A stackable version of Tic-Tac-Toe! Pieces that nest inside each other allow you to cancel your opponent's move by playing over top of them!
A couple things I've found that add to the fun:
The Spinner also has a lid and can be used to house the play tokens for storage.
There is also a separate, optional storage case that holds the play tokens (if you print this, it MUST be printed in TPU - my print profiles account for this)