:root {
      --ink: #171713;
      --paper: #f3f0e6;
      --paper-2: #e7e2d4;
      --orange: #ff5a36;
      --lime: #c8f45b;
      --teal: #0b7f79;
      --blue: #235ee7;
      --muted: #69685f;
      --line: #171713;
      --white: #fffdf6;
      --shadow: 5px 5px 0 var(--ink);
      --radius: 14px;
      --sans: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
      --mono: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
    }

    * { box-sizing: border-box; }
    html { scroll-behavior: smooth; }
    body {
      margin: 0;
      color: var(--ink);
      background:
        linear-gradient(rgba(23,23,19,.035) 1px, transparent 1px),
        linear-gradient(90deg, rgba(23,23,19,.035) 1px, transparent 1px),
        var(--paper);
      background-size: 24px 24px;
      font-family: var(--sans);
      line-height: 1.55;
    }
    button, input { font: inherit; }
    button, a { -webkit-tap-highlight-color: transparent; }
    a { color: inherit; }
    :focus-visible { outline: 3px solid var(--blue); outline-offset: 3px; }
    ::selection { background: var(--lime); color: var(--ink); }

    .skip-link {
      position: fixed; top: 10px; left: 10px; z-index: 100;
      transform: translateY(-150%); padding: 10px 14px; background: var(--ink); color: white;
    }
    .skip-link:focus { transform: translateY(0); }
    .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; }

    .topbar {
      position: sticky; top: 0; z-index: 30; height: 70px;
      display: flex; align-items: center; gap: 22px; padding: 0 28px;
      border-bottom: 2px solid var(--line); background: rgba(243,240,230,.94);
      backdrop-filter: blur(12px);
    }
    .brand { display: inline-flex; align-items: center; gap: 10px; text-decoration: none; font-weight: 900; letter-spacing: -.04em; }
    .brand-mark { display: grid; place-items: center; width: 34px; height: 34px; border: 2px solid var(--ink); border-radius: 9px; background: var(--orange); }
    .brand-mark svg { width: 22px; }
    .brand span:last-child { font-size: 18px; }
    .top-nav { display: flex; align-items: center; gap: 4px; margin-left: auto; }
    .top-nav a { padding: 8px 11px; border-radius: 8px; color: var(--muted); font-size: 14px; font-weight: 750; text-decoration: none; }
    .top-nav a:hover, .top-nav a[aria-current="page"] { color: var(--ink); background: var(--paper-2); }
    .progress-pill { display: flex; align-items: center; gap: 10px; min-width: 152px; margin-left: 12px; font: 700 12px var(--mono); }
    .progress-track { flex: 1; height: 9px; border: 2px solid var(--ink); border-radius: 10px; background: var(--white); overflow: hidden; }
    .progress-fill { width: 0; height: 100%; background: var(--lime); transition: width .35s ease; }
    .menu-btn { display: none; margin-left: auto; width: 42px; height: 42px; border: 2px solid var(--ink); border-radius: 10px; background: var(--white); cursor: pointer; }

    .layout { min-height: calc(100vh - 70px); }
    .sidebar {
      position: fixed; inset: 70px auto 0 0; z-index: 20; width: 254px; padding: 22px 16px;
      border-right: 2px solid var(--line); background: var(--paper); overflow-y: auto;
    }
    .side-label { margin: 0 10px 10px; color: var(--muted); font: 700 11px var(--mono); letter-spacing: .12em; text-transform: uppercase; }
    .lesson-nav { display: grid; gap: 6px; }
    .lesson-link {
      display: grid; grid-template-columns: 28px 1fr auto; align-items: center; gap: 8px;
      min-height: 44px; padding: 8px 10px; border: 2px solid transparent; border-radius: 10px;
      color: var(--muted); text-decoration: none; font-size: 13px; font-weight: 750;
    }
    .lesson-link:hover { color: var(--ink); background: var(--paper-2); }
    .lesson-link[aria-current="page"] { color: var(--ink); border-color: var(--ink); background: var(--white); box-shadow: 3px 3px 0 var(--ink); }
    .lesson-link.locked { color: var(--muted); }
    .lesson-link.locked .lesson-check { border-style: dashed; font-size: 9px; }
    .lesson-num { color: var(--muted); font: 700 11px var(--mono); }
    .lesson-check { display: grid; place-items: center; width: 18px; height: 18px; border: 1.5px solid var(--ink); border-radius: 50%; font-size: 11px; }
    .lesson-check.done { background: var(--lime); }
    .side-tip { margin-top: 24px; padding: 14px; border: 2px solid var(--ink); border-radius: 12px; background: var(--lime); font-size: 12px; box-shadow: 3px 3px 0 var(--ink); }
    .side-tip strong { display: block; margin-bottom: 4px; font-family: var(--mono); }

