I've been hooked on a Palm game called "Hot Snake" lately, which has only one single button for control -- every time you hit it, the snake changes the direction in which it snakes along.

Which makes me wonder: Are there any other video games with a single button for control? Pacman had a single joystick, but you moved it in eight different directions. Pong had one spinner -- but you had two directions for spin. Gamelab's brilliant online game Loop uses mouse movement only (no button clicking) but again, it's omnidirectional movement. Is there another game in existence with only a single push-button control?