/* ─── design tokens — light & dark palettes ───────────────────────── */

:root {
  /* Shared */
  --mono: ui-monospace, "JetBrains Mono", "SF Mono", Menlo, Consolas, monospace;
  --sans: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
          "Helvetica Neue", Arial, sans-serif;
  --maxw: 960px;
  --maxw-wide: 1120px;
}

/* Light — sibling of contract-hero/acc-deepbook-course */
:root,
:root[data-theme="light"] {
  color-scheme: light;
  --bg: #fafaf7;
  --bg-soft: #f3f4ee;
  --surface: #ffffff;
  --surface-elev: #fbfbf8;
  --line: #e5e7eb;
  --line-soft: #efefe9;
  --text: #0f172a;
  --text-soft: #475569;
  --text-dim: #64748b;
  --accent: #0f4c75;
  --accent-strong: #0c3d5d;
  --accent-soft: #e6eef4;
  --accent-line: rgba(15, 76, 117, 0.25);
  --code-bg: #f1f5f9;
  --warn: #92400e;
  --warn-soft: #fef3c7;
  --good: #047857;
  --good-soft: #d1fae5;
  --bad: #b91c1c;
  --shadow-card: 0 1px 2px rgba(15, 23, 42, 0.03);
  --shadow-card-hover: 0 4px 12px rgba(15, 23, 42, 0.06);
}

/* Dark — sibling of mystenlabs/evm-sui */
:root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #07080b;
  --bg-soft: #0d1015;
  --surface: #11151b;
  --surface-elev: #161b22;
  --line: #1f2630;
  --line-soft: #161c25;
  --text: #e6edf3;
  --text-soft: #9aa6b2;
  /* Lightened from #5e6a78 (~3.4:1) to clear WCAG AA 4.5:1 on --bg for the
     small mono text that uses it (meta strips, tags, breadcrumbs). */
  --text-dim: #8b97a5;
  --accent: #4da2ff;
  --accent-strong: #6db5ff;
  --accent-soft: rgba(77, 162, 255, 0.12);
  --accent-line: rgba(77, 162, 255, 0.35);
  --code-bg: #0b0e13;
  --warn: #f0b429;
  --warn-soft: rgba(240, 180, 41, 0.1);
  --good: #4ade80;
  --good-soft: rgba(74, 222, 128, 0.1);
  --bad: #f87171;
  --shadow-card: 0 1px 2px rgba(0, 0, 0, 0.35);
  --shadow-card-hover: 0 6px 16px rgba(77, 162, 255, 0.06);
}

/* `data-theme` is always set on first paint by theme.js (resolves system →
   light|dark via matchMedia), so the CSS only needs the two explicit
   palette blocks above — no `@media (prefers-color-scheme: ...)` mirror. */

/* ─── reset + base ────────────────────────────────────────────────── */

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.55;
  color: var(--text);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
}

a {
  color: var(--accent);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color 120ms ease, color 120ms ease;
}
a:hover { border-bottom-color: var(--accent); }

/* Visible keyboard focus for links, the theme toggle, and any focusable. */
:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
  border-radius: 4px;
}

::selection { background: var(--accent-soft); color: var(--text); }

.wrap { max-width: var(--maxw); margin: 0 auto; padding: 0 24px; }
.wrap-wide { max-width: var(--maxw-wide); margin: 0 auto; padding: 0 24px; }

/* ─── rail / top nav ──────────────────────────────────────────────── */

header.site {
  border-bottom: 1px solid var(--line);
  background: var(--bg);
  position: sticky;
  top: 0;
  z-index: 20;
}
header.site .wrap {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 14px;
  padding-bottom: 14px;
  gap: 16px;
}
.brand {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 600;
  color: var(--text);
  letter-spacing: -0.01em;
  font-size: 15px;
  border: 0;
}
.brand:hover { border: 0; color: var(--accent); }
.brand-mark { width: 26px; height: 26px; flex: none; }

nav.site-nav {
  display: flex;
  align-items: center;
  gap: 18px;
  font-size: 14px;
}
nav.site-nav a {
  color: var(--text-soft);
  border: 0;
}
nav.site-nav a:hover { color: var(--accent); border: 0; }
nav.site-nav .crumbs {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--text-dim);
}
nav.site-nav .crumbs strong { color: var(--text-soft); font-weight: 500; }

