table.outer {
    border: solid 2px black;
}

table.inner {
    border: solid 1px gray;
}

td.cujoku_cell {
    border: solid 1px gray;
    width: 1em;
    text-align: center;
    vertical-align: middle;
}

td.cujoku_init {
    border: solid 1px gray;
    width: 1em;
    text-align: center;
    vertical-align: middle;
}