body {
    font-family: Arial, sans-serif;
    background-color: #f0f0f0;
    color: #333;
    text-align: center;
    padding: 20px;
}

h1 {
    color: #007bff;
}

table {
    margin: 20px auto;
    border-collapse: collapse;
    width: 95%;
    max-width: 1200px;
}

th, td {
    border: 1px solid #ccc;
    padding: 10px;
    text-align: center;
    width: 30px;
    height: 30px;
}
        
th:first-child, td:first-child {
    text-align: left;
    width: 150px;
    font-weight: bold;
}

.cell {
    cursor: pointer;
}

.cell.checked::after {
    content: "X";
    color: #007bff;
    font-weight: bold;
}