Tetris is a surprisingly addictive and compelling game, and it can leave attention-after-images (i.e., everywhere you look you see spaces and things that would/should be fitted just so into them).

We have a photo somewhere of me with the ninja girl as an infant on my lap, at the computer. I look like a diligent grad student, hard at work despite child! But in fact I'm playing either tetris or "mac man," Mac computer's version of Pacman.