Keep It Up! (1970)

This is an interesting cooperative play game with play as a solo game or a coop game of two people. There are 2 corkscrew sticks which you connect together and a propeller spinner that falls down this corkscrew. You can adjust the fan blades to adjust the speed of the propeller as it "falls" down the corkscrew sticks. (Basically you are adjusting how much resistance the air is making against the blades.) The game is played by not letting the propeller fall off the end of a stick; as the propeller goes from one stick to another, the top stick is moved to become the new bottom stick. When playing with two people, one person is responsible for moving the stick, while the other is responsible for the stability of the stick the propeller fan is currently on. If you are playing solo, you have to try and do both of these functions, which would be very difficult.