button.theme-toggle {
  background: transparent;
  border: 1px solid var(--line);
  color: var(--text-soft);
  width: 32px;
  height: 32px;
  border-radius: 8px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: border-color 120ms ease, color 120ms ease;
}
button.theme-toggle:hover {
  border-color: var(--accent);
  color: var(--accent);
}
button.theme-toggle svg { width: 16px; height: 16px; }
/* Icon visibility tracks the active palette — dark theme shows the sun
   (click to go light), light theme shows the moon (click to go dark). */
:root[data-theme="dark"] button.theme-toggle .icon-moon,
:root[data-theme="light"] button.theme-toggle .icon-sun { display: none; }

/* ─── sections ────────────────────────────────────────────────────── */

main section { padding: 56px 0; }
main section + section { border-top: 1px solid var(--line); }

.hero {
  padding-top: 80px;
  padding-bottom: 48px;
  position: relative;
  overflow: hidden;
}
:root[data-theme="dark"] .hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background: radial-gradient(1100px 400px at 20% -10%, rgba(77, 162, 255, 0.1), transparent 60%),
              radial-gradient(800px 280px at 90% 30%, rgba(77, 162, 255, 0.05), transparent 60%);
  pointer-events: none;
}
.hero .wrap { position: relative; }

.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  background: var(--accent-soft);
  border: 1px solid var(--accent-line);
  padding: 5px 12px;
  border-radius: 999px;
  margin-bottom: 18px;
}

h1 {
  font-size: clamp(30px, 4.6vw, 46px);
  line-height: 1.1;
  letter-spacing: -0.02em;
  margin: 0 0 18px 0;
  max-width: 22ch;
  font-weight: 650;
}
h1 em {
  font-style: normal;
  color: var(--accent);
}
.lede {
  font-size: 19px;
  line-height: 1.55;
  color: var(--text-soft);
  max-width: 62ch;
  margin: 0 0 28px 0;
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  align-items: center;
}
.btn {
  display: inline-block;
  padding: 10px 18px;
  border-radius: 8px;
  font-weight: 500;
  font-size: 15px;
  border: 1px solid transparent;
  transition: background 120ms ease, border-color 120ms ease, color 120ms ease;
}
.btn:hover { border-bottom-color: transparent; }
.btn-primary {
  background: var(--accent);
  color: #fff;
}
.btn-primary:hover {
  background: var(--accent-strong);
  color: #fff;
}
/* Dark theme's Sui-blue accent is too bright for white text; flip to ink. */
:root[data-theme="dark"] .btn-primary,
:root[data-theme="dark"] .btn-primary:hover { color: #07080b; font-weight: 600; }
.btn-secondary {
  background: transparent;
  color: var(--accent);
  border-color: var(--line);
}
.btn-secondary:hover { border-color: var(--accent); }

/* Meta strip — used under headlines on per-lesson pages */
.meta {
  display: flex;
  flex-wrap: wrap;
  gap: 18px 28px;
  font-family: var(--mono);
  font-size: 12px;
  color: var(--text-dim);
  letter-spacing: 0.04em;
  margin-top: 8px;
}
.meta strong { color: var(--text-soft); font-weight: 500; margin-right: 6px; }
.meta a { color: var(--text-soft); border-bottom-color: var(--line); }
.meta a:hover { color: var(--accent); border-bottom-color: var(--accent); }

/* ─── headings + section ledes ────────────────────────────────────── */

h2 {
  font-size: clamp(22px, 2.6vw, 30px);
  letter-spacing: -0.015em;
  margin: 0 0 12px 0;
  font-weight: 600;
}
h2 + p.section-lede {
  color: var(--text-soft);
  margin: 0 0 32px 0;
  max-width: 62ch;
  font-size: 17px;
}
h3 {
  font-size: 18px;
  margin: 0 0 8px 0;
  letter-spacing: -0.01em;
  font-weight: 600;
}

/* ─── code ────────────────────────────────────────────────────────── */

pre {
  background: var(--code-bg);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 14px 16px;
  overflow-x: auto;
  font-family: var(--mono);
  font-size: 14px;
  line-height: 1.55;
  margin: 0 0 16px 0;
  color: var(--text);
}
code { font-family: var(--mono); }
p code, li code, td code {
  background: var(--code-bg);
  padding: 1px 5px;
  border-radius: 4px;
  font-size: 0.92em;
  border: 1px solid var(--line-soft);
}

