/* ===================================================================
   Esiur — design tokens
   =================================================================== */
:root {
  --bg: #fbfaf8;
  --surface: #ffffff;
  --surface-alt: #f3f1ec;
  --ink: #191714;
  --ink-soft: #5b564d;
  --ink-faint: #8a8378;
  --border: #e5e1d8;
  --teal: #0c7a72;
  --teal-dark: #085f59;
  --teal-tint: #e3f3f1;
  --amber: #b85c0d;
  --amber-tint: #fbead9;
  --red: #b3261e;
  --red-tint: #fbe9e7;
  --code-bg: #171512;
  --code-ink: #f1ede4;
  --code-border: #2c2822;

  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, Helvetica, Arial, sans-serif;
  --font-mono: ui-monospace, "Cascadia Code", "JetBrains Mono", Menlo, Consolas, "Liberation Mono", monospace;

  --radius: 10px;
  --radius-sm: 6px;
  --shadow: 0 1px 2px rgba(25, 23, 20, 0.04), 0 8px 24px rgba(25, 23, 20, 0.06);
  --max: 1120px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #14120f;
    --surface: #1b1815;
    --surface-alt: #211e19;
    --ink: #f3efe7;
    --ink-soft: #b3ac9e;
    --ink-faint: #7d766a;
    --border: #332e27;
    --teal: #35c9ba;
    --teal-dark: #7fe0d4;
    --teal-tint: #163330;
    --amber: #f0a446;
    --amber-tint: #3a2a15;
    --red: #f28b83;
    --red-tint: #3a1e1c;
    --code-bg: #0e0d0b;
    --code-ink: #e8e3d8;
    --code-border: #2a2620;
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.2), 0 8px 24px rgba(0, 0, 0, 0.35);
  }
}

/* ===================================================================
   Reset & base
   =================================================================== */
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}
img, svg { max-width: 100%; display: block; }
a { color: var(--teal-dark); text-decoration: none; }
a:hover { text-decoration: underline; }
h1, h2, h3, h4 { line-height: 1.25; font-weight: 650; letter-spacing: -0.01em; }
p { margin: 0 0 1em; color: var(--ink-soft); }
ul, ol { color: var(--ink-soft); }
code, pre, kbd { font-family: var(--font-mono); }

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

/* ===================================================================
   Nav
   =================================================================== */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 40;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border);
}
.site-nav .inner {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0 24px;
  height: 64px;
  display: flex;
  align-items: center;
  justify-content: space-between;
}
.brand {
  display: inline-flex;
  align-items: baseline;
  gap: 2px;
  font-family: var(--font-mono);
  font-size: 1.15rem;
  font-weight: 600;
  color: var(--ink);
}
.brand:hover { text-decoration: none; }
.brand .dot { color: var(--teal); }
.brand .tld { color: var(--ink-faint); font-weight: 500; }

.nav-links { display: flex; align-items: center; gap: 28px; }
.nav-links a {
  color: var(--ink-soft);
  font-size: 0.94rem;
  font-weight: 500;
  padding: 6px 0;
  border-bottom: 2px solid transparent;
}
.nav-links a:hover { color: var(--ink); text-decoration: none; }
.nav-links a.active { color: var(--ink); border-bottom-color: var(--teal); }
.nav-links a.ext { color: var(--ink-soft); }
.nav-menu-toggle {
  display: none;
  background: none;
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  width: 38px; height: 38px;
  font-size: 1.1rem;
  color: var(--ink);
  cursor: pointer;
}

@media (max-width: 760px) {
  .nav-menu-toggle { display: inline-flex; align-items: center; justify-content: center; }
  .nav-links {
    position: absolute;
    top: 64px; left: 0; right: 0;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    align-items: flex-start;
    gap: 0;
    padding: 8px 24px 16px;
    display: none;
  }
  .nav-links.open { display: flex; }
  .nav-links a { width: 100%; padding: 10px 0; border-bottom: 1px solid var(--border); }
  .nav-links a.active { border-bottom-color: var(--border); }
}

/* ===================================================================
   Buttons
   =================================================================== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 11px 20px;
  border-radius: var(--radius-sm);
  font-size: 0.92rem;
  font-weight: 600;
  border: 1px solid transparent;
  cursor: pointer;
}
.btn:hover { text-decoration: none; }
.btn-primary { background: var(--teal); color: #fff; }
.btn-primary:hover { background: var(--teal-dark); }
.btn-ghost { background: transparent; color: var(--ink); border-color: var(--border); }
.btn-ghost:hover { border-color: var(--ink-faint); background: var(--surface-alt); }
.btn-row { display: flex; gap: 12px; flex-wrap: wrap; }

