*{margin:0;padding:0;box-sizing:border-box}body{font-family:Segoe UI,Tahoma,Geneva,Verdana,sans-serif;background:linear-gradient(135deg,#667eea,#764ba2);min-height:100vh;display:flex;justify-content:center;align-items:center;padding:20px}#app{width:100%;max-width:600px;background:#fff;border-radius:12px;box-shadow:0 20px 60px #0000004d;overflow:hidden}header{background:linear-gradient(135deg,#667eea,#764ba2);color:#fff;padding:30px 20px;text-align:center}header h1{font-size:2.5em;margin-bottom:10px}header p{font-size:1.1em;opacity:.9}main{padding:30px}#chessboard{display:grid;grid-template-columns:repeat(8,1fr);gap:0;margin-bottom:20px;aspect-ratio:1;background:#f0f0f0;border:2px solid #333}.chess-square{aspect-ratio:1;display:flex;justify-content:center;align-items:center;font-size:2em;cursor:pointer;border:1px solid #ddd}.chess-square.light{background:#f0d9b5}.chess-square.dark{background:#b58863}.chess-square:hover{opacity:.8}.chess-square:focus-visible{outline:3px solid #1d4ed8;outline-offset:-3px}.chess-square.in-check{background:#f99!important;box-shadow:inset 0 0 5px #b4000080}.chess-square.selected{background:#baca44!important;box-shadow:inset 0 0 5px #0000004d}#game-info{background:#f9f9f9;padding:15px;border-radius:8px;text-align:center;font-size:1.1em;color:#333}@media (max-width: 600px){header h1{font-size:1.8em}main{padding:20px}}