:root {
  --ink: #13212b;
  --ink-soft: #53636e;
  --paper: #f7f4ed;
  --paper-deep: #ece7dc;
  --white: #fffdf8;
  --navy: #0c1720;
  --teal: #0f766e;
  --teal-bright: #21a89b;
  --teal-pale: #d9efea;
  --coral: #e9684b;
  --coral-pale: #fbe4dc;
  --gold: #bd7b14;
  --gold-pale: #f4e6c8;
  --line: #d8d2c6;
  --shadow: 0 16px 45px rgba(17, 34, 45, .09);
  --radius: 18px;
  --display: "Fraunces", Georgia, serif;
  --sans: "DM Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --mono: "IBM Plex Mono", monospace;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: var(--paper); color: var(--ink); font-family: var(--sans); line-height: 1.58; -webkit-font-smoothing: antialiased; }
a { color: inherit; }
button, input, textarea { font: inherit; }
button { color: inherit; }
.skip-link { position: fixed; left: 1rem; top: -5rem; z-index: 1000; background: var(--white); color: var(--navy); padding: .75rem 1rem; border-radius: 8px; }
.skip-link:focus { top: 1rem; }

.site-bar, .lesson-bar { height: 64px; padding: 0 max(1rem, calc((100vw - 1180px) / 2)); display: flex; align-items: center; justify-content: space-between; background: var(--navy); color: #fff; border-bottom: 1px solid rgba(255,255,255,.12); }
.brand { display: flex; align-items: center; gap: .7rem; text-decoration: none; font-weight: 700; letter-spacing: -.02em; }
.brand-mark { width: 32px; height: 32px; display: grid; place-items: center; border: 1px solid rgba(255,255,255,.4); border-radius: 50%; font-family: var(--display); color: #80d9cf; }
.quiet-button, .menu-button, .icon-button { border: 0; background: transparent; color: inherit; cursor: pointer; }
.quiet-button { color: #bdc8ce; font-size: .83rem; padding: .7rem; }
.quiet-button:hover, .quiet-button:focus-visible { color: #fff; }

.hero { background: var(--navy); color: #fff; padding: 4rem max(1.25rem, calc((100vw - 1180px) / 2)) 5rem; display: grid; grid-template-columns: minmax(0, 1.08fr) minmax(340px, .92fr); gap: clamp(2.5rem, 6vw, 6rem); align-items: center; overflow: hidden; position: relative; }
.hero::before { content: ""; width: 420px; height: 420px; border: 1px solid rgba(87,204,192,.15); border-radius: 50%; position: absolute; right: -190px; top: -180px; box-shadow: 0 0 0 70px rgba(87,204,192,.035), 0 0 0 140px rgba(87,204,192,.02); }
.hero-copy, .system-preview { position: relative; z-index: 1; }
.eyebrow { font-family: var(--mono); font-size: .72rem; letter-spacing: .12em; color: var(--teal); margin: 0 0 .7rem; }
.hero .eyebrow { color: #73d2c7; }
h1, h2, h3 { text-wrap: balance; }
.hero h1 { font-family: var(--display); font-size: clamp(2.65rem, 6vw, 5.25rem); line-height: .98; letter-spacing: -.045em; margin: 0; max-width: 760px; }
.hero h1 span { color: #71d0c6; }
.hero-dek { font-size: clamp(1.08rem, 2vw, 1.3rem); max-width: 610px; color: #c7d0d5; margin: 1.6rem 0 0; }
.hero-actions { display: flex; flex-wrap: wrap; gap: .8rem; margin: 2rem 0 1.4rem; }
.button { min-height: 46px; padding: .78rem 1.1rem; display: inline-flex; align-items: center; justify-content: center; gap: .45rem; border: 1px solid transparent; border-radius: 10px; text-decoration: none; font-weight: 700; cursor: pointer; transition: transform .18s ease, background .18s ease, border-color .18s ease; }
.button:hover { transform: translateY(-1px); }
.button:focus-visible, button:focus-visible, a:focus-visible { outline: 3px solid #f7bd55; outline-offset: 3px; }
.button-primary { background: var(--coral); color: #fff; }
.button-primary:hover { background: #d9583c; }
.button-secondary { background: transparent; color: currentColor; border-color: var(--line); }
.hero .button-secondary { border-color: rgba(255,255,255,.28); color: #fff; }
.hero-meta { display: flex; flex-wrap: wrap; gap: .45rem 1.6rem; list-style: none; padding: 0; margin: 0; color: #9fadb5; font-size: .86rem; }
.hero-meta li::before { content: "✓"; color: #6cd0c4; margin-right: .4rem; }

