/* =============================================================
   Learning Lab website
   Two registers, taken from design.md §13.2:
     story mode  paper, ink, oxblood, Spectral, 2px corners, slow
     lab mode    near-black, cyan, Inter + JetBrains Mono, 6px corners, quick
   The seam between them echoes the app's signature transition.
   Shares nothing with the skyrock.agency site.
   ============================================================= */

:root {
  /* story mode */
  --paper: #f4efe6;
  --paper-deep: #ebe4d7;
  --rule: #d8cdb9;
  --ink: #1c1917;
  --ink-soft: #57534e;
  --oxblood: #7c2d12;

  /* lab mode */
  --lab: #0f1115;
  --lab-raise: #171a21;
  --lab-line: #272b35;
  --lab-text: #e7e5e4;
  --lab-muted: #a8a29e;
  --cyan: #22d3ee;
  --ok: #34d399;

  --serif: 'Spectral', Georgia, 'Times New Roman', serif;
  --sans: 'Inter', 'Segoe UI', Arial, sans-serif;
  --mono: 'JetBrains Mono', Consolas, 'Courier New', monospace;

  --container: 1120px;
  --slow: 240ms ease;
  --quick: 120ms ease;
}

/* ---------- Base ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--serif);
  font-size: 18px;
  line-height: 1.6;
}
img { max-width: 100%; height: auto; display: block; }
p { margin: 0 0 1em; }
h1, h2, h3 { margin: 0 0 0.5em; line-height: 1.15; }
cite { font-style: italic; }
section { scroll-margin-top: 72px; }

.container { width: 100%; max-width: var(--container); margin: 0 auto; padding-inline: 20px; }
.narrow { max-width: 720px; }
.section { padding: 88px 0; }

.skip-link {
  position: absolute; left: 16px; top: -60px; z-index: 1000;
  background: var(--ink); color: var(--paper); padding: 8px 14px;
  font-family: var(--sans); font-weight: 600; text-decoration: none; border-radius: 2px;
}
.skip-link:focus { top: 12px; }

.eyebrow {
  font-family: var(--sans); font-size: 13px; font-weight: 600;
  letter-spacing: 0.14em; text-transform: uppercase; color: var(--oxblood);
  margin-bottom: 14px;
}
.big { font-size: clamp(19px, 2.2vw, 22px); line-height: 1.55; }

/* ---------- Buttons and links ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  font-family: var(--sans); font-weight: 600; font-size: 16px; line-height: 1.2;
  text-decoration: none; border: 1.5px solid transparent; border-radius: 2px;
  padding: 12px 22px; cursor: pointer;
  transition: background-color var(--slow), color var(--slow), border-color var(--slow);
}
.btn-lg { padding: 15px 28px; font-size: 17px; }
.btn-sm { padding: 8px 16px; font-size: 14px; }
.btn-ink { background: var(--ink); color: var(--paper); }
.btn-ink:hover, .btn-ink:focus-visible { background: var(--oxblood); }

.text-link {
  font-family: var(--sans); font-weight: 600; font-size: 16px;
  color: inherit; text-decoration: underline; text-decoration-thickness: 1.5px;
  text-underline-offset: 4px; text-decoration-color: var(--oxblood);
}
.text-link:hover, .text-link:focus-visible { color: var(--oxblood); }

:focus-visible { outline: 2px solid var(--oxblood); outline-offset: 3px; }
.lab :focus-visible, .site-footer :focus-visible { outline-color: var(--cyan); }

/* ---------- Header ---------- */
.site-header {
  position: sticky; top: 0; z-index: 100;
  background: rgba(244, 239, 230, 0.94);
  -webkit-backdrop-filter: blur(6px); backdrop-filter: blur(6px);
  border-bottom: 1px solid var(--rule);
}
.header-inner { display: flex; align-items: center; justify-content: space-between; gap: 16px; min-height: 64px; position: relative; }
.brand { display: flex; align-items: center; gap: 10px; text-decoration: none; color: var(--ink); }
.brand img { width: 36px; height: 36px; }
.brand span { font-family: var(--serif); font-weight: 600; font-size: 21px; }
.site-nav { display: flex; align-items: center; gap: 26px; }
.site-nav > a:not(.btn) {
  font-family: var(--sans); font-size: 14px; font-weight: 500; color: var(--ink-soft);
  text-decoration: none; transition: color var(--slow);
}
.site-nav > a:not(.btn):hover, .site-nav > a:not(.btn):focus-visible { color: var(--oxblood); }

