:root{
  --bg:#f6f5f2;--fg:#1d1d1f;--muted:#76767a;--line:#e2e0db;--cell:#ffffff;
  --x:#2f6fed;--o:#e0533d;--accent:#1d1d1f;
}
@media (prefers-color-scheme:dark){
  :root{--bg:#141416;--fg:#ececee;--muted:#8d8d93;--line:#2a2a2e;--cell:#1c1c1f;--x:#6f9bff;--o:#ff7a64;--accent:#ececee}
}
*{box-sizing:border-box;margin:0;padding:0}
html,body{background:var(--bg);color:var(--fg)}
body{font:16px/1.5 -apple-system,BlinkMacSystemFont,"Segoe UI",Inter,Roboto,sans-serif;min-height:100vh;display:flex;flex-direction:column}
a{color:inherit}
header,main,footer{width:100%;max-width:440px;margin:0 auto;padding:0 20px}
header{display:flex;justify-content:space-between;align-items:center;padding-top:28px}
.logo{font-weight:700;letter-spacing:-.02em;text-decoration:none;font-size:20px}
.logo span{color:var(--x)}.logo b{color:var(--o)}
nav a{color:var(--muted);text-decoration:none;margin-left:16px;font-size:15px}
nav a:hover,nav a[aria-current]{color:var(--fg)}
main{flex:1;padding-top:32px;padding-bottom:32px}
h1{font-size:28px;letter-spacing:-.02em;margin-bottom:8px}
p{color:var(--muted);margin-bottom:14px}
.controls{display:flex;gap:8px;margin:20px 0 16px;flex-wrap:wrap}
.seg{display:flex;border:1px solid var(--line);border-radius:10px;overflow:hidden}
.seg button{background:none;border:0;color:var(--muted);padding:8px 12px;font:inherit;font-size:14px;cursor:pointer}
.seg button.on{background:var(--fg);color:var(--bg)}
.board{display:grid;grid-template-columns:repeat(3,1fr);gap:8px;aspect-ratio:1}
.cell{background:var(--cell);border:1px solid var(--line);border-radius:14px;font-size:clamp(40px,14vw,64px);font-weight:600;cursor:pointer;display:flex;align-items:center;justify-content:center;transition:transform .08s}
.cell:active{transform:scale(.97)}
.cell.x{color:var(--x)}.cell.o{color:var(--o)}
.cell.win{border-color:currentColor}
.status{margin:16px 0 8px;min-height:24px;font-weight:500}
.score{display:flex;justify-content:space-between;color:var(--muted);font-size:14px;border-top:1px solid var(--line);padding-top:12px;margin-top:16px}
.score strong{color:var(--fg);font-variant-numeric:tabular-nums}
.btn{background:var(--fg);color:var(--bg);border:0;border-radius:10px;padding:10px 16px;font:inherit;font-size:15px;cursor:pointer}
.btn.ghost{background:none;color:var(--muted);border:1px solid var(--line)}
.row{display:flex;gap:8px}
footer{color:var(--muted);font-size:13px;padding-bottom:24px}
.big{font-size:96px;font-weight:700;letter-spacing:-.04em;line-height:1;margin-bottom:12px}
ul{color:var(--muted);margin:0 0 14px 20px}