:root {
  --bg: #0b0c10;
  --card: #11131a;
  --text: #e9eef7;
  --muted: #b8c0d4;
  --link: #7aa6ff;
  --border: rgba(255,255,255,.10);
  --shadow: 0 10px 30px rgba(0,0,0,.35);
  --mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
  --sans: ui-sans-serif, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji", "Segoe UI Emoji";
}

@media (prefers-color-scheme: light) {
  :root {
    --bg: #f7f8fb;
    --card: #ffffff;
    --text: #101828;
    --muted: #475467;
    --link: #1d4ed8;
    --border: rgba(16,24,40,.12);
    --shadow: 0 10px 30px rgba(16,24,40,.10);
  }
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  padding: 0;
  font-family: var(--sans);
  background: var(--bg);
  color: var(--text);
}

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

.wrap {
  max-width: 980px;
  margin: 0 auto;
  padding: 28px 18px 60px;
}

header {
  margin-bottom: 18px;
}

.hero {
  display: grid;
  grid-template-columns: 1fr;
  gap: 18px;
  align-items: center;
}

h1 {
  margin: 0;
  font-size: 34px;
  line-height: 1.1;
  letter-spacing: -0.02em;
}

.tagline {
  margin-top: 8px;
  color: var(--muted);
}

.meta {
  display: flex;
  flex-wrap: wrap;
  gap: 10px 14px;
  margin-top: 10px;
  color: var(--muted);
  font-size: 14px;
}

.meta span {
  display: inline-flex;
  gap: 8px;
  align-items: center;
}

nav {
  position: sticky;
  top: 0;
  z-index: 10;
  backdrop-filter: blur(8px);
  background: color-mix(in srgb, var(--bg) 84%, transparent);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 10px 12px;
  margin: 18px 0 22px;
  box-shadow: var(--shadow);
}

nav a {
  display: inline-block;
  padding: 8px 10px;
  border-radius: 10px;
  font-size: 14px;
  color: var(--muted);
  border: 1px solid transparent;
}

nav a:hover {
  color: var(--text);
  border-color: var(--border);
  text-decoration: none;
}

.grid {
  display: grid;
  grid-template-columns: 1.25fr 0.75fr;
  gap: 18px;
  align-items: start;
}

@media (max-width: 860px) {
  .grid { grid-template-columns: 1fr; }
  nav { position: relative; top: auto; }
}

section,
aside {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 16px;
  padding: 16px 16px 10px;
  box-shadow: var(--shadow);
}

section { margin-bottom: 18px; }

h2 {
  margin: 0 0 10px;
  font-size: 18px;
  letter-spacing: -0.01em;
}

p {
  margin: 0 0 10px;
  color: var(--text);
  line-height: 1.6;
}

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

ul {
  margin: 0;
  padding-left: 18px;
}

li {
  margin: 8px 0;
  line-height: 1.5;
}

.item {
  padding: 12px;
  border-radius: 12px;
  border: 1px solid var(--border);
  margin-bottom: 10px;
}

.item:last-child { margin-bottom: 6px; }
.item-title { font-weight: 650; }
.item-meta { color: var(--muted); font-size: 14px; margin-top: 4px; }

.pill {
  display: inline-block;
  font-family: var(--mono);
  font-size: 12px;
  color: var(--muted);
  border: 1px solid var(--border);
  padding: 2px 8px;
  border-radius: 999px;
  margin-right: 6px;
  margin-top: 6px;
}

.note-list {
  display: grid;
  gap: 12px;
}

.callout {
  border-left: 3px solid var(--link);
  padding-left: 12px;
}

footer {
  margin-top: 22px;
  color: var(--muted);
  font-size: 13px;
  text-align: center;
}

.math {
  overflow-x: auto;
}