.nav-toggle {
  display: none; flex-direction: column; justify-content: center; gap: 5px;
  width: 44px; height: 44px; padding: 10px; background: none; border: 0; cursor: pointer;
}
.nav-toggle span { display: block; height: 2px; background: var(--ink); }

@media (max-width: 760px) {
  .nav-toggle { display: flex; }
  .site-nav {
    display: none; position: absolute; top: 100%; left: -20px; right: -20px;
    flex-direction: column; align-items: stretch; gap: 0;
    background: var(--paper); border-bottom: 1px solid var(--rule); padding: 6px 20px 18px;
  }
  .site-nav.open { display: flex; }
  .site-nav > a:not(.btn) { padding: 13px 0; border-bottom: 1px solid var(--rule); font-size: 16px; }
  .site-nav .btn { margin-top: 14px; }
}

/* ---------- Hero ---------- */
.hero { padding: 72px 0 32px; }
.hero-grid { display: grid; grid-template-columns: 1.05fr 0.95fr; gap: 56px; align-items: center; }
.hero h1 { font-weight: 600; font-size: clamp(36px, 5.2vw, 58px); letter-spacing: -0.01em; }
.lede { font-size: clamp(20px, 2.3vw, 24px); line-height: 1.5; max-width: 32em; }
.lede em { color: var(--oxblood); }
.hero-actions { display: flex; flex-wrap: wrap; align-items: center; gap: 20px 28px; margin: 30px 0 18px; }
.hero-meta { font-family: var(--sans); font-size: 14px; color: var(--ink-soft); margin: 0; }

.plate { margin: 0; background: var(--paper-deep); border: 1px solid var(--ink); padding: 10px; box-shadow: 8px 8px 0 var(--rule); }
.plate img { border: 1px solid var(--rule); }
.plate figcaption { margin-top: 10px; font-size: 15px; font-variant: small-caps; letter-spacing: 0.04em; color: var(--ink-soft); text-align: center; }
.plate figcaption span { font-variant: normal; font-style: italic; letter-spacing: 0; }

@media (max-width: 860px) {
  .hero { padding-top: 48px; }
  .hero-grid { grid-template-columns: 1fr; gap: 40px; }
  .plate { max-width: 520px; }
}

/* ---------- Story sections ---------- */
.paper { background: var(--paper); color: var(--ink); }
.paper h2 { font-weight: 600; font-size: clamp(30px, 4vw, 44px); letter-spacing: -0.01em; }

.principles { display: grid; grid-template-columns: repeat(4, 1fr); gap: 28px; margin-top: 48px; }
.principles article { border-top: 2px solid var(--oxblood); padding-top: 18px; }
.principles h3 { font-weight: 600; font-size: 20px; }
.principles p { font-size: 17px; color: var(--ink-soft); margin: 0; }
@media (max-width: 980px) { .principles { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 560px) { .principles { grid-template-columns: 1fr; } }

.modules { list-style: none; padding: 0; margin: 44px 0 0; display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.modules li {
  position: relative; background: var(--paper-deep); border: 1px solid var(--rule); border-radius: 2px;
  padding: 22px 22px 50px;
}
.modules .num { font-family: var(--mono); font-size: 13px; color: var(--oxblood); }
.modules h3 { font-weight: 600; font-size: 22px; margin: 6px 0 4px; }
.modules .after { font-style: italic; color: var(--ink-soft); font-size: 16px; margin-bottom: 10px; }
.modules p { font-size: 16px; margin: 0; }
.modules .hrs { position: absolute; left: 22px; bottom: 18px; font-family: var(--mono); font-size: 13px; color: var(--ink-soft); }
@media (max-width: 900px) { .modules { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 560px) { .modules { grid-template-columns: 1fr; } }