    main { margin-left: 254px; min-height: calc(100vh - 70px); }
    .page { display: none; animation: enter .3s ease both; }
    .page.active { display: block; }
    @keyframes enter { from { opacity: 0; transform: translateY(8px); } }

    .home { max-width: 1400px; margin: 0 auto; padding: 48px clamp(24px,5vw,76px) 72px; }
    .eyebrow { display: inline-flex; align-items: center; gap: 8px; margin-bottom: 18px; font: 750 12px var(--mono); letter-spacing: .12em; text-transform: uppercase; }
    .eyebrow::before { content: ""; width: 28px; height: 8px; border-radius: 10px; background: var(--orange); }
    .hero { display: grid; grid-template-columns: minmax(0,1.05fr) minmax(380px,.95fr); align-items: center; gap: clamp(38px,6vw,92px); min-height: 580px; }
    h1 { max-width: 780px; margin: 0; font-size: clamp(56px,7.7vw,118px); line-height: .86; letter-spacing: -.075em; }
    .outline { color: var(--paper); -webkit-text-stroke: 2px var(--ink); text-shadow: 4px 4px 0 var(--lime); }
    .hero-copy { max-width: 610px; margin: 28px 0; color: #46463f; font-size: clamp(17px,1.5vw,21px); }
    .hero-actions { display: flex; flex-wrap: wrap; align-items: center; gap: 14px; }
    .btn {
      display: inline-flex; align-items: center; justify-content: center; gap: 9px; min-height: 48px;
      padding: 11px 18px; border: 2px solid var(--ink); border-radius: 10px; background: var(--ink); color: white;
      box-shadow: 4px 4px 0 var(--orange); font-weight: 850; text-decoration: none; cursor: pointer;
      transition: transform .15s, box-shadow .15s;
    }
    .btn:hover { transform: translate(2px,2px); box-shadow: 2px 2px 0 var(--orange); }
    .btn.secondary { background: var(--white); color: var(--ink); box-shadow: none; }
    .btn.small { min-height: 40px; padding: 8px 13px; font-size: 13px; box-shadow: 3px 3px 0 var(--orange); }
    .hero-note { color: var(--muted); font: 12px var(--mono); }

    .terminal-card { position: relative; width: 100%; max-width: 600px; min-width: 0; transform: rotate(1.2deg); }
    .terminal-back { position: absolute; inset: -18px 20px 24px -20px; border: 2px solid var(--ink); border-radius: 20px; background: var(--orange); transform: rotate(-4deg); }
    .terminal-window { position: relative; border: 2px solid var(--ink); border-radius: 15px; overflow: hidden; background: #161816; color: #eaf6d2; box-shadow: 10px 12px 0 var(--ink); }
    .window-bar { display: flex; align-items: center; gap: 7px; height: 42px; padding: 0 14px; border-bottom: 2px solid #000; background: #e5e1d6; color: var(--ink); font: 700 11px var(--mono); }
    .dot { width: 11px; height: 11px; border: 1.5px solid var(--ink); border-radius: 50%; }
    .dot:nth-child(1) { background: var(--orange); }
    .dot:nth-child(2) { background: #ffd94a; }
    .dot:nth-child(3) { background: var(--lime); }
    .window-title { margin: 0 auto; transform: translateX(-22px); }
    .terminal-body { min-height: 350px; padding: clamp(20px,4vw,34px); font: 14px/1.9 var(--mono); }
    .prompt { color: var(--lime); }
    .cmd { color: #fff; }
    .comment { color: #7d8279; }
    .terminal-output { color: #69dbe1; }
    .cursor { display: inline-block; width: 8px; height: 17px; margin-left: 4px; vertical-align: middle; background: var(--lime); animation: blink 1s steps(1) infinite; }
    @keyframes blink { 50% { opacity: 0; } }
    .sticker { position: absolute; right: -20px; bottom: -24px; display: grid; place-items: center; width: 108px; height: 108px; border: 2px solid var(--ink); border-radius: 50%; background: var(--lime); font: 900 13px/1.1 var(--mono); text-align: center; transform: rotate(-9deg); }

