:root {
  --ink: #16202b;
  --ink-soft: #55636f;
  --line: #dde3e9;
  --bg: #ffffff;
  --bg-soft: #f5f7f9;
  --accent: #0b6b5f;
  --accent-soft: #e3f1ee;
  --code-bg: #1d2733;
  --max: 1240px;
}

* { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.65 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ---------- masthead ---------- */

.masthead {
  background: var(--ink);
  color: #fff;
  border-bottom: 3px solid var(--accent);
}

.masthead-inner {
  max-width: var(--max);
  margin: 0 auto;
  padding: 14px 24px;
  display: flex;
  align-items: center;
  gap: 20px;
}

.brand { display: flex; align-items: center; gap: 12px; color: #fff; }
.brand:hover { text-decoration: none; }

.brand-mark {
  display: inline-block;
  padding: 6px 10px;
  border: 1px solid rgba(255, 255, 255, 0.35);
  border-radius: 6px;
  font: 700 13px/1 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  letter-spacing: 0.12em;
}

.brand-text strong { display: block; font-size: 17px; letter-spacing: 0.01em; }
.brand-text small { display: block; color: #a9b6c2; font-size: 12.5px; }

.masthead-links { margin-left: auto; display: flex; gap: 22px; }
.masthead-links a { color: #cfd8e0; font-size: 14px; }
.masthead-links a:hover { color: #fff; }

.nav-toggle {
  display: none;
  margin-left: auto;
  background: transparent;
  color: #cfd8e0;
  border: 1px solid rgba(255, 255, 255, 0.3);
  border-radius: 6px;
  padding: 6px 12px;
  font-size: 14px;
  cursor: pointer;
}

/* ---------- layout ---------- */

.page {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0 24px;
  display: grid;
  grid-template-columns: 260px minmax(0, 1fr);
  gap: 48px;
  align-items: start;
}

.sidebar {
  position: sticky;
  top: 0;
  max-height: 100vh;
  overflow-y: auto;
  padding: 32px 0 48px;
  border-right: 1px solid var(--line);
}

.nav-group { margin-bottom: 26px; padding-right: 18px; }

.nav-group h2 {
  margin: 0 0 8px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-soft);
}

.nav-group ul { list-style: none; margin: 0; padding: 0; }

.nav-group li a {
  display: block;
  padding: 4px 10px;
  margin-left: -10px;
  border-radius: 5px;
  color: var(--ink);
  font-size: 14px;
}

.nav-group li a:hover { background: var(--bg-soft); text-decoration: none; }

.nav-group li.current a {
  background: var(--accent-soft);
  color: var(--accent);
  font-weight: 600;
}

.content {
  padding: 36px 0 64px;
  min-width: 0;
}

/* ---------- typography ---------- */

.content h1, .content h2, .content h3, .content h4 {
  line-height: 1.3;
  margin: 1.8em 0 0.6em;
}

.page-title, .content h1 {
  margin-top: 0;
  font-size: 32px;
  letter-spacing: -0.01em;
}

.content h2 {
  font-size: 23px;
  padding-bottom: 6px;
  border-bottom: 1px solid var(--line);
}

.content h3 { font-size: 18px; }

.content p, .content li { overflow-wrap: break-word; }

.content img { max-width: 100%; }

.content table {
  border-collapse: collapse;
  width: 100%;
  margin: 1.2em 0;
  font-size: 14.5px;
  display: block;
  overflow-x: auto;
}

.content th, .content td {
  border: 1px solid var(--line);
  padding: 7px 11px;
  text-align: left;
}

.content th { background: var(--bg-soft); }

.content blockquote {
  margin: 1.2em 0;
  padding: 2px 18px;
  border-left: 3px solid var(--accent);
  background: var(--bg-soft);
  color: var(--ink-soft);
}

code, pre, tt {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", monospace;
}

.content :not(pre) > code {
  background: var(--bg-soft);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: 1px 5px;
  font-size: 87%;
}

.content pre {
  background: var(--code-bg);
  color: #e6edf3;
  padding: 15px 18px;
  border-radius: 8px;
  overflow-x: auto;
  font-size: 13.5px;
  line-height: 1.55;
}

.content pre code { background: none; border: 0; padding: 0; color: inherit; font-size: inherit; }

.content .mermaid {
  margin: 1.6em 0;
  padding: 12px;
  overflow-x: auto;
  background: var(--bg-soft);
  border: 1px solid var(--line);
  border-radius: 8px;
  text-align: center;
}

.content hr { border: 0; border-top: 1px solid var(--line); margin: 2.2em 0; }

.source-link {
  margin-top: 3.5em;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  font-size: 14px;
}

/* ---------- landing page ---------- */

.hero {
  padding: 8px 0 6px;
  border-bottom: 1px solid var(--line);
  margin-bottom: 34px;
}

.hero h1 { font-size: 38px; margin: 0 0 12px; letter-spacing: -0.02em; }
.hero p { font-size: 17px; color: var(--ink-soft); max-width: 64ch; margin: 0 0 18px; }

.hero-actions { display: flex; flex-wrap: wrap; gap: 10px; margin-bottom: 26px; }

.button {
  display: inline-block;
  padding: 8px 16px;
  border-radius: 6px;
  border: 1px solid var(--accent);
  background: var(--accent);
  color: #fff;
  font-size: 14.5px;
}

.button:hover { text-decoration: none; opacity: 0.9; }
.button.secondary { background: #fff; color: var(--accent); }

.category { margin-bottom: 40px; }

.category > h2 {
  margin: 0 0 4px;
  font-size: 21px;
  border: 0;
  padding: 0;
}

.category > p { margin: 0 0 16px; color: var(--ink-soft); font-size: 15px; }

.cards {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(255px, 1fr));
  gap: 14px;
}

.card {
  display: block;
  padding: 14px 16px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: #fff;
  color: var(--ink);
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

.card:hover {
  text-decoration: none;
  border-color: var(--accent);
  box-shadow: 0 2px 10px rgba(11, 107, 95, 0.09);
}

.card strong { display: block; margin-bottom: 4px; color: var(--accent); font-size: 15px; }
.card span { display: block; font-size: 13.5px; color: var(--ink-soft); line-height: 1.5; }

/* ---------- footer ---------- */

.site-footer {
  border-top: 1px solid var(--line);
  background: var(--bg-soft);
}

.site-footer p {
  max-width: var(--max);
  margin: 0 auto;
  padding: 20px 24px;
  font-size: 13.5px;
  color: var(--ink-soft);
}

/* ---------- responsive ---------- */

@media (max-width: 860px) {
  .masthead-links { display: none; }
  .nav-toggle { display: inline-block; }
  .page { grid-template-columns: minmax(0, 1fr); gap: 0; padding: 0 18px; }
  .sidebar {
    display: none;
    position: static;
    max-height: none;
    border-right: 0;
    border-bottom: 1px solid var(--line);
    padding: 20px 0;
  }
  .sidebar.open { display: block; }
  .hero h1 { font-size: 30px; }
}