The game takes place inside a bacteria factory. You walk around and spray the various bacteria with yeast. That will turn them into white happy cloud-like bacteria. If you spray them again they will turn malevolent, so make sure not to overdo it! Move all the happy bacteria to the little bottle to clear the stage.
Much alike the Universal arcade game Space Panic. You control a character with a shovel and dig pits in hope that the aliens chasing you fall into them. When they do you need to hit the alien with your shovel to kill it.