html,
body {
    margin: 0;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    background: #343541;
}

table {
    border-collapse: collapse;
}

td {
    width: 40px;
    height: 40px;
    border: 1px solid #666;
    padding: 0;
}

a {
    display: flex;
    width: 100%;
    height: 100%;
    justify-content: center;
    align-items: center;
    text-decoration: none;
    color: #fff;
    font-size: 24px;
}