/* ─── lesson tiles (landing) ──────────────────────────────────────── */

.lesson-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 16px;
  margin: 32px 0 0 0;
  padding: 0;
  list-style: none;
}
.lesson-tile {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 20px 22px;
  display: grid;
  grid-template-columns: 64px 1fr auto;
  align-items: start;
  gap: 18px;
  box-shadow: var(--shadow-card);
  transition: border-color 120ms ease, box-shadow 120ms ease, transform 120ms ease;
}
.lesson-tile:hover {
  border-color: var(--accent-line);
  box-shadow: var(--shadow-card-hover);
  transform: translateY(-1px);
}
.lesson-tile .num {
  font-family: var(--mono);
  font-size: 22px;
  font-weight: 600;
  color: var(--accent);
  letter-spacing: -0.02em;
  line-height: 1.1;
  padding-top: 3px;
}
.lesson-tile .body h3 {
  font-size: 17px;
  margin: 0 0 6px 0;
  font-weight: 600;
}
.lesson-tile .body h3 a {
  color: var(--text);
  border: 0;
}
.lesson-tile .body h3 a:hover { color: var(--accent); }
.lesson-tile .body p {
  margin: 0 0 10px 0;
  font-size: 15px;
  color: var(--text-soft);
  line-height: 1.5;
}
.lesson-tile .tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px 10px;
  font-family: var(--mono);
  font-size: 11px;
  color: var(--text-dim);
  letter-spacing: 0.04em;
  margin-top: 6px;
}
.lesson-tile .tags span {
  border: 1px solid var(--line);
  padding: 2px 8px;
  border-radius: 999px;
  background: var(--surface-elev);
}
.lesson-tile .tags span.good { color: var(--good); border-color: var(--good); background: var(--good-soft); }
.lesson-tile .links {
  display: flex;
  flex-direction: column;
  gap: 4px;
  align-items: flex-end;
  font-family: var(--mono);
  font-size: 12px;
  min-width: 140px;
}
.lesson-tile .links a {
  color: var(--text-soft);
  border-bottom-color: var(--line);
}
.lesson-tile .links a:hover { color: var(--accent); border-bottom-color: var(--accent); }
.lesson-tile .links a.primary {
  color: var(--accent);
  font-weight: 500;
}

@media (max-width: 720px) {
  .lesson-tile {
    grid-template-columns: 1fr;
    gap: 10px;
  }
  .lesson-tile .num { font-size: 18px; padding-top: 0; }
  .lesson-tile .links {
    flex-direction: row;
    flex-wrap: wrap;
    align-items: flex-start;
    gap: 10px 16px;
  }
}

/* ─── feature lists (e.g. what you'll build) ──────────────────────── */

.build-list {
  list-style: none;
  padding: 0;
  margin: 32px 0 0 0;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 12px 32px;
}
.build-list li {
  padding-left: 26px;
  position: relative;
  color: var(--text);
  font-size: 15px;
  line-height: 1.55;
}
.build-list li::before {
  content: "";
  position: absolute;
  left: 0;
  top: 9px;
  width: 14px;
  height: 8px;
  border-left: 2px solid var(--good);
  border-bottom: 2px solid var(--good);
  transform: rotate(-45deg);
}
.build-list li strong { font-weight: 600; }

@media (max-width: 720px) {
  .build-list { grid-template-columns: 1fr; }
}

/* ─── quick-start steps + trust note + details ────────────────────── */

.step {
  display: grid;
  grid-template-columns: 36px 1fr;
  gap: 16px;
  margin-bottom: 22px;
}
.step .n {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 600;
  font-size: 14px;
  display: flex;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--accent-line);
}
.step h3 {
  margin: 2px 0 6px 0;
  font-size: 16px;
}
.step p {
  margin: 0 0 8px 0;
  color: var(--text-soft);
  font-size: 15px;
}

aside.note {
  background: var(--warn-soft);
  border-left: 3px solid var(--warn);
  color: var(--text);
  padding: 14px 18px;
  border-radius: 6px;
  font-size: 15px;
  margin: 16px 0 0 0;
}
aside.note strong { color: var(--warn); }

details {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 8px;
  padding: 14px 18px;
  margin-top: 16px;
  font-size: 15px;
}
details summary {
  cursor: pointer;
  font-weight: 600;
  color: var(--accent);
}
details[open] summary { margin-bottom: 12px; }
details p { margin: 0 0 10px 0; color: var(--text-soft); }
details code { font-size: 0.92em; }