    .stats { display: grid; grid-template-columns: repeat(3,1fr); margin: 34px 0 70px; border: 2px solid var(--ink); border-radius: 14px; background: var(--white); box-shadow: var(--shadow); overflow: hidden; }
    .stat { padding: 24px; }
    .stat + .stat { border-left: 2px solid var(--ink); }
    .stat strong { display: block; font-size: 32px; line-height: 1; letter-spacing: -.04em; }
    .stat span { color: var(--muted); font: 12px var(--mono); }

    .section-head { display: flex; align-items: end; justify-content: space-between; gap: 20px; margin-bottom: 24px; }
    .section-head h2 { margin: 0; font-size: clamp(34px,4vw,58px); line-height: 1; letter-spacing: -.055em; }
    .section-head p { max-width: 430px; margin: 0; color: var(--muted); }
    .module-grid { display: grid; grid-template-columns: repeat(2, minmax(0,1fr)); gap: 18px; }
    .module-card {
      display: grid; grid-template-columns: 70px 1fr auto; align-items: center; gap: 18px; min-height: 150px;
      padding: 22px; border: 2px solid var(--ink); border-radius: var(--radius); background: var(--white); text-decoration: none;
      transition: transform .16s, box-shadow .16s;
    }
    .module-card:hover { transform: translateY(-3px); box-shadow: 6px 6px 0 var(--ink); }
    .module-card.locked { border-style: dashed; background: var(--paper-2); }
    .module-card.locked:hover { transform: none; box-shadow: none; }
    .module-card.locked .module-icon { filter: grayscale(1); }
    .module-icon { display: grid; place-items: center; width: 66px; height: 66px; border: 2px solid var(--ink); border-radius: 16px; font: 900 22px var(--mono); }
    .module-card:nth-child(4n+1) .module-icon { background: var(--orange); }
    .module-card:nth-child(4n+2) .module-icon { background: var(--lime); }
    .module-card:nth-child(4n+3) .module-icon { background: #86b2ff; }
    .module-card:nth-child(4n) .module-icon { background: #f6c7e0; }
    .module-card h3 { margin: 0 0 4px; font-size: 19px; }
    .module-card p { margin: 0; color: var(--muted); font-size: 13px; }
    .module-card .duration { margin-top: 10px; font: 11px var(--mono); }
    .arrow { font-size: 28px; }

    .principles { display: grid; grid-template-columns: .8fr 1.2fr; gap: 30px; margin-top: 80px; padding: clamp(28px,5vw,60px); border: 2px solid var(--ink); border-radius: 18px; background: var(--teal); color: white; box-shadow: 8px 8px 0 var(--ink); }
    .principles h2 { margin: 0; font-size: clamp(36px,4vw,62px); line-height: .95; letter-spacing: -.06em; }
    .principle-list { display: grid; gap: 12px; }
    .principle { display: grid; grid-template-columns: 42px 1fr; gap: 14px; padding: 15px; border: 1px solid rgba(255,255,255,.4); border-radius: 12px; background: rgba(0,0,0,.12); }
    .principle b { color: var(--lime); font: 800 14px var(--mono); }
    .principle p { margin: 0; font-size: 14px; }

