I've been thinking about **printing** a tic-tac-toe where you
zoom in on a cell to see the results of having chosen to play in that
cell: a full game tree rendered in nested form. This SVG shows the
beginnings of what that would look like, although I wrote it by hand
as an experiment in getting it to look right, so it doesn't have
everything filled in yet.

The game is only nine moves long at most, of which only four are chosen by the second player, so you need only four levels of nesting if "the computer goes first". That's a linear scale reduction of about 3⁴ = 81, or a little more than that to allow some whitespace around the edges, say 100. If you want the smallest boards to be at least 15 points tall, so that people can see them, then the big board needs to be about 1500 points tall, or 53 cm or 20.8 inches. A4 paper is 210 mm × 297 mm, so printing out 530 mm × 530 mm would need six sheets of A4 paper in a 2×3 arrangement. If "the human goes first" then you need three times that, like 1½m×1½m.