body{font-family:Segoe UI,Tahoma,Geneva,Verdana,sans-serif;margin:0;padding:0;background:#f0f4f8;color:#333}h1{margin-top:20px;font-size:2rem}h2{margin:1rem 0;color:#4a4a4a}button{margin:0 .5rem;padding:.5rem 1rem;font-size:1rem;border:none;background-color:#3f51b5;color:#fff;border-radius:4px;cursor:pointer;transition:background-color .3s ease}button:disabled{background-color:#9fa8da;cursor:not-allowed}button:hover:not(:disabled){background-color:#303f9f}.grid-container{display:grid;justify-content:center;align-items:center;margin:2rem auto;width:fit-content;gap:5px}.grid-cell{width:60px;height:60px;background:#fff;border:2px solid #607d8b;display:flex;justify-content:center;align-items:center;font-size:1.5rem;font-weight:700;cursor:pointer;-webkit-user-select:none;user-select:none;transition:background .3s}.grid-cell:hover{background:#eceff1}