    .lesson-page { max-width: 1100px; margin: 0 auto; padding: 54px clamp(24px,6vw,80px) 80px; }
    .lesson-hero { display: grid; grid-template-columns: 1fr auto; gap: 32px; align-items: end; padding-bottom: 34px; border-bottom: 2px solid var(--ink); }
    .lesson-kicker { color: var(--teal); font: 800 12px var(--mono); letter-spacing: .12em; text-transform: uppercase; }
    .lesson-hero h1 { max-width: 800px; margin-top: 10px; font-size: clamp(50px,7vw,88px); line-height: .9; }
    .lesson-meta { display: flex; gap: 18px; margin-top: 22px; color: var(--muted); font: 12px var(--mono); }
    .lesson-badge { display: grid; place-items: center; width: 110px; height: 110px; border: 2px solid var(--ink); border-radius: 28px; background: var(--lime); box-shadow: var(--shadow); font: 900 25px var(--mono); transform: rotate(3deg); }
    .lesson-intro { max-width: 780px; margin: 34px 0 42px; font-size: 20px; line-height: 1.65; }
    .lesson-content { display: grid; grid-template-columns: minmax(0,1fr) 210px; gap: 60px; align-items: start; }
    .lesson-content > * { min-width: 0; }
    .article h2 { margin: 48px 0 14px; font-size: 32px; letter-spacing: -.04em; }
    .article h2:first-child { margin-top: 0; }
    .article h3 { margin: 28px 0 8px; font-size: 20px; }
    .article p { color: #3d3d37; }
    .article ul { padding-left: 22px; }
    .article li { margin: 7px 0; }
    .toc { position: sticky; top: 94px; padding: 16px; border-left: 2px solid var(--ink); }
    .toc strong { display: block; margin-bottom: 10px; font: 800 11px var(--mono); letter-spacing: .1em; text-transform: uppercase; }
    .toc a { display: block; padding: 6px 0; color: var(--muted); font-size: 13px; text-decoration: none; }
    .toc a:hover { color: var(--ink); }
    .code-block { position: relative; margin: 20px 0; border: 2px solid var(--ink); border-radius: 12px; background: #171916; color: #eef6dd; overflow: hidden; }
    .code-label { display: flex; justify-content: space-between; padding: 8px 12px; border-bottom: 1px solid #40423d; color: #b2b5ac; font: 10px var(--mono); text-transform: uppercase; }
    .copy-btn { border: 0; background: transparent; color: var(--lime); font: 700 10px var(--mono); cursor: pointer; }
    pre { margin: 0; padding: 18px; overflow-x: auto; font: 13px/1.75 var(--mono); white-space: pre; }
    code { font-family: var(--mono); }
    p code, li code { padding: 2px 5px; border: 1px solid #c8c3b7; border-radius: 5px; background: var(--paper-2); color: #b52f17; font-size: .88em; }
    .callout { margin: 22px 0; padding: 18px 20px; border: 2px solid var(--ink); border-radius: 12px; background: var(--lime); box-shadow: 4px 4px 0 var(--ink); }
    .callout.warning { background: #ffd151; }
    .callout strong { display: block; margin-bottom: 4px; font: 850 12px var(--mono); text-transform: uppercase; }
    .callout p { margin: 0; color: var(--ink); }
    .table-wrap { margin: 20px 0; border: 2px solid var(--ink); border-radius: 12px; overflow-x: auto; }
    table { width: 100%; border-collapse: collapse; background: var(--white); font-size: 14px; }
    th, td { padding: 12px 14px; border-bottom: 1px solid #c8c3b7; text-align: left; }
    th { background: var(--paper-2); font: 800 11px var(--mono); text-transform: uppercase; }
    tr:last-child td { border-bottom: 0; }
    .try-it { margin: 34px 0; padding: 22px; border: 2px solid var(--ink); border-radius: 14px; background: #dce7ff; }
    .try-it h3 { margin-top: 0; }
    .try-it ol { padding-left: 20px; }
    .lesson-footer { display: flex; align-items: center; justify-content: space-between; gap: 20px; margin-top: 56px; padding-top: 24px; border-top: 2px solid var(--ink); }
    .complete-btn.done { background: var(--lime); color: var(--ink); box-shadow: 4px 4px 0 var(--ink); }
    .access-badge { display: inline-flex; align-items: center; min-height: 24px; padding: 3px 8px; border: 1.5px solid var(--ink); border-radius: 999px; color: var(--ink); font: 800 9px var(--mono); letter-spacing: .08em; text-transform: uppercase; }
    .access-badge--free { background: #dce7ff; }
    .access-badge--premium { background: #ffd151; }
    .access-badge--pro { background: var(--orange); }
    .locked-button { cursor: not-allowed; }
    .locked-page { min-height: 620px; padding-top: 10px; }
    .locked-panel { max-width: 760px; margin-top: 28px; padding: clamp(26px,5vw,52px); border: 2px dashed var(--ink); border-radius: 18px; background: var(--white); box-shadow: 8px 8px 0 var(--ink); }
    .locked-panel__icon { display: grid; place-items: center; width: 68px; height: 68px; margin-bottom: 22px; border: 2px solid var(--ink); border-radius: 18px; background: var(--paper-2); font-size: 28px; transform: rotate(-3deg); }
    .locked-panel h1 { margin: 20px 0 16px; font-size: clamp(44px,7vw,78px); }
    .locked-panel p { max-width: 600px; color: var(--muted); font-size: 18px; }
    .locked-panel .locked-panel__note { margin: 24px 0; padding: 12px 14px; border-left: 3px solid var(--orange); background: var(--paper); font: 12px/1.6 var(--mono); }

