:root {
  --bg: #0f1419;
  --fg: #e7ecf1;
  --muted: #9aa7b5;
  --accent: #6cb6ff;
  --accent2: #7fd99a;
  --card: #1a222c;
  --border: #2a3542;
  --code-bg: #121820;
  --kw: #c792ea;
  --op: #89ddff;
  --num: #f78c6c;
  --str: #c3e88d;
  --cmt: #697098;
  --id: #e7ecf1;
}

* { box-sizing: border-box; }
html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--fg);
  font: 16px/1.55 system-ui, -apple-system, "Segoe UI", sans-serif;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

.wrap {
  max-width: 52rem;
  margin: 0 auto;
  padding: 1.25rem 1.25rem 3rem;
}

header.site {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.75rem 1.5rem;
  padding-bottom: 1rem;
  border-bottom: 1px solid var(--border);
  margin-bottom: 1.5rem;
}
header.site .brand {
  font-weight: 700;
  font-size: 1.15rem;
  color: var(--fg);
  letter-spacing: 0.02em;
}
header.site .brand span { color: var(--accent2); font-weight: 600; }
nav.top {
  display: flex;
  flex-wrap: wrap;
  gap: 0.85rem;
  font-size: 0.95rem;
}
nav.top a.soon { color: var(--muted); }
nav.top a[aria-current="page"] { color: var(--accent2); font-weight: 600; }

h1 { font-size: 1.75rem; margin: 0 0 0.5rem; font-weight: 700; }
h2 { font-size: 1.2rem; margin: 1.75rem 0 0.5rem; font-weight: 650; }
p.lead { color: var(--muted); font-size: 1.05rem; margin: 0 0 1.25rem; }
p { margin: 0.6rem 0; }
.muted { color: var(--muted); }
.card {
  background: var(--card);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 1rem 1.1rem;
  margin: 1rem 0;
}
.card h2 { margin-top: 0; }
.cards {
  display: grid;
  gap: 0.85rem;
  grid-template-columns: repeat(auto-fit, minmax(14rem, 1fr));
}
.cards a.card {
  color: inherit;
  display: block;
  transition: border-color 0.15s;
}
.cards a.card:hover {
  border-color: var(--accent);
  text-decoration: none;
}
.cards a.card .label { color: var(--accent); font-weight: 600; }
.cards a.card.disabled {
  opacity: 0.65;
  pointer-events: none;
}
.badge {
  display: inline-block;
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--bg);
  background: var(--muted);
  border-radius: 3px;
  padding: 0.1rem 0.4rem;
  margin-left: 0.35rem;
  vertical-align: middle;
}

pre, .cm-wrap {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0.85rem 1rem;
  overflow-x: auto;
  font: 0.9rem/1.45 ui-monospace, "Cascadia Code", "SF Mono", Menlo, Consolas, monospace;
}
pre { margin: 0.5rem 0 1rem; }
.example { margin: 1.25rem 0; }
.example h3 {
  font-size: 1rem;
  margin: 0 0 0.35rem;
  font-weight: 650;
}
.example .note { color: var(--muted); font-size: 0.9rem; margin-bottom: 0.4rem; }

footer.site {
  margin-top: 2.5rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
  color: var(--muted);
  font-size: 0.85rem;
}

/* CodeMirror 6 host */
.editor {
  border: 1px solid var(--border);
  border-radius: 6px;
  overflow: hidden;
  background: var(--code-bg);
  min-height: 12rem;
}
.editor .cm-editor { height: 100%; font-size: 0.9rem; }
.editor .cm-scroller { font-family: ui-monospace, "Cascadia Code", Menlo, Consolas, monospace; }
.cm-aptop-keyword { color: var(--kw); font-weight: 600; }
.cm-aptop-operator { color: var(--op); }
.cm-aptop-number { color: var(--num); }
.cm-aptop-comment { color: var(--cmt); font-style: italic; }
.cm-aptop-bool { color: var(--str); }

/* Book + course — hard to miss */
.sources {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem;
  margin: 0 0 1.25rem;
}
.sources a {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.55rem 0.95rem;
  border-radius: 6px;
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--fg);
  font-weight: 600;
  font-size: 0.95rem;
  text-decoration: none;
}
.sources a:hover {
  border-color: var(--accent);
  text-decoration: none;
  background: #1e2833;
}
.sources a.book { border-color: var(--accent); color: var(--accent); }
.sources a.course { border-color: var(--accent2); color: var(--accent2); }
.sources .hint {
  flex: 1 1 12rem;
  color: var(--muted);
  font-size: 0.85rem;
  align-self: center;
}

nav.top a.ext {
  color: var(--accent);
  font-weight: 600;
}
nav.top a.ext.course { color: var(--accent2); }

.toolbar-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  align-items: center;
  margin: 0.75rem 0;
}
.toolbar-row button, .toolbar-row select {
  font: inherit;
  padding: 0.4rem 0.75rem;
  border-radius: 5px;
  border: 1px solid var(--border);
  background: var(--card);
  color: var(--fg);
  cursor: pointer;
}
.toolbar-row button.primary {
  background: var(--accent);
  color: var(--bg);
  border-color: var(--accent);
  font-weight: 650;
}
.toolbar-row button:disabled { opacity: 0.5; cursor: wait; }
.toolbar-row .hint { color: var(--muted); font-size: 0.85rem; }
.out {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  padding: 0.75rem 1rem;
  min-height: 4rem;
  white-space: pre-wrap;
  font: 0.85rem/1.45 ui-monospace, Menlo, Consolas, monospace;
  color: var(--fg);
  margin-top: 0.75rem;
}
.out.err { border-color: #e06c75; color: #e06c75; }
.out.ok { border-color: var(--accent2); }
.exp-hint {
  color: var(--muted);
  font-size: 0.8rem;
  margin: 0.35rem 0 0;
}