:root {
  color-scheme: light;
  --bg: #f7f8f5;
  --panel: #ffffff;
  --ink: #1e2528;
  --muted: #5b666b;
  --line: #d8ddd8;
  --accent: #2f6f73;
  --accent-strong: #205458;
  --soft: #eaf3f1;
  --warn: #f6efe3;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: Inter, ui-sans-serif, system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  line-height: 1.6;
}

a {
  color: var(--accent-strong);
}

.layout {
  min-height: 100vh;
  display: grid;
  grid-template-columns: 280px minmax(0, 1fr);
}

.sidebar {
  position: sticky;
  top: 0;
  height: 100vh;
  padding: 28px 20px;
  border-right: 1px solid var(--line);
  background: #fbfcfa;
}

.brand {
  margin-bottom: 28px;
}

.brand a {
  color: var(--ink);
  text-decoration: none;
}

.brand-title {
  display: block;
  font-size: 1.04rem;
  font-weight: 760;
  line-height: 1.2;
}

.brand-subtitle {
  display: block;
  margin-top: 8px;
  color: var(--muted);
  font-size: 0.9rem;
}

.nav {
  display: grid;
  gap: 8px;
}

.nav a {
  min-height: 44px;
  display: flex;
  align-items: center;
  padding: 10px 12px;
  border: 1px solid transparent;
  border-radius: 8px;
  color: var(--ink);
  font-size: 0.94rem;
  font-weight: 650;
  text-decoration: none;
}

.nav a:hover,
.nav a.active {
  background: var(--soft);
  border-color: #c8ded9;
  color: var(--accent-strong);
}

.content {
  max-width: 980px;
  width: 100%;
  padding: 48px 48px 72px;
}

.eyebrow {
  color: var(--accent-strong);
  font-size: 0.82rem;
  font-weight: 760;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

h1 {
  margin: 8px 0 12px;
  font-size: clamp(2rem, 4vw, 3.4rem);
  line-height: 1.05;
  letter-spacing: 0;
}

h2 {
  margin: 44px 0 12px;
  padding-top: 18px;
  border-top: 1px solid var(--line);
  font-size: 1.55rem;
  line-height: 1.2;
}

h3 {
  margin: 28px 0 10px;
  font-size: 1.13rem;
}

p {
  margin: 0 0 16px;
}

ul,
ol {
  margin: 0 0 18px;
  padding-left: 1.35rem;
}

li + li {
  margin-top: 6px;
}

.meta {
  display: grid;
  gap: 4px;
  max-width: 720px;
  margin: 18px 0 30px;
  padding: 16px 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
  color: var(--muted);
}

.meta strong {
  color: var(--ink);
}

.lead {
  max-width: 780px;
  color: #3f4c50;
  font-size: 1.12rem;
}

.callout {
  margin: 24px 0;
  padding: 18px 20px;
  border-left: 4px solid var(--accent);
  background: var(--soft);
}

.grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 16px;
  margin: 18px 0 24px;
}

.tile {
  padding: 18px;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
}

.tile h3 {
  margin-top: 0;
}

.diagram {
  margin: 22px 0;
  padding: 20px;
  overflow-x: auto;
  border: 1px solid var(--line);
  border-radius: 8px;
  background: var(--panel);
}

footer {
  margin-top: 56px;
  padding-top: 22px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 0.9rem;
}

@media (max-width: 860px) {
  .layout {
    display: block;
  }

  .sidebar {
    position: static;
    height: auto;
    padding: 18px;
    border-right: 0;
    border-bottom: 1px solid var(--line);
  }

  .nav {
    grid-template-columns: 1fr;
  }

  .content {
    padding: 32px 20px 56px;
  }

  .grid {
    grid-template-columns: 1fr;
  }
}