:root {
  color-scheme: dark;
  --bg: #061014;
  --panel: #0c171d;
  --panel-strong: #10232b;
  --ink: #ecf8f7;
  --muted: #a8bec2;
  --accent: #57d3df;
  --accent-strong: #8ff4dc;
  --border: rgba(120, 190, 205, 0.28);
  --shadow: 0 18px 46px rgba(0, 0, 0, 0.32);
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: Inter, "Segoe UI", Arial, sans-serif;
  line-height: 1.62;
  color: var(--ink);
  background:
    radial-gradient(circle at 15% 0%, rgba(87, 211, 223, 0.12), transparent 30rem),
    linear-gradient(180deg, #071115 0%, #05090c 100%);
}

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

code {
  padding: 0.1rem 0.34rem;
  border-radius: 0.35rem;
  background: rgba(255, 255, 255, 0.08);
  color: #d5fffa;
}

.manual-shell {
  display: grid;
  grid-template-columns: minmax(15rem, 18rem) minmax(0, 1fr);
  gap: clamp(1rem, 3vw, 2rem);
  max-width: 1180px;
  margin: 0 auto;
  padding: clamp(1rem, 3vw, 2rem);
}

.manual-sidebar {
  position: sticky;
  top: 1rem;
  align-self: start;
  padding: 1rem;
  border: 1px solid var(--border);
  border-radius: 1rem;
  background: rgba(8, 18, 24, 0.9);
  box-shadow: var(--shadow);
}

.manual-back-link {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  margin-bottom: 0.9rem;
  padding: 0.35rem 0.7rem;
  border-radius: 0.5rem;
  border: 1px solid var(--border);
  background: rgba(87, 211, 223, 0.08);
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--accent-strong);
  text-decoration: none;
  transition: background 0.15s, border-color 0.15s;
}

.manual-back-link:hover {
  background: rgba(87, 211, 223, 0.16);
  border-color: rgba(87, 211, 223, 0.55);
}

.manual-brand {
  margin: 0 0 0.35rem;
  font-size: 0.78rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent);
}

.manual-sidebar h1 {
  margin: 0 0 0.75rem;
  font-size: 1.25rem;
  line-height: 1.15;
}

.manual-nav {
  display: grid;
  gap: 0.35rem;
  margin-top: 1rem;
}

.manual-nav a {
  display: block;
  padding: 0.5rem 0.6rem;
  border-radius: 0.65rem;
  color: var(--ink);
  text-decoration: none;
}

.manual-nav a:hover,
.manual-nav a[aria-current="page"] {
  background: rgba(87, 211, 223, 0.12);
  color: #ffffff;
}

.manual-content {
  min-width: 0;
}

.chapter-card {
  padding: clamp(1.1rem, 3vw, 2rem);
  border: 1px solid var(--border);
  border-radius: 1.2rem;
  background: rgba(10, 21, 27, 0.94);
  box-shadow: var(--shadow);
}

.chapter-kicker {
  margin: 0 0 0.35rem;
  color: var(--accent);
  font-size: 0.8rem;
  font-weight: 800;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

h1,
h2,
h3 {
  line-height: 1.18;
}

h1 {
  margin: 0 0 0.55rem;
  font-size: clamp(2rem, 5vw, 3.35rem);
}

h2 {
  margin: 1.65rem 0 0.45rem;
  font-size: 1.28rem;
}

h3 {
  margin: 1.2rem 0 0.35rem;
  font-size: 1.04rem;
}

.muted {
  color: var(--muted);
}

.lead {
  margin: 0 0 1.2rem;
  max-width: 68ch;
  color: #c9dcdf;
  font-size: 1.05rem;
}

.manual-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr));
  gap: 0.85rem;
}

.manual-tile,
.callout {
  padding: 0.85rem 1rem;
  border: 1px solid var(--border);
  border-radius: 0.9rem;
  background: var(--panel);
}

.manual-tile h2,
.manual-tile h3 {
  margin-top: 0;
}

.manual-tile a {
  font-weight: 700;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

.figure-card {
  margin: 1.2rem 0;
  padding: 0.65rem;
  border: 1px solid rgba(148, 209, 219, 0.35);
  border-radius: 1rem;
  background: #071116;
  box-shadow: 0 14px 36px rgba(0, 0, 0, 0.34);
}

.figure-card img {
  display: block;
  width: 100%;
  height: auto;
  border-radius: 0.72rem;
  border: 1px solid rgba(255, 255, 255, 0.08);
  background: #0b1116;
}

.figure-card figcaption {
  margin: 0.65rem 0.25rem 0.15rem;
  color: var(--muted);
  font-size: 0.92rem;
}

.next-prev {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 0.7rem;
  margin-top: 1.4rem;
}

.next-prev a {
  padding: 0.55rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 999px;
  text-decoration: none;
  background: rgba(87, 211, 223, 0.1);
}

@media (max-width: 820px) {
  .manual-shell {
    grid-template-columns: 1fr;
  }

  .manual-sidebar {
    position: static;
  }
}