:root {
  --ink: #0a0a0a;
  --muted: #6b7280;
  --faint: #9ca3af;
  --line: #ececec;
  --surface: #fafafa;
  --surface2: #f4f4f5;
  --accent: #2563eb;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: #fff;
  color: var(--ink);
  font-family: Inter, ui-sans-serif, system-ui, sans-serif;
  -webkit-font-smoothing: antialiased;
  line-height: 1.5;
}
.wrap { width: 100%; max-width: 980px; margin: 0 auto; padding: 0 20px; }
.muted { color: var(--muted); }
.small { font-size: 13px; }
.accent { color: var(--accent); }
code { font-family: "JetBrains Mono", ui-monospace, monospace; font-size: 0.9em; background: var(--surface2); padding: 1px 6px; border-radius: 6px; }

/* nav */
.nav { position: sticky; top: 0; z-index: 10; background: rgba(255,255,255,0.85); backdrop-filter: blur(8px); border-bottom: 1px solid var(--line); }
.nav-inner { display: flex; align-items: center; justify-content: space-between; height: 60px; }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 700; text-decoration: none; color: var(--ink); font-size: 17px; }
.nav-links { display: flex; gap: 20px; }
.nav-links a { color: var(--muted); text-decoration: none; font-size: 14px; font-weight: 500; }
.nav-links a:hover { color: var(--ink); }

/* hero */
.hero { padding: 56px 0 28px; }
.chip { display: inline-flex; align-items: center; gap: 8px; border: 1px solid var(--line); border-radius: 999px; padding: 5px 12px; font-size: 12px; font-weight: 600; color: var(--muted); }
.chip .dot { width: 7px; height: 7px; border-radius: 50%; background: #16a34a; }
h1 { font-size: 44px; line-height: 1.05; letter-spacing: -0.02em; margin: 20px 0 0; font-weight: 800; }
.lead { font-size: 18px; color: var(--muted); max-width: 720px; margin: 18px 0 0; }

/* layout */
.grid { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; margin: 12px 0 24px; }
.card { border: 1px solid var(--line); border-radius: 18px; background: #fff; box-shadow: 0 1px 2px rgba(10,10,10,0.04), 0 10px 30px rgba(10,10,10,0.05); }
.pad { padding: 22px; }
.card-head { display: flex; align-items: center; justify-content: space-between; padding: 16px 20px; border-bottom: 1px solid var(--line); }
.card-title { font-weight: 700; font-size: 15px; }

textarea { width: 100%; border: 1px solid var(--line); border-radius: 12px; padding: 12px 14px; font: inherit; resize: vertical; background: var(--surface); }
textarea:focus { outline: none; border-color: var(--accent); }
.row { display: flex; align-items: center; gap: 12px; margin-top: 12px; }
.btn { background: var(--ink); color: #fff; border: 0; border-radius: 12px; padding: 11px 18px; font-weight: 600; font-size: 14px; cursor: pointer; transition: opacity .15s; }
.btn:hover { opacity: 0.9; }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }
.status { font-size: 14px; min-height: 18px; margin: 12px 0 0; }
.status a { color: var(--accent); }
.hint { margin: 12px 0 0; }

/* board */
.board { list-style: none; margin: 0; padding: 0; max-height: 360px; overflow-y: auto; }
.board li { padding: 13px 20px; border-bottom: 1px solid var(--line); }
.board li:last-child { border-bottom: 0; }
.msg-top { display: flex; align-items: center; justify-content: space-between; gap: 10px; }
.who { font-family: "JetBrains Mono", monospace; font-size: 12px; color: var(--faint); }
.tag { font-size: 11px; font-weight: 600; border-radius: 999px; padding: 2px 8px; }
.tag.onchain { background: #ecfdf3; color: #16a34a; }
.tag.demo { background: var(--surface2); color: var(--muted); }
.tag a { color: inherit; text-decoration: none; }
.msg-text { margin-top: 4px; word-break: break-word; }
.empty { padding: 40px 20px; text-align: center; color: var(--muted); font-size: 14px; }

/* flow */
.eyebrow { font-size: 12px; font-weight: 700; letter-spacing: 0.18em; text-transform: uppercase; color: var(--accent); }
.flow { margin: 8px 0 28px; }
.steps { margin: 14px 0 0; padding-left: 20px; color: var(--muted); }
.steps li { margin: 6px 0; }
.steps b { color: var(--ink); }

