:root {
  --bg: #fbfbfa;
  --bg-panel: #ffffff;
  --bg-sunken: #f4f4f2;
  --border: #e3e2de;
  --border-strong: #cfcec8;
  --text: #1c1b19;
  --text-dim: #605d57;
  --text-faint: #8b877f;
  --accent: #b4501e;
  --accent-soft: #fdf0e8;
  --ok: #2f6b45;
  --ok-soft: #eaf4ee;
  --warn: #8a6100;
  --warn-soft: #fdf4e0;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, Roboto, sans-serif;
  --radius: 8px;
  --shadow: 0 1px 2px rgba(28, 27, 25, .05), 0 4px 12px rgba(28, 27, 25, .04);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #16161a;
    --bg-panel: #1e1e23;
    --bg-sunken: #131316;
    --border: #2e2e35;
    --border-strong: #414149;
    --text: #eceae6;
    --text-dim: #a8a49c;
    --text-faint: #7c7871;
    --accent: #e8925c;
    --accent-soft: #2b1f16;
    --ok: #7fc59b;
    --ok-soft: #16241c;
    --warn: #e0b355;
    --warn-soft: #262010;
    --shadow: 0 1px 2px rgba(0, 0, 0, .3), 0 4px 14px rgba(0, 0, 0, .25);
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  overflow-x: hidden;
  background: var(--bg);
  color: var(--text);
  font: 15px/1.65 var(--sans);
  -webkit-font-smoothing: antialiased;
}

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
code, pre, kbd { font-family: var(--mono); }

.wrap { max-width: 1080px; margin: 0 auto; padding: 0 24px; }

/* ---------------------------------------------------------------- header */

header.site {
  border-bottom: 1px solid var(--border);
  background: var(--bg-panel);
  padding: 56px 0 44px;
}
.eyebrow {
  font: 600 11px/1 var(--mono);
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 14px;
}
h1 {
  margin: 0 0 14px;
  font-size: clamp(30px, 5vw, 44px);
  line-height: 1.1;
  letter-spacing: -.02em;
  font-weight: 650;
}
.tagline { margin: 0; max-width: 62ch; font-size: 17px; color: var(--text-dim); }
.links { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 26px; }
.btn {
  display: inline-flex; align-items: center; gap: 7px;
  padding: 8px 15px; border-radius: var(--radius);
  border: 1px solid var(--border-strong);
  background: var(--bg-panel); color: var(--text);
  font-size: 14px; font-weight: 500; cursor: pointer;
}
.btn:hover { border-color: var(--text-faint); text-decoration: none; }
.btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn.primary:hover { filter: brightness(1.07); }

nav.toc {
  position: sticky; top: 0; z-index: 20;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
}
nav.toc ul { display: flex; gap: 4px; overflow-x: auto; list-style: none; margin: 0; padding: 0; }
nav.toc a {
  display: block; padding: 12px 12px; font-size: 13.5px;
  color: var(--text-dim); white-space: nowrap; border-bottom: 2px solid transparent;
}
nav.toc a:hover { color: var(--text); text-decoration: none; border-bottom-color: var(--border-strong); }

/* -------------------------------------------------------------- sections */

section { padding: 52px 0; border-bottom: 1px solid var(--border); }
section:last-of-type { border-bottom: 0; }
h2 {
  margin: 0 0 8px; font-size: 24px; font-weight: 620; letter-spacing: -.01em;
  scroll-margin-top: 60px;
}
h3 { margin: 26px 0 8px; font-size: 16px; font-weight: 620; }
.lede { margin: 0 0 24px; color: var(--text-dim); max-width: 68ch; }
p { max-width: 72ch; }

pre {
  margin: 0 0 16px; padding: 14px 16px; overflow-x: auto;
  background: var(--bg-sunken); border: 1px solid var(--border);
  border-radius: var(--radius); font-size: 13px; line-height: 1.6;
}
p code, li code, td code {
  background: var(--bg-sunken); border: 1px solid var(--border);
  border-radius: 4px; padding: .5px 5px; font-size: .89em;
  overflow-wrap: anywhere;
}

.grid { display: grid; gap: 16px; grid-template-columns: repeat(auto-fit, minmax(240px, 1fr)); }
.card {
  padding: 18px; background: var(--bg-panel);
  border: 1px solid var(--border); border-radius: var(--radius);
}
.card h3 { margin: 0 0 6px; }
.card p { margin: 0; font-size: 14px; color: var(--text-dim); }

table { width: 100%; border-collapse: collapse; font-size: 14px; }
th, td { text-align: left; padding: 9px 12px; border-bottom: 1px solid var(--border); vertical-align: top; }
th { font-size: 12px; text-transform: uppercase; letter-spacing: .06em; color: var(--text-faint); font-weight: 600; }
.scroll-x { overflow-x: auto; border: 1px solid var(--border); border-radius: var(--radius); background: var(--bg-panel); }
/* Scroll a wide table sideways rather than breaking identifiers mid-word. */
.scroll-x table { min-width: 520px; }
.scroll-x td code { overflow-wrap: normal; }