.system-preview { background: #122733; border: 1px solid rgba(118,213,201,.25); padding: 1rem; border-radius: 22px; box-shadow: 0 30px 80px rgba(0,0,0,.25); transform: rotate(1deg); }
.preview-topline { display: flex; justify-content: space-between; align-items: center; font: .63rem var(--mono); letter-spacing: .08em; color: #9cb1bb; padding: .1rem .35rem .8rem; }
.live-dot { color: #6dd2c7; }
.live-dot::before { content: ""; width: 6px; height: 6px; display: inline-block; margin-right: .4rem; background: #6dd2c7; border-radius: 50%; box-shadow: 0 0 0 4px rgba(109,210,199,.12); }
.system-stack { list-style: none; padding: 0; margin: 0; display: grid; gap: .55rem; }
.system-stack li { display: grid; grid-template-columns: 30px 1fr 24px; align-items: center; gap: .75rem; padding: .85rem; background: rgba(255,255,255,.055); border: 1px solid rgba(255,255,255,.08); border-radius: 12px; }
.stack-number { color: #6dd2c7; font: .65rem var(--mono); }
.system-stack strong, .system-stack small { display: block; }
.system-stack strong { font-size: .92rem; }
.system-stack small { color: #9eacb4; margin-top: .08rem; }
.stack-check { color: #6dd2c7; }
.preview-note { color: #9eacb4; font-size: .8rem; margin: .8rem .35rem .15rem; }


.course-section { max-width: 1180px; margin: 0 auto; padding: 5rem 1.25rem 3rem; }
.section-heading { display: flex; justify-content: space-between; gap: 2rem; align-items: end; margin-bottom: 2rem; }
.section-heading h2, .safety-banner h2 { font: 700 clamp(2rem, 4vw, 3rem)/1.08 var(--display); letter-spacing: -.035em; margin: 0; }
.progress-summary { min-width: 210px; text-align: right; color: var(--ink-soft); font-size: .78rem; }
.progress-track { height: 5px; background: #d7d1c5; border-radius: 10px; overflow: hidden; margin-top: .45rem; }
.progress-track span { display: block; width: 0; height: 100%; background: var(--teal); transition: width .35s ease; }
.phase-list { display: grid; gap: 2.2rem; }
.phase-header { display: flex; align-items: center; gap: 1rem; margin-bottom: .8rem; }
.phase-number { color: var(--teal); font: .68rem var(--mono); }
.phase-title { font-size: 1.05rem; margin: 0; }
.phase-time { color: var(--ink-soft); font-size: .76rem; margin-left: auto; }
.lesson-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: .75rem; }
.lesson-card { background: var(--white); border: 1px solid var(--line); border-radius: 14px; text-decoration: none; padding: 1rem; display: grid; grid-template-columns: 38px 1fr auto; gap: .9rem; align-items: center; transition: transform .18s ease, border-color .18s ease, box-shadow .18s ease; }
.lesson-card:hover { transform: translateY(-2px); border-color: #a8bcb8; box-shadow: 0 10px 28px rgba(17,34,45,.07); }
.lesson-card.complete { background: #f0f7f4; border-color: #b9d7d0; }
.lesson-count { width: 38px; height: 38px; display: grid; place-items: center; border-radius: 50%; background: var(--paper-deep); font: .72rem var(--mono); color: var(--ink-soft); }
.lesson-card.complete .lesson-count { background: var(--teal); color: #fff; }
.lesson-card h4 { font-size: .98rem; line-height: 1.25; margin: 0 0 .18rem; }
.lesson-card p { color: var(--ink-soft); font-size: .78rem; line-height: 1.35; margin: 0; }
.lesson-time { font: .66rem var(--mono); color: var(--ink-soft); white-space: nowrap; }
.artifact-tag { display: inline-block; color: var(--teal); font: .62rem var(--mono); margin-top: .35rem; }
.safety-banner { max-width: 1130px; margin: 2rem auto 5rem; padding: 2rem; background: var(--teal-pale); border: 1px solid #acd5cc; border-radius: var(--radius); display: grid; grid-template-columns: 68px 1fr; gap: 1.4rem; align-items: center; }
.safety-icon { width: 62px; height: 62px; display: grid; place-items: center; border-radius: 50%; border: 2px solid var(--teal); color: var(--teal); font: .8rem var(--mono); }
.safety-banner h2 { font-size: 1.65rem; }
.safety-banner p { margin: .4rem 0 0; color: #315b56; }
.site-footer { background: var(--navy); color: #aab7bd; padding: 2rem max(1.25rem, calc((100vw - 1180px) / 2)); display: flex; justify-content: space-between; gap: 1rem; }
.site-footer span { font-family: var(--display); color: #fff; }
.site-footer p { margin: 0; }

