table {
    border-collapse: collapse;
    width: 600px;
}

td {
    border: 4px solid black;
    padding: 0;
    width: 150px;
    height: 150px;
    text-align: center;
    font-size: 26px;
    font-family: 'Courier New', Courier, monospace;
    font-weight: bold;
}

main {
    margin: 0 auto;
    display: table;
}

.button-container {
    text-align: center;
    margin: 16px;
}

.button-container button {
    padding: 10px 20px;
    font-size: 48px;
    font-family: 'Courier New', Courier, monospace;
    font-weight: bold;
}

.error-container {
    text-align: center;
    font-family: 'Courier New', Courier, monospace;
    font-size: 26px;
    font-weight: bold;
    color: red;
}