/* ===================================================================
   Hero
   =================================================================== */
.hero {
  padding: 88px 0 64px;
  text-align: center;
}
.hero .eyebrow {
  display: inline-block;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: var(--teal-dark);
  background: var(--teal-tint);
  border-radius: 999px;
  padding: 5px 14px;
  margin-bottom: 20px;
  letter-spacing: 0.02em;
}
.hero h1 {
  font-size: clamp(2.1rem, 5vw, 3.4rem);
  margin: 0 0 18px;
  max-width: 18ch;
  margin-inline: auto;
}
.hero .lead {
  font-size: 1.15rem;
  color: var(--ink-soft);
  max-width: 56ch;
  margin: 0 auto 32px;
}
.hero .btn-row { justify-content: center; }

/* ===================================================================
   Sections & prose
   =================================================================== */
.section { padding: 64px 0; }
.section-head { max-width: 60ch; margin-bottom: 36px; }
.section-head.center { margin-inline: auto; text-align: center; }
.section-head h2 { font-size: 1.75rem; margin: 0 0 10px; }
.section-head p { margin: 0; }
.kicker {
  font-family: var(--font-mono);
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--teal-dark);
  font-weight: 600;
  margin-bottom: 10px;
  display: block;
}

.prose h2 { font-size: 1.5rem; margin: 2.4em 0 0.6em; padding-top: 0.2em; border-top: 1px solid var(--border); }
.prose h2:first-child { border-top: none; margin-top: 0; }
.prose h3 { font-size: 1.12rem; margin: 1.8em 0 0.6em; color: var(--ink); }
.prose p, .prose li { font-size: 0.98rem; }
.prose ul, .prose ol { padding-left: 1.3em; line-height: 1.85; }
.prose a { text-decoration: underline; text-decoration-color: var(--border); text-underline-offset: 3px; }
.prose strong { color: var(--ink); }

/* ===================================================================
   Cards
   =================================================================== */
.grid { display: grid; gap: 20px; }
.grid-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.grid-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
@media (max-width: 860px) { .grid-3 { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
@media (max-width: 640px) { .grid-3, .grid-2 { grid-template-columns: minmax(0, 1fr); } }

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  min-width: 0;
}
.feature-card h3 {
  font-size: 1rem;
  margin: 12px 0 8px;
  display: flex;
  align-items: center;
  gap: 10px;
}
.feature-card p { font-size: 0.9rem; margin: 0; }
.feature-icon {
  width: 34px; height: 34px;
  display: inline-flex; align-items: center; justify-content: center;
  border-radius: 8px;
  background: var(--teal-tint);
  color: var(--teal-dark);
  flex-shrink: 0;
}

.platform-card {
  padding: 32px;
  display: flex;
  flex-direction: column;
  gap: 14px;
  box-shadow: var(--shadow);
}
.platform-card .tag {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--teal-dark);
  background: var(--teal-tint);
  border-radius: 999px;
  padding: 3px 10px;
  width: fit-content;
}
.platform-card h3 { font-size: 1.3rem; margin: 0; }
.platform-card p { font-size: 0.92rem; margin: 0; }
.platform-card .spacer { flex: 1; }

/* ===================================================================
   Code blocks
   =================================================================== */
.code-block {
  position: relative;
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: var(--radius);
  overflow: hidden;
  margin: 16px 0;
}
.code-block pre {
  margin: 0;
  padding: 18px 20px;
  overflow-x: auto;
  font-size: 0.83rem;
  line-height: 1.65;
  color: var(--code-ink);
}
.code-block .lang {
  position: absolute;
  top: 10px; right: 14px;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: #8a8378;
}
.copy-btn {
  position: absolute;
  top: 8px; right: 8px;
  background: rgba(255,255,255,0.06);
  border: 1px solid var(--code-border);
  color: var(--code-ink);
  font-family: var(--font-sans);
  font-size: 0.72rem;
  border-radius: var(--radius-sm);
  padding: 5px 9px;
  cursor: pointer;
  opacity: 0;
  transition: opacity .12s;
}
.code-block:hover .copy-btn { opacity: 1; }
.copy-btn:hover { background: rgba(255,255,255,0.14); }

p code, li code, td code {
  background: var(--surface-alt);
  border: 1px solid var(--border);
  border-radius: 4px;
  padding: 0.12em 0.4em;
  font-size: 0.86em;
  color: var(--ink);
}

