.container{max-width:800px;margin:60px auto;text-align:center;font-family:Segoe UI,Roboto,Helvetica,Arial,sans-serif}.board{display:grid;grid-template-columns:repeat(3,1fr);gap:15px;margin:30px auto;max-width:550px}.cell{width:100%;aspect-ratio:1 / 1;font-size:4rem;font-weight:700;background-color:#fff;border:3px solid #2c3e50;border-radius:12px;cursor:pointer;display:flex;align-items:center;justify-content:center;transition:all .2s ease-in-out;box-shadow:0 4px 6px #0000001a}.cell:hover{background-color:#f8f9fa;transform:scale(1.02);border-color:#3498db}.reset-btn{margin-top:25px;padding:12px 35px;font-size:1.3rem;font-weight:600;cursor:pointer;background-color:#2c3e50;color:#fff;border:none;border-radius:8px;transition:background .3s}.reset-btn:hover{background-color:#34495e;box-shadow:0 5px 15px #0003}@media(max-width:600px){.board{max-width:90vw;gap:10px}.cell{font-size:2.5rem}}