:root {
  --serif: 'Source Serif 4', Georgia, serif;
  --sans: 'Manrope', -apple-system, BlinkMacSystemFont, sans-serif;
  --mono: 'IBM Plex Mono', monospace;
  --bg: #fdfcf9; --paper: #ffffff; --text: #2f2a22; --muted: #6e665b;
  --border: #e2d8c6; --accent: #2c6fb7; --accent-hover: #1e528a;

  --cell-empty: #ffffff;
  --cell-wall: #2f2a22;
  --cell-mud: #b08a52;
  --cell-start: #1e7770;
  --cell-goal: #d9622b;
  --cell-frontier: #f2cf6a;
  --cell-explored: #c8d8ee;
  --cell-path: #d9622b;
}
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; font-family: var(--serif); color: var(--text); background: var(--bg); line-height: 1.65; }
.article { max-width: 1040px; margin: 0 auto; padding: 2.5rem 1.5rem 5rem; }
.back-link { display: inline-block; margin-bottom: 1.5rem; color: var(--muted); text-decoration: none; font-family: var(--sans); font-size: 0.9rem; }
.back-link:hover { color: var(--text); }
.article-header { margin-bottom: 3rem; text-align: center; }
.kicker { margin: 0 0 0.75rem; font-family: var(--sans); font-size: 0.8rem; text-transform: uppercase; letter-spacing: 0.14em; color: var(--muted); }
h1 { margin: 0 auto 1rem; font-size: clamp(2.4rem, 5vw, 3.5rem); line-height: 1.1; letter-spacing: -0.02em; color: #1a1815; max-width: 18ch; }
.abstract { margin: 0 auto 1rem; max-width: 64ch; font-size: 1.15rem; color: #4d463d; }
.byline { display: flex; gap: 1rem; justify-content: center; flex-wrap: wrap; margin-top: 1.4rem; padding-top: 1rem; border-top: 1px solid var(--border); color: var(--muted); font-family: var(--sans); font-size: 0.92rem; }

.step-section {
  position: relative; margin-top: 4rem; padding: 3rem 2.5rem;
  background: var(--paper); border: 1px solid var(--border);
  border-radius: 24px; box-shadow: 0 8px 30px rgba(0, 0, 0, 0.03);
}
.step-badge {
  position: absolute; top: -16px; left: 32px;
  background: var(--accent); color: white;
  font-family: var(--sans); font-weight: 700; font-size: 0.85rem;
  text-transform: uppercase; letter-spacing: 0.08em;
  padding: 0.4rem 1.2rem; border-radius: 999px;
  box-shadow: 0 4px 12px rgba(44, 111, 183, 0.25);
}
h2 { margin: 0 0 1rem; font-size: clamp(1.6rem, 3.5vw, 2.2rem); line-height: 1.15; color: #1a1815; }
p, ul { max-width: 68ch; font-size: 1.08rem; }
li { margin-bottom: 0.5rem; }
.explanation-list { padding-left: 1.5rem; margin: 1rem 0; }
.math-block { margin: 1.2rem 0; padding: 0.6rem 0.8rem; overflow-x: auto; background: rgba(0,0,0,0.02); border-radius: 12px; text-align: center; }

.callout {
  margin: 1.6rem 0; padding: 1.1rem 1.3rem;
  border-left: 4px solid var(--accent);
  background: rgba(44, 111, 183, 0.04);
  border-radius: 0 12px 12px 0; font-size: 1rem;
}
.callout strong { font-family: var(--sans); font-size: 0.9rem; }
.callout--warn { border-left-color: #b86b2a; background: rgba(184,107,42,0.05); }
.callout--key   { border-left-color: #1e7770; background: rgba(30,119,112,0.05); }
.callout--think { border-left-color: #d9622b; background: rgba(217,98,43,0.04); }

@media (max-width: 640px) {
  .article { padding-inline: 1rem; }
  .step-section { padding: 2rem 1.5rem; }
}