/* docs */
.docs { padding: 16px 0 40px; }
.docs h2 { font-size: 30px; letter-spacing: -0.01em; margin: 8px 0 8px; }
.docs h3 { font-size: 18px; margin: 28px 0 8px; }
.bullets { color: var(--muted); padding-left: 20px; }
.bullets li { margin: 5px 0; }
.code { background: var(--surface); border: 1px solid var(--line); border-radius: 12px; padding: 14px 16px; overflow-x: auto; font-family: "JetBrains Mono", monospace; font-size: 13px; line-height: 1.55; white-space: pre; }

/* banner */
.banner { background: #fff7ed; border: 1px solid #fed7aa; color: #9a3412; border-radius: 12px; padding: 12px 16px; font-size: 14px; margin: 4px 0 20px; }
.banner code { background: #ffedd5; word-break: break-all; }
.banner.ok { background: #ecfdf3; border-color: #bbf7d0; color: #166534; }
.lead.free { font-size: 15px; margin-top: 12px; }

/* chess */
.grid2 { display: grid; grid-template-columns: minmax(320px, 460px) 1fr; gap: 22px; align-items: start; margin-bottom: 24px; }
.boardwrap { display: flex; flex-direction: column; gap: 12px; }
.board2 { display: grid; grid-template-columns: repeat(8, 1fr); width: 100%; aspect-ratio: 1 / 1; border: 1px solid var(--line); border-radius: 12px; overflow: hidden; box-shadow: var(--card-shadow, 0 10px 30px rgba(10,10,10,0.06)); }
.sq { position: relative; border: 0; padding: 0; cursor: pointer; display: flex; align-items: center; justify-content: center; font-size: clamp(22px, 5.2vw, 38px); line-height: 1; }
.sq.light { background: #f1f1f4; }
.sq.dark { background: #c9ccd6; }
.sq.sel { box-shadow: inset 0 0 0 3px var(--accent); }
.sq:hover { filter: brightness(0.97); }
.pc { user-select: none; }
.pc.wp { color: #fff; text-shadow: 0 1px 1px rgba(0,0,0,0.45), 0 0 1px rgba(0,0,0,0.6); }
.pc.bp { color: #0a0a0a; }
.coord { position: absolute; font-size: 9px; font-style: normal; color: rgba(10,10,10,0.45); }
.coord.rank { top: 2px; left: 3px; }
.coord.file { bottom: 2px; right: 3px; }
.controls { display: flex; align-items: center; gap: 12px; }
.btn.ghost { background: #fff; color: var(--ink); border: 1px solid var(--line); }
.btn.ghost:hover { background: var(--surface); opacity: 1; }
.side .card { position: sticky; top: 76px; }
.side .board { max-height: 460px; }

/* footer */
.foot { display: flex; justify-content: space-between; padding: 28px 20px; border-top: 1px solid var(--line); color: var(--muted); font-size: 14px; margin-top: 20px; }

@media (max-width: 860px) {
  .grid2 { grid-template-columns: 1fr; }
  .boardwrap { max-width: 480px; margin: 0 auto; width: 100%; }
  .side .card { position: static; }
  .side .board { max-height: 300px; }
}
@media (max-width: 760px) {
  .grid { grid-template-columns: 1fr; }
  .hero { padding: 36px 0 20px; }
  h1 { font-size: 30px; }
  .lead { font-size: 16px; }
  .docs h2 { font-size: 24px; }
  .nav-links { gap: 14px; }
}
@media (max-width: 420px) {
  .wrap { padding: 0 14px; }
  .sq { font-size: 30px; }
  .controls { flex-direction: column; align-items: flex-start; gap: 8px; }
  .foot { flex-direction: column; gap: 6px; }
}

/* canvas */
.canvas { width: 100%; max-width: 460px; aspect-ratio: 1/1; border: 1px solid var(--line); border-radius: 12px; image-rendering: pixelated; cursor: crosshair; box-shadow: 0 10px 30px rgba(10,10,10,0.06); touch-action: none; }
.palette { display: grid; grid-template-columns: repeat(8, 1fr); gap: 6px; max-width: 460px; }
.swatch { aspect-ratio: 1/1; border: 2px solid transparent; border-radius: 8px; cursor: pointer; padding: 0; }
.swatch.sel { border-color: var(--ink); box-shadow: 0 0 0 2px #fff inset; }