/* ===================================================================
   Callouts
   =================================================================== */
.callout {
  border-radius: var(--radius);
  border: 1px solid var(--border);
  border-left: 3px solid var(--ink-faint);
  background: var(--surface-alt);
  padding: 14px 18px;
  margin: 18px 0;
  font-size: 0.9rem;
  color: var(--ink-soft);
}
.callout strong { color: var(--ink); }
.callout-info { border-left-color: var(--teal); background: var(--teal-tint); }
.callout-warn { border-left-color: var(--amber); background: var(--amber-tint); }
.callout-danger { border-left-color: var(--red); background: var(--red-tint); }

/* ===================================================================
   Tables
   =================================================================== */
table { border-collapse: collapse; width: 100%; margin: 16px 0; font-size: 0.87rem; }
th, td { border: 1px solid var(--border); padding: 8px 12px; text-align: left; vertical-align: top; }
th { background: var(--surface-alt); font-weight: 600; color: var(--ink); }
tbody tr:nth-child(even) td { background: color-mix(in srgb, var(--surface-alt) 45%, transparent); }
.hex { font-family: var(--font-mono); font-weight: 600; color: var(--amber); }
table.compact td, table.compact th { padding: 6px 10px; font-size: 0.82rem; }

/* bit diagrams */
.bit-diagram { font-family: var(--font-mono); font-size: 0.76rem; text-align: center; }
.bit-diagram th { background: var(--code-bg); color: var(--code-ink); }
.bit-diagram td small { display: block; color: var(--ink-faint); font-size: 0.68rem; margin-top: 2px; font-family: var(--font-sans); }
.bd-a { background: color-mix(in srgb, var(--teal-tint) 80%, transparent); }
.bd-b { background: color-mix(in srgb, var(--amber-tint) 80%, transparent); }
.bd-c { background: var(--surface-alt); }

/* wire boxes: hand-annotated byte layouts */
.wire-box {
  background: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: var(--radius);
  padding: 18px 20px;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  color: #9b958a;
  overflow-x: auto;
  margin: 16px 0;
  line-height: 1.7;
  white-space: pre;
}
.wire-box .wb { color: #f0a446; font-weight: 600; } /* byte value */
.wire-box .wf { color: #35c9ba; }                    /* field name */
.wire-box .wc { color: #726c60; font-style: italic; } /* comment */

/* ===================================================================
   Protocol doc layout (sidebar + article)
   =================================================================== */
.doc-layout {
  display: grid;
  grid-template-columns: 230px 1fr;
  gap: 56px;
  align-items: start;
  padding: 48px 0 96px;
}
.doc-sidebar { position: sticky; top: 84px; font-size: 0.83rem; max-height: calc(100vh - 100px); overflow-y: auto; }
.doc-sidebar nav { border-left: 2px solid var(--border); padding-left: 16px; }
.doc-sidebar a { display: block; color: var(--ink-soft); padding: 4px 0; line-height: 1.5; }
.doc-sidebar a:hover { color: var(--teal-dark); text-decoration: none; }
.toc-h2 { font-weight: 600; color: var(--ink); margin-top: 12px; }
.toc-h2:first-child { margin-top: 0; }
.toc-h3 { padding-left: 12px; font-size: 0.93em; }

.doc-meta {
  display: flex; gap: 18px; flex-wrap: wrap;
  font-size: 0.82rem; color: var(--ink-soft);
  margin: 4px 0 32px; padding-bottom: 20px;
  border-bottom: 1px solid var(--border);
}
.doc-meta span { display: inline-flex; align-items: center; gap: 6px; }

@media (max-width: 900px) {
  .doc-layout { grid-template-columns: 1fr; padding-top: 32px; }
  .doc-sidebar { display: none; }
}

/* ===================================================================
   Footer
   =================================================================== */
.site-footer {
  border-top: 1px solid var(--border);
  padding: 40px 0;
  margin-top: 40px;
}
.site-footer .inner {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0 24px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  flex-wrap: wrap;
  gap: 16px;
}
.footer-links { display: flex; gap: 22px; flex-wrap: wrap; }
.footer-links a { color: var(--ink-soft); font-size: 0.88rem; }
.footer-copy { color: var(--ink-faint); font-size: 0.82rem; }

/* ===================================================================
   Misc utilities
   =================================================================== */
.mt-0 { margin-top: 0; }
.text-center { text-align: center; }
.badge {
  display: inline-flex; align-items: center;
  font-size: 0.7rem; font-weight: 700;
  padding: 2px 9px; border-radius: 999px;
  letter-spacing: 0.02em;
}
.badge-blue { background: var(--teal-tint); color: var(--teal-dark); }
.badge-green { background: var(--teal-tint); color: var(--teal-dark); }
.badge-amber { background: var(--amber-tint); color: var(--amber); }