/* 边注 · 学习站 — ink on paper, teal accent */
:root {
  --ink: #1c1917;
  --ink-soft: #44403c;
  --muted: #78716c;
  --paper: #f3efe6;
  --paper-2: #e8e2d6;
  --line: #d6cfc2;
  --accent: #0d5c4d;
  --accent-2: #c45c26;
  --card: rgba(255, 252, 245, 0.72);
  --max: 46rem;
  --side: 14rem;
  --font-display: "Source Serif 4", "Noto Serif SC", Georgia, serif;
  --font-body: "Noto Sans SC", "Source Sans 3", system-ui, sans-serif;
  --font-mono: "IBM Plex Mono", "Noto Sans Mono", ui-monospace, monospace;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--ink);
  font-family: var(--font-body);
  font-size: 1.05rem;
  line-height: 1.75;
  background:
    radial-gradient(ellipse 80% 50% at 10% -10%, rgba(13, 92, 77, 0.08), transparent 50%),
    radial-gradient(ellipse 60% 40% at 100% 0%, rgba(196, 92, 38, 0.06), transparent 45%),
    linear-gradient(180deg, var(--paper) 0%, var(--paper-2) 100%);
  min-height: 100vh;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  opacity: 0.35;
  background-image:
    linear-gradient(var(--line) 1px, transparent 1px),
    linear-gradient(90deg, var(--line) 1px, transparent 1px);
  background-size: 48px 48px;
  mask-image: linear-gradient(180deg, rgba(0, 0, 0, 0.35), transparent 70%);
  z-index: 0;
}

a {
  color: var(--accent);
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

a:hover {
  color: var(--accent-2);
}

.wrap {
  position: relative;
  z-index: 1;
  display: grid;
  grid-template-columns: var(--side) minmax(0, 1fr);
  gap: 2rem;
  max-width: 72rem;
  margin: 0 auto;
  padding: 1.5rem 1.25rem 4rem;
}

@media (max-width: 860px) {
  .wrap {
    grid-template-columns: 1fr;
    padding-top: 1rem;
  }
  .nav {
    position: static !important;
  }
}

.nav {
  position: sticky;
  top: 1rem;
  align-self: start;
  padding: 1rem 0;
}

.brand {
  font-family: var(--font-display);
  font-size: 1.65rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  color: var(--ink);
  text-decoration: none;
  display: block;
  margin-bottom: 0.25rem;
}

.brand-sub {
  font-size: 0.8rem;
  color: var(--muted);
  margin-bottom: 1.25rem;
}

.nav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
}

.nav a {
  color: var(--ink-soft);
  text-decoration: none;
  font-size: 0.92rem;
  padding: 0.35rem 0.5rem;
  border-radius: 4px;
}

.nav a:hover,
.nav a[aria-current="page"] {
  background: var(--card);
  color: var(--accent);
}

.main {
  max-width: var(--max);
  padding-top: 0.5rem;
}

.hero {
  margin-bottom: 2rem;
}

.hero h1 {
  font-family: var(--font-display);
  font-size: clamp(1.85rem, 4vw, 2.45rem);
  font-weight: 600;
  line-height: 1.25;
  margin: 0 0 0.75rem;
  letter-spacing: -0.01em;
}

.hero p.lede {
  margin: 0;
  color: var(--ink-soft);
  font-size: 1.08rem;
  max-width: 36rem;
}

.meta {
  margin-top: 0.85rem;
  font-size: 0.82rem;
  color: var(--muted);
}

h2 {
  font-family: var(--font-display);
  font-size: 1.45rem;
  margin: 2.4rem 0 0.85rem;
  padding-top: 0.5rem;
  border-top: 1px solid var(--line);
}

h3 {
  font-size: 1.08rem;
  margin: 1.5rem 0 0.5rem;
  color: var(--ink);
}

p {
  margin: 0.65rem 0;
}

ul,
ol {
  margin: 0.5rem 0 0.85rem;
  padding-left: 1.25rem;
}

li {
  margin: 0.3rem 0;
}

.figure {
  margin: 1.25rem 0 1.5rem;
  padding: 1rem;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 2px;
  overflow-x: auto;
}

.figure svg {
  display: block;
  width: 100%;
  height: auto;
  max-width: 640px;
  margin: 0 auto;
}

.figcap {
  margin: 0.75rem 0 0;
  font-size: 0.85rem;
  color: var(--muted);
  text-align: center;
}

.note {
  margin: 1rem 0;
  padding: 0.85rem 1rem;
  border-left: 3px solid var(--accent);
  background: rgba(13, 92, 77, 0.06);
  font-size: 0.95rem;
}

.warn {
  border-left-color: var(--accent-2);
  background: rgba(196, 92, 38, 0.08);
}

pre,
.code {
  font-family: var(--font-mono);
  font-size: 0.86rem;
  line-height: 1.55;
  background: #1c1917;
  color: #f5f0e8;
  padding: 1rem 1.1rem;
  overflow-x: auto;
  border-radius: 2px;
  margin: 0.85rem 0;
}

code {
  font-family: var(--font-mono);
  font-size: 0.88em;
  background: rgba(28, 25, 23, 0.08);
  padding: 0.1em 0.35em;
  border-radius: 3px;
}

pre code {
  background: none;
  padding: 0;
  color: inherit;
}

table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92rem;
  margin: 0.85rem 0 1.2rem;
}

th,
td {
  border: 1px solid var(--line);
  padding: 0.45rem 0.6rem;
  text-align: left;
  vertical-align: top;
}

th {
  background: rgba(28, 25, 23, 0.05);
  font-weight: 600;
}

.cards {
  display: grid;
  gap: 0.85rem;
  margin: 1.25rem 0 2rem;
}

.card {
  display: block;
  padding: 1rem 1.1rem;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 2px;
  text-decoration: none;
  color: inherit;
  transition: border-color 0.15s, transform 0.15s;
}

.card:hover {
  border-color: var(--accent);
  transform: translateY(-1px);
  color: inherit;
}

.card strong {
  font-family: var(--font-display);
  font-size: 1.15rem;
  display: block;
  margin-bottom: 0.25rem;
  color: var(--accent);
}

.card span {
  color: var(--ink-soft);
  font-size: 0.92rem;
}

.footer {
  margin-top: 3rem;
  padding-top: 1rem;
  border-top: 1px solid var(--line);
  font-size: 0.82rem;
  color: var(--muted);
}

.kicker {
  font-size: 0.75rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 0.35rem;
}