I'll start off by saying this game isn't for everyone x)
I tried to make a game in one day, and wound up stumbling onto a mechanic I think is pretty damn sweet. A new martian spawns each time you make it successfully to the ship, and all previous martians spawn, in the exact same place as last time. This forces the player to constantly modify his route/strategy.
My mind was especially blown the later levels (20+) where you are forced to experiment and travel super intricate paths to freedom.
tl;dr I love this game, I hope you do too but you don't have to
P.S. Thank you adamatomic for flixel, it is badass.