/* Lesson shell */
.lesson-bar { position: sticky; top: 0; z-index: 50; padding: 0 max(1rem, calc((100vw - 960px) / 2)); }
.back-link { color: #d5dde1; text-decoration: none; font-weight: 600; font-size: .86rem; }
.lesson-bar-progress { width: min(280px, 35vw); color: #a9b5bb; font-size: .66rem; text-align: center; }
.lesson-bar-progress .progress-track { background: rgba(255,255,255,.15); }
.lesson-bar-progress .progress-track span { background: #6bd0c4; }
.menu-button { border: 1px solid rgba(255,255,255,.25); border-radius: 8px; padding: .45rem .65rem; font-size: .78rem; }
.lesson-shell { max-width: 800px; margin: 0 auto; padding: 3.25rem 1.25rem 8rem; }
.lesson-hero { border-bottom: 1px solid var(--line); padding-bottom: 2rem; margin-bottom: 2.5rem; }
.lesson-kicker { color: var(--teal); font: .7rem var(--mono); letter-spacing: .09em; margin: 0 0 .75rem; }
.lesson-hero h1 { font: 700 clamp(2.35rem, 7vw, 4.3rem)/1.02 var(--display); letter-spacing: -.045em; margin: 0; }
.lesson-summary { color: var(--ink-soft); font-size: 1.12rem; max-width: 680px; margin: 1rem 0; }
.lesson-meta { display: flex; flex-wrap: wrap; gap: .65rem; color: var(--ink-soft); font-size: .76rem; }
.lesson-meta span { padding: .28rem .6rem; background: var(--paper-deep); border-radius: 30px; }
.lesson-section { margin: 0 0 3rem; scroll-margin-top: 90px; }
.lesson-section > h2 { font: 700 clamp(1.7rem, 4vw, 2.35rem)/1.1 var(--display); letter-spacing: -.025em; margin: 0 0 .9rem; }
.lesson-section > h3 { font-size: 1.05rem; margin-top: 1.7rem; }
.lesson-section p { margin: .7rem 0; }
.lead { font-size: 1.08rem; color: #30434e; }
.key-line { font: 600 1.25rem/1.45 var(--display); padding: 1.15rem 1.35rem; border-left: 4px solid var(--teal); background: var(--teal-pale); }
.callout, .artifact-box, .scenario, .tool-card, .model-visual, .checklist-box { border: 1px solid var(--line); border-radius: var(--radius); padding: 1.25rem; margin: 1.2rem 0; background: var(--white); }
.callout.warning { background: var(--coral-pale); border-color: #efb7a7; }
.callout.note { background: var(--gold-pale); border-color: #dec18a; }
.callout.safe { background: var(--teal-pale); border-color: #abd2ca; }
.callout-label { display: block; font: .67rem var(--mono); letter-spacing: .08em; margin-bottom: .4rem; color: var(--teal); }
.warning .callout-label { color: #b44630; }
.callout p:last-child { margin-bottom: 0; }
.plain-list, .number-list { padding-left: 1.2rem; }
.plain-list li, .number-list li { margin: .65rem 0; padding-left: .2rem; }
.definition-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: .75rem; margin: 1.2rem 0; }
.definition-card { padding: 1rem; background: var(--white); border: 1px solid var(--line); border-radius: 13px; }
.definition-card strong { display: block; color: var(--teal); margin-bottom: .25rem; }
.definition-card p { color: var(--ink-soft); font-size: .88rem; margin: 0; }