/* ------------------------------------------------------------------ demo */

.demo-bar {
  display: flex; flex-wrap: wrap; align-items: center; gap: 10px; margin-bottom: 16px;
}
.demo-bar label { font-size: 13px; color: var(--text-dim); }
select {
  padding: 7px 10px; font: inherit; font-size: 14px;
  border: 1px solid var(--border-strong); border-radius: var(--radius);
  background: var(--bg-panel); color: var(--text);
}
.editors { display: grid; gap: 16px; grid-template-columns: 1fr 1fr; }
@media (max-width: 780px) { .editors { grid-template-columns: 1fr; } }
.editor { display: flex; flex-direction: column; }
.editor label { font: 600 12px/1 var(--mono); text-transform: uppercase; letter-spacing: .08em; color: var(--text-faint); margin-bottom: 7px; }
textarea {
  width: 100%; min-height: 260px; resize: vertical;
  padding: 12px 14px; font-family: var(--mono); font-size: 12.5px; line-height: 1.6;
  color: var(--text); background: var(--bg-panel);
  border: 1px solid var(--border); border-radius: var(--radius);
  tab-size: 2;
}
textarea:focus { outline: 2px solid var(--accent); outline-offset: -1px; }

.stats { display: flex; flex-wrap: wrap; gap: 10px; margin: 20px 0 0; }
.stat {
  flex: 1 1 130px; padding: 12px 14px; background: var(--bg-panel);
  border: 1px solid var(--border); border-radius: var(--radius);
}
.stat .v { font: 620 22px/1.1 var(--sans); font-variant-numeric: tabular-nums; }
.stat .k { font-size: 11.5px; text-transform: uppercase; letter-spacing: .07em; color: var(--text-faint); margin-top: 4px; }

.notice { padding: 11px 14px; border-radius: var(--radius); font-size: 13.5px; margin: 16px 0 0; }
.notice.err { background: var(--accent-soft); border: 1px solid var(--accent); color: var(--text); }
.notice.warn { background: var(--warn-soft); border: 1px solid var(--warn); color: var(--text); }
.notice.ok { background: var(--ok-soft); border: 1px solid var(--ok); color: var(--text); }
.notice[hidden] { display: none !important; }

.graph-wrap { margin-top: 20px; border: 1px solid var(--border); border-radius: var(--radius); background: var(--bg-panel); }
.graph-head {
  display: flex; flex-wrap: wrap; align-items: center; gap: 14px;
  padding: 10px 14px; border-bottom: 1px solid var(--border); font-size: 13px; color: var(--text-dim);
}
.legend { display: inline-flex; align-items: center; gap: 6px; }
.swatch { width: 11px; height: 11px; border-radius: 3px; border: 1px solid var(--border-strong); }
.graph-scroll { overflow: auto; max-height: 560px; }
svg.graph { display: block; min-width: 100%; }
svg.graph .node rect { fill: var(--bg-sunken); stroke: var(--border-strong); stroke-width: 1.2; cursor: pointer; }
svg.graph .node.initial rect { fill: var(--accent-soft); stroke: var(--accent); stroke-width: 1.8; }
svg.graph .node.goal rect { fill: var(--ok-soft); stroke: var(--ok); stroke-width: 1.8; }
svg.graph .node.selected rect { stroke-width: 2.6; }
svg.graph .node text { font: 11px var(--mono); fill: var(--text); pointer-events: none; }
svg.graph .node .sub { font-size: 9.5px; fill: var(--text-faint); }
svg.graph .edge { fill: none; stroke: var(--border-strong); stroke-width: 1.2; }
svg.graph .edge.hot { stroke: var(--accent); stroke-width: 2; }
svg.graph .elabel { font: 9.5px var(--mono); fill: var(--text-faint); }

.detail { margin-top: 16px; }
.detail h3 { margin-top: 0; }
.atoms { display: flex; flex-wrap: wrap; gap: 6px; list-style: none; padding: 0; margin: 0 0 14px; }
.atoms li {
  font: 11.5px/1.5 var(--mono); padding: 3px 8px; border-radius: 4px;
  background: var(--bg-sunken); border: 1px solid var(--border);
  /* Ground atoms can be very long identifiers (MulVAL predicates in
     particular). Let them break rather than push the page sideways. */
  max-width: 100%; overflow-wrap: anywhere;
}
.atoms li.added { background: var(--ok-soft); border-color: var(--ok); }

/* ----------------------------------------------------------------- fixes */

.fix { padding: 18px 0; border-bottom: 1px solid var(--border); }
.fix:last-child { border-bottom: 0; }
.fix h3 { margin: 0 0 6px; display: flex; flex-wrap: wrap; gap: 9px; align-items: baseline; }
.tag {
  font: 600 10.5px/1 var(--mono); letter-spacing: .06em; text-transform: uppercase;
  padding: 4px 7px; border-radius: 4px; background: var(--accent-soft); color: var(--accent);
  border: 1px solid var(--accent);
}
.fix p { margin: 0 0 10px; font-size: 14.5px; color: var(--text-dim); }
.beforeafter { display: grid; gap: 12px; grid-template-columns: 1fr 1fr; }
@media (max-width: 780px) { .beforeafter { grid-template-columns: 1fr; } }
.beforeafter pre { margin: 0; font-size: 12px; }
.beforeafter .h { font: 600 11px/1 var(--mono); text-transform: uppercase; letter-spacing: .08em; color: var(--text-faint); margin-bottom: 6px; }

footer.site { padding: 36px 0 60px; color: var(--text-faint); font-size: 13.5px; }
footer.site p { margin: 0 0 6px; }
.sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); }