.skyrock-links { display: flex; flex-wrap: wrap; gap: 14px 28px; margin: 26px 0 0; }

/* ---------- The seam between registers ---------- */
.seam { height: 96px; }
.seam-down { background: linear-gradient(180deg, var(--paper) 0%, var(--lab) 100%); }
.seam-up { background: linear-gradient(180deg, var(--lab) 0%, var(--paper) 100%); }

/* ---------- Lab sections ---------- */
.lab { background: var(--lab); color: var(--lab-text); font-family: var(--sans); font-size: 17px; }
.lab .eyebrow { font-family: var(--mono); font-weight: 500; letter-spacing: 0.08em; color: var(--cyan); }
.lab h2 { font-family: var(--sans); font-weight: 700; font-size: clamp(28px, 3.8vw, 40px); letter-spacing: -0.02em; color: #fff; }
.lab h3 { font-family: var(--sans); font-weight: 600; font-size: 18px; color: #fff; }
.lab .big { font-family: var(--sans); color: var(--lab-muted); }

.learn-head { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: flex-end; gap: 16px 40px; }
.source { font-family: var(--serif); font-style: italic; color: var(--lab-muted); margin: 0; }
.stats { font-family: var(--mono); font-size: 14px; color: var(--lab-muted); margin: 0; }

.token-strip { display: flex; flex-wrap: wrap; gap: 6px; margin: 40px 0 36px; font-family: var(--mono); font-size: 18px; }
.token-strip span {
  white-space: pre; padding: 6px 10px; border: 1px solid rgba(34, 211, 238, 0.55);
  border-radius: 6px; background: rgba(34, 211, 238, 0.08); color: var(--lab-text);
}
.js .token-strip span { opacity: 0; transform: translateY(6px); transition: opacity var(--quick), transform var(--quick); }
.js .token-strip.in-view span { opacity: 1; transform: none; }
.js .token-strip.in-view span:nth-child(2) { transition-delay: 160ms; }
.js .token-strip.in-view span:nth-child(3) { transition-delay: 320ms; }
.js .token-strip.in-view span:nth-child(4) { transition-delay: 480ms; }
.js .token-strip.in-view span:nth-child(5) { transition-delay: 640ms; }

.chapters { list-style: none; padding: 0; margin: 0; border-top: 1px solid var(--lab-line); }
.chapters li {
  display: grid; grid-template-columns: 64px 1fr auto; gap: 8px 20px; align-items: center;
  padding: 16px 0; border-bottom: 1px solid var(--lab-line);
}
.chapters .ch { font-family: var(--mono); font-size: 13px; color: var(--lab-muted); }
.chapters p { margin: 0; }
.chapters strong { color: #fff; }
.skill {
  font-family: var(--mono); font-size: 13px; color: var(--cyan); white-space: nowrap;
  border: 1px solid rgba(34, 211, 238, 0.5); border-radius: 6px; padding: 4px 10px;
}
.skill-quiet { color: var(--lab-muted); border-color: var(--lab-line); }
@media (max-width: 680px) {
  .chapters li { grid-template-columns: 48px 1fr; }
  .chapters .skill { grid-column: 2; justify-self: start; white-space: normal; }
}

.features { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; margin-top: 44px; }
.features article { background: var(--lab-raise); border: 1px solid var(--lab-line); border-radius: 6px; padding: 22px; }
.features p { color: var(--lab-muted); font-size: 16px; margin: 0; }
@media (max-width: 860px) { .features { grid-template-columns: 1fr; } }