.model-visual { display: grid; gap: .7rem; background: var(--navy); color: #fff; padding: 1rem; }
.token-row { display: flex; flex-wrap: wrap; gap: .35rem; }
.token { padding: .35rem .5rem; border-radius: 6px; background: rgba(111,210,199,.13); color: #91e0d6; font: .7rem var(--mono); border: 1px solid rgba(111,210,199,.22); }
.next-token { display: grid; grid-template-columns: 1fr auto; align-items: center; gap: .6rem; padding: .6rem .75rem; background: rgba(255,255,255,.055); border-radius: 8px; }
.next-token span:last-child { color: #8edbd2; font: .7rem var(--mono); }
.flow { display: grid; grid-template-columns: 1fr auto 1fr auto 1fr; gap: .5rem; align-items: stretch; margin: 1.2rem 0; }
.flow-step { padding: .8rem; background: var(--white); border: 1px solid var(--line); border-radius: 10px; font-size: .82rem; text-align: center; }
.flow-arrow { align-self: center; color: var(--coral); }

.scenario { background: #f3eee4; }
.scenario-label { font: .67rem var(--mono); color: var(--gold); letter-spacing: .08em; }
.scenario h3 { font-size: 1.05rem; margin: .45rem 0; }
.scenario-options { display: grid; gap: .5rem; margin-top: .9rem; }
.scenario-option { width: 100%; text-align: left; padding: .75rem .85rem; background: var(--white); border: 1px solid var(--line); border-radius: 9px; cursor: pointer; }
.scenario-option:hover { border-color: var(--teal); }
.scenario-option.selected { border-color: var(--teal); box-shadow: inset 3px 0 var(--teal); }
.scenario-feedback { display: none; margin: .8rem 0 0; padding: .8rem; border-radius: 9px; background: var(--teal-pale); }
.scenario-feedback.visible { display: block; }

.artifact-box { padding: 0; overflow: hidden; border-color: #9ecbc3; }
.artifact-header { background: var(--teal); color: #fff; padding: .85rem 1rem; display: flex; justify-content: space-between; align-items: center; gap: 1rem; }
.artifact-header span { font: .68rem var(--mono); letter-spacing: .08em; }
.artifact-body { padding: 1rem; }
.artifact-body textarea { width: 100%; min-height: 260px; resize: vertical; border: 1px solid var(--line); border-radius: 10px; background: #fffefb; color: var(--ink); padding: .9rem; font: .8rem/1.55 var(--mono); }
.artifact-actions { display: flex; flex-wrap: wrap; gap: .55rem; margin-top: .75rem; }
.small-button { border: 1px solid #8eaaa5; border-radius: 8px; background: var(--white); color: var(--teal); padding: .55rem .75rem; font-size: .78rem; font-weight: 700; cursor: pointer; }
.small-button:hover { background: var(--teal-pale); }
.checklist-box label { display: flex; gap: .65rem; align-items: flex-start; padding: .55rem 0; border-bottom: 1px solid #e5dfd4; }
.checklist-box label:last-child { border: 0; }
.checklist-box input { width: 19px; height: 19px; accent-color: var(--teal); flex: 0 0 auto; margin-top: .12rem; }
.tool-card { display: grid; grid-template-columns: 42px 1fr; gap: 1rem; }
.tool-icon { width: 42px; height: 42px; display: grid; place-items: center; border-radius: 10px; background: var(--navy); color: #7ad3c9; font: .68rem var(--mono); }
.tool-card h3 { margin: 0 0 .25rem; }
.tool-card p { color: var(--ink-soft); font-size: .88rem; margin: .25rem 0; }
.tool-card a { color: var(--teal); font-weight: 700; }
.comparison { width: 100%; border-collapse: collapse; margin: 1rem 0; font-size: .86rem; }
.comparison th, .comparison td { text-align: left; vertical-align: top; border-bottom: 1px solid var(--line); padding: .7rem .55rem; }
.comparison th { font: .67rem var(--mono); color: var(--teal); }
.code-block { overflow-x: auto; background: var(--navy); color: #d7e5e9; border-radius: 12px; padding: 1rem; font: .78rem/1.6 var(--mono); white-space: pre-wrap; }
.source-links { display: grid; gap: .55rem; padding: 0; list-style: none; }
.source-links a { display: block; padding: .7rem .8rem; background: var(--white); border: 1px solid var(--line); border-radius: 9px; color: var(--teal); text-decoration: none; font-weight: 700; }
.source-links small { display: block; color: var(--ink-soft); font-weight: 400; }
.completion-panel { background: var(--navy); color: #fff; border-radius: var(--radius); padding: 1.35rem; }
.completion-panel h2 { margin: 0 0 .35rem; font: 700 1.7rem var(--display); }
.completion-panel p { margin: 0; color: #bbc6cb; }

