.tab{font-size:12px;background:transparent;border-color:transparent;white-space:nowrap}.tab.active{border-color:var(--line);background:var(--paper);font-weight:700}.panel{background:var(--paper);border:1px solid var(--line);padding:24px 26px;border-radius:15px}.panel h3{font-size:16px;margin-bottom:9px}.panel p{font-size:13px;color:var(--muted)}.code{font-family:var(--mono);font-size:12px;line-height:1.8;white-space:pre;overflow-x:auto;background:#263c36;color:#e5eddc;padding:22px;border-radius:10px;margin:16px 0 0}.code-line{display:block;min-height:21px}.code-line.current{background:#f4d78125;box-shadow:-8px 0 0 #e8bb55}.code-line.current:before{content:'›';color:var(--gold);position:absolute;transform:translateX(-16px)}.code-grid{display:grid;grid-template-columns:1fr 1fr;gap:22px}.blank-label{display:block;font-size:12px;margin:14px 0}.blank-label 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@media(min-width:1400px){.card-slot{width:61px}.card{height:70px}}
@media(max-width:1180px){.app-layout{grid-template-columns:210px minmax(0,1fr);gap:24px}.play-grid{grid-template-columns:minmax(0,1fr)}.insight{display:grid;grid-template-columns:1fr 1fr;gap:18px;border-left:0;border-top:1px solid var(--line)}.insight-details{grid-column:1/-1}.hero-mark{display:none}.insight details{margin:0}.workspace-head{flex-wrap:wrap}.card-slot{width:55px}}
@media(max-width:800px){.topbar{height:68px;padding:0 18px}.brand small,.privacy{display:none}.app-layout{display:block;padding:20px 16px 35px}.sidebar{position:static;margin-bottom:22px}.sidebar nav{display:none}.sidebar.expanded nav{display:block}.sidebar-title,.sidebar-foot{display:none}.mobile-menu{display:flex;align-items:center;justify-content:space-between;width:100%;background:var(--paper);font-size:13px}.hero{padding:3px 0 24px}.hero h1{font-size:44px;letter-spacing:-1.6px}.hero p{font-size:14px}.hero .eyebrow{margin-bottom:12px}.workspace-head{padding:21px 20px 18px;gap:15px}.case-tools{width:100%}.case-tools select{max-width:none;flex:1;min-width:0}.steps{padding:13px 20px;gap:12px}.play-main{padding:20px}.insight{padding:20px;gap:20px}.card-slot{width:48px}.card{height:60px;font-size:20px}.cards{gap:6px;justify-content:flex-start}.cards.short{justify-content:center}.code-grid{grid-template-columns:1fr}.panel{padding:20px}.custom{padding:20px}.top-tools{gap:2px}}
@media(max-width:440px){.app-layout{padding:18px 12px 30px}.hero h1{font-size:39px}.workspace-head,.play-main,.insight,.panel,.custom{padding:18px 16px}.steps{padding:12px 16px;gap:10px;font-size:10px}.step b{width:18px;height:18px}.steps .step:first-child{display:none}.moves{gap:7px}.move{padding:11px 10px}.move code{font-size:12px}.move small{font-size:10px}.move kbd{display:none}.insight{grid-template-columns:1fr}.insight-details{grid-column:auto}.target-row{align-items:flex-start}.state-label{font-size:10px;max-width:140px;text-align:right}.card-slot{width:43px}.card{height:56px;font-size:18px}.legend{gap:10px;font-size:9px}.brand{font-size:25px}.comparison-table{font-size:11px}.top-tools button{font-size:12px}.footer{font-size:10px}}
@media(prefers-reduced-motion:reduce){*,*:before,*:after{transition:none!important;scroll-behavior:auto!important}}

@media(max-width:800px){.text-link{min-height:44px}}