:root {
    --size: min(calc(100vh - 16px), calc(100vw - 15px));
    --square: calc((var(--size) / 9) - 8px);
    --thick: 5px;
}

body {
    font-family: sans-serif;
    background: white;
    color: black;
    margin: 0;
}

a {
    color: #005;
}

a:visited {
    color: #505;
}

table {
    border: none;
    border-collapse: collapse;
    border-spacing: 0;
    height: var(--size);
    width: var(--size);
}

td {
    font-size: calc(var(--square) * 0.85);
    border: 1px solid black;
    height: var(--square);
    width: var(--square);
    text-align: center;
}

.false td {
    border-color: red;
}

.column-2, .column-5 {
    border-right-width: var(--thick);
}

.row-2, .row-5 {
    border-bottom-width: var(--thick);
}

@media only screen and (prefers-color-scheme: dark) {
    body {
        background: black;
        color: white;
    }

    a {
        color: #aaf;
    }

    a:visited {
        color: #faf;
    }

    table, td {
        border-color: white;
    }
}

@media print {
    body {
        background: white !important;
        color: black !important;
    }
}