/* ===== Controls ===== */
.gs-controls {
  display: flex; align-items: center; gap: 0.7rem; flex-wrap: wrap;
  margin: 0.8rem 0 0.6rem;
  font-family: var(--sans);
}
.gs-controls label { display: flex; align-items: center; gap: 0.45rem; font-size: 0.92rem; }
.gs-controls select {
  font: 600 0.88rem var(--sans);
  padding: 0.4rem 0.55rem; border: 1px solid var(--border);
  border-radius: 8px; background: white;
}
.btn {
  border: 1px solid var(--accent); background: var(--accent); color: white;
  padding: 0.4rem 0.85rem; border-radius: 999px;
  font: 600 0.85rem var(--sans); cursor: pointer;
}
.btn:hover { background: var(--accent-hover); }
.btn--ghost { background: white; color: var(--text); border-color: var(--border); }
.btn--ghost:hover { border-color: var(--accent); color: var(--accent); }
.btn--warn { background: #b86b2a; border-color: #b86b2a; }
.btn--warn:hover { background: #8d4f1d; }
.btn[disabled] { opacity: 0.55; cursor: not-allowed; }

.gs-tools {
  display: flex; gap: 0.4rem; flex-wrap: wrap;
}
.tool-btn {
  border: 1px solid var(--border); background: white; color: var(--text);
  padding: 0.32rem 0.7rem; border-radius: 999px;
  font: 600 0.82rem var(--sans); cursor: pointer;
}
.tool-btn.is-active {
  background: var(--accent); color: white; border-color: var(--accent);
}

.gs-stage {
  background: #fafaf5;
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 0.5rem; margin: 0.6rem 0;
  overflow-x: auto;
}
.gs-canvas {
  display: block;
  cursor: pointer;
  width: 100%;
  height: auto;
  background: white;
  border-radius: 6px;
  image-rendering: pixelated;
  user-select: none;
}

.gs-status {
  font-family: var(--mono); font-size: 0.85rem; color: var(--muted);
  background: rgba(0,0,0,0.03); padding: 0.4rem 0.7rem; border-radius: 8px;
  margin: 0.3rem 0 0.6rem; min-height: 1.7em;
}
.gs-status strong { color: var(--text); font-weight: 600; }

.gs-legend {
  display: flex; flex-wrap: wrap; gap: 0.9rem;
  font-family: var(--sans); font-size: 0.82rem; color: var(--muted);
  margin: 0.2rem 0 0.6rem;
}
.gs-legend-sw {
  display: inline-block; width: 0.85rem; height: 0.85rem;
  border: 1px solid var(--border); border-radius: 3px;
  margin-right: 0.35rem; vertical-align: middle;
}

/* Four-up comparison grid */
.gs-quad {
  display: grid; grid-template-columns: 1fr 1fr; gap: 0.6rem;
  margin: 0.7rem 0;
}
@media (max-width: 720px) { .gs-quad { grid-template-columns: 1fr; } }
.gs-quad-card {
  background: #fafaf5; border: 1px solid var(--border); border-radius: 12px;
  padding: 0.5rem; display: flex; flex-direction: column; gap: 0.3rem;
}
.gs-quad-card h4 {
  margin: 0; font-family: var(--sans); font-weight: 700; font-size: 0.88rem;
  color: var(--text);
}
.gs-quad-card canvas {
  width: 100%; aspect-ratio: 5/3; background: white;
  border: 1px solid var(--border); border-radius: 6px; image-rendering: pixelated;
}
.gs-quad-card .gs-quad-meta {
  font-family: var(--mono); font-size: 0.78rem; color: var(--muted);
  display: flex; justify-content: space-between;
}
.gs-quad-card .gs-quad-meta strong { color: var(--text); font-weight: 600; }

/* Comparison table */
.gs-table { width: 100%; border-collapse: collapse; margin: 1rem 0; font-family: var(--sans); font-size: 0.92rem; }
.gs-table th, .gs-table td { border: 1px solid var(--border); padding: 0.5rem 0.7rem; text-align: left; vertical-align: top; }
.gs-table th { background: rgba(44, 111, 183, 0.06); font-weight: 600; }
.gs-table code { font-family: var(--mono); font-size: 0.85rem; background: rgba(0,0,0,0.04); padding: 0.1rem 0.35rem; border-radius: 4px; }