    .tool-page { max-width: 1180px; margin: 0 auto; padding: 54px clamp(24px,6vw,80px) 90px; }
    .tool-page > h1 { font-size: clamp(52px,7vw,90px); }
    .tool-intro { max-width: 700px; color: var(--muted); font-size: 18px; }
    .search-box { position: relative; margin: 36px 0 20px; }
    .search-box input { width: 100%; height: 58px; padding: 0 54px 0 18px; border: 2px solid var(--ink); border-radius: 12px; background: var(--white); box-shadow: 4px 4px 0 var(--ink); font-family: var(--mono); }
    .search-box span { position: absolute; right: 18px; top: 16px; font-size: 20px; }
    .filter-row { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 28px; }
    .filter { padding: 7px 12px; border: 1.5px solid var(--ink); border-radius: 999px; background: var(--white); font: 700 11px var(--mono); cursor: pointer; }
    .filter.active { background: var(--ink); color: white; }
    .command-grid { display: grid; grid-template-columns: repeat(2,minmax(0,1fr)); gap: 12px; }
    .command-item { padding: 18px; border: 2px solid var(--ink); border-radius: 12px; background: var(--white); }
    .command-item header { display: flex; align-items: center; justify-content: space-between; gap: 10px; }
    .command-item h3 { margin: 0; color: var(--teal); font: 800 17px var(--mono); }
    .command-tag { padding: 3px 7px; border-radius: 5px; background: var(--paper-2); color: var(--muted); font: 10px var(--mono); }
    .command-item p { margin: 8px 0; color: var(--muted); font-size: 13px; }
    .command-example { display: block; padding: 8px 10px; border-radius: 7px; background: #171916; color: var(--lime); font: 12px var(--mono); }
    .empty { display: none; padding: 30px; text-align: center; color: var(--muted); }

    .lab-shell { display: grid; grid-template-columns: 1fr 280px; gap: 24px; margin-top: 36px; }
    .lab-terminal { min-height: 470px; border: 2px solid var(--ink); border-radius: 14px; background: #151715; color: #ecf5dc; box-shadow: 7px 7px 0 var(--ink); overflow: hidden; }
    .lab-output { height: 385px; padding: 20px; overflow-y: auto; font: 13px/1.65 var(--mono); white-space: pre-wrap; }
    .lab-line { margin-bottom: 7px; }
    .lab-line.command { color: white; }
    .lab-line.output { color: #aeb4a5; }
    .lab-line.success { color: var(--lime); }
    .lab-input-row { display: flex; align-items: center; gap: 9px; height: 58px; padding: 0 18px; border-top: 1px solid #454740; font: 13px var(--mono); }
    .lab-prompt { color: var(--lime); white-space: nowrap; }
    .lab-input { flex: 1; border: 0; outline: 0; background: transparent; color: white; font: 13px var(--mono); }
    .lab-guide { padding: 20px; border: 2px solid var(--ink); border-radius: 14px; background: var(--white); }
    .lab-guide h2 { margin-top: 0; font-size: 22px; }
    .challenge { padding: 12px 0; border-bottom: 1px solid #cbc7bb; font-size: 13px; }
    .challenge:last-child { border: 0; }
    .challenge.done { color: var(--teal); text-decoration: line-through; }
    .lab-help { margin-top: 18px; color: var(--muted); font: 11px/1.6 var(--mono); }