.cliffhanger { padding-top: 24px; text-align: center; }
.cliffhanger blockquote { margin: 0 auto; max-width: 640px; font-family: var(--serif); font-size: clamp(21px, 2.6vw, 27px); line-height: 1.5; }
.cliffhanger blockquote p { margin: 0 0 6px; }
.cliffhanger strong { color: #fff; }
.cliffhanger .coming {
  display: inline-block; margin: 24px 0 0; font-family: var(--mono); font-size: 13px;
  letter-spacing: 0.12em; text-transform: uppercase; color: var(--cyan);
}

.downloads { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; margin-top: 36px; }
.download {
  position: relative; display: flex; flex-direction: column; gap: 4px;
  background: var(--lab-raise); border: 1px solid var(--lab-line); border-radius: 6px;
  padding: 22px 20px; text-decoration: none; color: var(--lab-text);
  transition: border-color var(--quick), transform var(--quick);
}
a.download:hover, a.download:focus-visible { border-color: var(--cyan); transform: translateY(-2px); }
.download .os { font-weight: 600; font-size: 20px; color: #fff; }
.download .detail { color: var(--lab-muted); font-size: 15px; }
.download .file { font-family: var(--mono); font-size: 13px; color: var(--cyan); margin-top: 10px; }
.download.is-recommended { border-color: var(--cyan); }
.download.is-recommended::before {
  content: "For this computer"; position: absolute; top: -11px; left: 16px;
  font-family: var(--mono); font-size: 11px; letter-spacing: 0.06em; text-transform: uppercase;
  background: var(--cyan); color: var(--lab); padding: 3px 8px; border-radius: 4px;
}
.mobile-note, .soon-note { font-family: var(--sans); color: var(--cyan); margin-top: 18px; }
@media (max-width: 900px) { .downloads { grid-template-columns: repeat(2, 1fr); row-gap: 24px; } }
@media (max-width: 480px) { .downloads { grid-template-columns: 1fr; } }

/* ---------- Footer ---------- */
.site-footer { background: var(--lab); color: var(--lab-muted); font-family: var(--sans); font-size: 14px; padding: 40px 0 36px; border-top: 1px solid var(--lab-line); }
.footer-inner { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 16px 32px; }
.footer-brand { display: flex; align-items: center; gap: 10px; margin: 0; color: var(--lab-text); font-family: var(--serif); font-weight: 600; font-size: 17px; }
.footer-nav { display: flex; flex-wrap: wrap; gap: 10px 22px; }
.footer-nav a { color: var(--lab-muted); text-decoration: none; }
.footer-nav a:hover, .footer-nav a:focus-visible { color: var(--cyan); }
.copyright { width: 100%; margin: 8px 0 0; padding-top: 18px; border-top: 1px solid var(--lab-line); }

/* ---------- Plain pages: thank-you, legal, 404 ---------- */
.page { padding: 64px 0 88px; }
.page h1 { font-weight: 600; font-size: clamp(32px, 4.6vw, 48px); letter-spacing: -0.01em; }
.page h2 { font-weight: 600; font-size: 24px; margin-top: 1.8em; }
.page ul, .page ol { padding-left: 1.3em; }
.page li { margin-bottom: 0.5em; }
.page a { color: var(--oxblood); text-underline-offset: 3px; }
.page .updated { font-family: var(--sans); font-size: 14px; color: var(--ink-soft); }
.draft-banner {
  font-family: var(--sans); font-size: 15px; background: #fff7e6; border: 1px solid #e3c98f;
  border-left: 4px solid var(--oxblood); border-radius: 2px; padding: 12px 16px; margin: 0 0 32px;
}
.steps { counter-reset: step; list-style: none; padding: 0 !important; }
.steps li { counter-increment: step; position: relative; padding-left: 48px; margin-bottom: 20px; }
.steps li::before {
  content: counter(step); position: absolute; left: 0; top: 0;
  width: 32px; height: 32px; border-radius: 50%; background: var(--ink); color: var(--paper);
  font-family: var(--sans); font-weight: 600; font-size: 15px; display: grid; place-items: center;
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .js .token-strip span { opacity: 1; transform: none; transition: none; }
  .btn, .download { transition: none; }
}