Can't Stop [variant]

Can't Stop is an excellent three or four player "push your luck" game.

With two, Can't Stop suffers a bit from the board being too sparse (with just two players each competing for three columns). Here is the Can't Stop Can't Stop variant I learned from Don Woods (who learned it from someone else) for two players:

Play normally, except that A) the goal is to close 4, not 3, columns and B) a player is not allowed to stop on the turn they close their third column; at that point, they must either "win or bust", and try to close a fourth column as well.

This variant can also be played with 3 players, making for a brutal endgame, but a very interesting change of pace.