/* ─── per-lesson "what you'll write" cards ────────────────────────── */

.section-cards {
  display: grid;
  grid-template-columns: 1fr;
  gap: 14px;
  margin: 24px 0 0 0;
  padding: 0;
  list-style: none;
}
.section-cards li {
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 18px 20px;
  box-shadow: var(--shadow-card);
}
.section-cards .head {
  display: flex;
  align-items: baseline;
  gap: 12px;
  margin-bottom: 8px;
}
.section-cards .id {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--accent);
  letter-spacing: 0.04em;
  text-transform: uppercase;
  border: 1px solid var(--accent-line);
  background: var(--accent-soft);
  padding: 2px 8px;
  border-radius: 999px;
  flex: none;
}
.section-cards h3 {
  margin: 0;
  font-size: 16px;
  font-weight: 600;
}
.section-cards .key {
  color: var(--text-soft);
  font-size: 14.5px;
  line-height: 1.55;
  margin: 0;
}
.section-cards .key strong { color: var(--text); }

/* ─── verification block ──────────────────────────────────────────── */

.verify-block {
  background: var(--surface);
  border: 1px solid var(--line);
  border-left: 3px solid var(--good);
  border-radius: 8px;
  padding: 18px 22px;
  margin-top: 28px;
}
.verify-block h3 {
  color: var(--good);
  font-size: 14px;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  font-family: var(--mono);
  font-weight: 600;
  margin: 0 0 8px 0;
}
.verify-block p { margin: 0 0 8px 0; color: var(--text); font-size: 15px; }
.verify-block pre { margin: 8px 0 0 0; }

/* ─── footer ──────────────────────────────────────────────────────── */

footer.site {
  border-top: 1px solid var(--line);
  padding: 28px 0 40px 0;
  color: var(--text-soft);
  font-size: 14px;
  background: var(--bg);
}
footer.site .wrap {
  display: flex;
  flex-wrap: wrap;
  gap: 16px;
  justify-content: space-between;
  align-items: center;
}
footer.site a { color: var(--accent); border: 0; }
footer.site a:hover { border-bottom: 1px solid var(--accent); }

/* ─── flow diagram (landing) — SVG class hooks ────────────────────── */

.diagram {
  margin: 0;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 22px;
}
.diagram figcaption {
  color: var(--text-soft);
  font-size: 14px;
  margin-top: 14px;
  text-align: center;
}
.flow-svg { width: 100%; height: auto; display: block; }
.flow-svg text { font-family: var(--sans); text-anchor: middle; }
.flow-svg .box { fill: var(--surface); stroke: var(--line); stroke-width: 1; }
.flow-svg .box-accent { fill: var(--accent-soft); stroke: var(--accent); stroke-width: 1; }
.flow-svg .box-outline-accent { fill: var(--surface); stroke: var(--accent); stroke-width: 1; }
.flow-svg .box-good { fill: var(--good-soft); stroke: var(--good); stroke-width: 1; }
.flow-svg .connector { stroke: var(--text-soft); stroke-width: 1.4; fill: none; }
.flow-svg .divider { stroke: var(--line); stroke-width: 1; fill: none; }
.flow-svg .arrow-head { fill: var(--text-soft); }
.flow-svg .t { fill: var(--text); }
.flow-svg .t-soft { fill: var(--text-soft); }
.flow-svg .t-accent { fill: var(--accent); }
.flow-svg .t-good { fill: var(--good); }
.flow-svg .t-mono { font-family: var(--mono); }

/* Lesson "Sources" lists override the 2-column .build-list to stack. */
.build-list--stacked { grid-template-columns: 1fr; gap: 12px; }

/* ─── small viewports ────────────────────────────────────────────── */

@media (max-width: 720px) {
  main section { padding: 40px 0; }
  .hero { padding-top: 48px; padding-bottom: 32px; }
  nav.site-nav { gap: 12px; font-size: 13px; }
  nav.site-nav .crumbs { display: none; }
  .lede { font-size: 17px; }
}