    .quiz-card { max-width: 780px; margin-top: 36px; padding: clamp(24px,5vw,46px); border: 2px solid var(--ink); border-radius: 16px; background: var(--white); box-shadow: 8px 8px 0 var(--ink); }
    .quiz-progress { color: var(--muted); font: 700 11px var(--mono); text-transform: uppercase; }
    .quiz-card h2 { margin: 12px 0 24px; font-size: clamp(26px,4vw,38px); line-height: 1.15; }
    .answers { display: grid; gap: 10px; }
    .answer { padding: 14px 16px; border: 2px solid var(--ink); border-radius: 10px; background: var(--paper); text-align: left; cursor: pointer; }
    .answer:hover { background: var(--paper-2); }
    .answer.correct { background: var(--lime); }
    .answer.wrong { background: #ff9b85; }
    .quiz-feedback { min-height: 50px; margin-top: 18px; font-size: 14px; }
    .quiz-result { text-align: center; }
    .score-ring { display: grid; place-items: center; width: 150px; height: 150px; margin: 10px auto 24px; border: 3px solid var(--ink); border-radius: 50%; background: var(--lime); box-shadow: 7px 7px 0 var(--ink); font: 900 38px var(--mono); }

    footer { margin-top: 70px; padding: 26px 0 0; border-top: 2px solid var(--ink); color: var(--muted); font: 12px var(--mono); }
    .toast { position: fixed; right: 20px; bottom: 20px; z-index: 80; padding: 12px 16px; border: 2px solid var(--ink); border-radius: 10px; background: var(--lime); box-shadow: 4px 4px 0 var(--ink); font: 750 12px var(--mono); transform: translateY(140%); transition: transform .25s; }
    .toast.show { transform: translateY(0); }

    @media (max-width: 1050px) {
      .top-nav { display: none; }
      .menu-btn { display: block; }
      .sidebar { transform: translateX(-105%); transition: transform .25s; box-shadow: 10px 0 30px rgba(0,0,0,.15); }
      .sidebar.open { transform: translateX(0); }
      main { margin-left: 0; }
      .progress-pill { margin-left: auto; }
      .hero { grid-template-columns: 1fr; padding-top: 30px; }
      .terminal-card { max-width: 650px; }
    }
    @media (max-width: 760px) {
      .topbar { height: 62px; padding: 0 16px; }
      .brand span:last-child { display: none; }
      .progress-pill { min-width: 126px; }
      .sidebar { top: 62px; }
      .home, .lesson-page, .tool-page { padding: 34px 18px 60px; }
      h1 { font-size: clamp(52px,19vw,78px); }
      .hero .outline { display: inline-block; max-width: 100%; font-size: clamp(38px,12vw,56px); white-space: nowrap; }
      .hero { min-width: 0; min-height: 0; }
      .hero > * { min-width: 0; }
      .terminal-card { max-width: calc(100vw - 52px); margin-inline: auto; }
      .terminal-window { min-width: 0; }
      .terminal-body { min-height: 280px; overflow: hidden; font-size: 12px; }
      .sticker { right: -8px; width: 82px; height: 82px; font-size: 10px; }
      .stats { grid-template-columns: 1fr; }
      .stat + .stat { border-left: 0; border-top: 2px solid var(--ink); }
      .section-head { display: block; }
      .section-head p { margin-top: 12px; }
      .module-grid, .command-grid { grid-template-columns: 1fr; }
      .module-card { grid-template-columns: 56px 1fr auto; padding: 16px; }
      .module-icon { width: 54px; height: 54px; }
      .principles { grid-template-columns: 1fr; }
      .lesson-hero { grid-template-columns: 1fr; }
      .lesson-badge { width: 80px; height: 80px; grid-row: 1; }
      .lesson-content { grid-template-columns: 1fr; }
      .toc { display: none; }
      .lesson-footer { align-items: stretch; flex-direction: column; }
      .lab-shell { grid-template-columns: 1fr; }
      .lab-guide { order: -1; }
    }
    @media (prefers-reduced-motion: reduce) {
      *, *::before, *::after { scroll-behavior: auto !important; animation-duration: .01ms !important; transition-duration: .01ms !important; }
    }