Microbe runs so fast that it is almost impossible to play for any length of time. You control a 'microbe' - another name for a double-barrelled laser - using the 'Z' and 'X' keys to move left and right, and you can also move up and down using the and keys.
Firing is rapid and effective, using the opposition is nimble and numerous. The idea behind the game is that you have injected a microbe into the bloodstream of an alien, and your task is to use your firing button to polish off the alien's biological defences.
You start at the bottom of the screen, blasting the various anti-bodies as they approach, but when the ribosomes appear, you have to move up the screen to survive.
Here the problems begin since the action is so fast, the screen so crowded, and the explosive effects of each destroyed enemy so widespread, that telling exactly what's going on is very difficult.
Although the action is fast, noisy and colourful, Microbe is a frustrating game that is good to watch, but not much fun to play.