The alien with an "m" on it is the mother. The alien with an "f" on it is the father. Press the green flag to kill all aliens and start at the roots. The aliens will each create two new aliens every 5 seconds. I added the father alien to allow the population to exceed 302. The population (as far as I'm concerned) is unlimited. However, only 302 appear on screen at once due to Scratch limitations. Possible features in the future: Death of aliens Moving to different times (ex: seeing the population after 2000 years) Aliens producing random amounts of children