CSS Grid without an explicit grid-template-columns defaults to a
single-column layout, so the 64-144 tiles stacked vertically and
the user saw a long column instead of an 8x8 (or 10x8 or 12x12)
battlefield. Set the column count via a CSS variable on the grid
root, written by match.js after the match snapshot loads (CSS attr()
for non-content properties is not yet shipped in Safari or Firefox).
Keith Solomon