.lesson-nav { position: fixed; z-index: 40; left: 0; right: 0; bottom: 0; display: grid; grid-template-columns: 1fr minmax(150px, auto) 1fr; gap: .6rem; padding: .7rem max(1rem, calc((100vw - 800px) / 2)); background: rgba(247,244,237,.95); border-top: 1px solid var(--line); backdrop-filter: blur(12px); }
.lesson-nav .button:first-child { justify-self: start; }
.lesson-nav .button:last-child { justify-self: end; }
.lesson-nav .button.complete { background: var(--teal); }

.course-drawer { position: fixed; inset: 0; z-index: 100; visibility: hidden; }
.course-drawer.open { visibility: visible; }
.drawer-scrim { position: absolute; inset: 0; border: 0; background: rgba(5,12,17,.68); opacity: 0; transition: opacity .2s; }
.open .drawer-scrim { opacity: 1; }
.drawer-panel { position: absolute; top: 0; right: 0; bottom: 0; width: min(410px, 92vw); background: var(--paper); transform: translateX(100%); transition: transform .24s ease; overflow-y: auto; box-shadow: -20px 0 60px rgba(0,0,0,.2); }
.open .drawer-panel { transform: translateX(0); }
.drawer-header { height: 64px; display: flex; align-items: center; justify-content: space-between; padding: 0 1rem; background: var(--navy); color: #fff; }
.icon-button { font-size: 1.7rem; }
#drawer-lessons { padding: .7rem; }
.drawer-link { display: grid; grid-template-columns: 28px 1fr; gap: .7rem; text-decoration: none; padding: .75rem; border-radius: 9px; font-size: .86rem; }
.drawer-link:hover, .drawer-link.current { background: var(--teal-pale); }
.drawer-link.complete .drawer-number { background: var(--teal); color: #fff; }
.drawer-number { width: 28px; height: 28px; display: grid; place-items: center; background: var(--paper-deep); border-radius: 50%; font: .62rem var(--mono); }
.toast { position: fixed; left: 50%; bottom: 84px; z-index: 200; transform: translate(-50%, 12px); opacity: 0; pointer-events: none; background: var(--navy); color: #fff; padding: .7rem 1rem; border-radius: 9px; font-size: .82rem; transition: .2s ease; }
.toast.visible { transform: translate(-50%, 0); opacity: 1; }

@media (max-width: 760px) {
  .hero { grid-template-columns: 1fr; padding-top: 2.7rem; }
  .system-preview { transform: none; }
  .section-heading { display: block; }
  .progress-summary { text-align: left; margin-top: 1rem; }
  .lesson-grid { grid-template-columns: 1fr; }
  .safety-banner { margin: 1.5rem 1.25rem 4rem; grid-template-columns: 1fr; }
  .definition-grid { grid-template-columns: 1fr; }
  .flow { grid-template-columns: 1fr; }
  .flow-arrow { transform: rotate(90deg); justify-self: center; }
  .lesson-bar-progress { display: none; }
  .site-footer { display: block; }
  .site-footer p { margin-top: .35rem; }
}

@media (max-width: 540px) {
  .hero h1 { font-size: 2.75rem; }
  .hero-actions .button { width: 100%; }
  .hero-meta { display: grid; gap: .35rem; }
  .system-preview { margin-inline: -.3rem; }
  .preview-topline { align-items: start; gap: .5rem; }
  .section-heading h2 { font-size: 2rem; }
  .phase-header { flex-wrap: wrap; gap: .4rem .8rem; }
  .phase-title { flex: 1; }
  .phase-time { width: 100%; margin-left: 2.3rem; }
  .lesson-card { grid-template-columns: 34px 1fr; }
  .lesson-time { grid-column: 2; }
  .lesson-shell { padding-top: 2.1rem; }
  .lesson-hero h1 { font-size: 2.55rem; }
  .artifact-header { display: block; }
  .artifact-header .small-button { margin-top: .5rem; }
  .lesson-nav { grid-template-columns: 1fr 1fr; }
  .lesson-nav .button { padding-inline: .65rem; font-size: .78rem; }
  #complete-lesson { grid-column: 1 / -1; grid-row: 1; }
  #previous-lesson, #next-lesson { grid-row: 2; }
  .toast { bottom: 132px; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; transition: none !important; animation: none !important; }
}