Considering you only made this in 3 days, I have to say, despite the crude graphics, it was really well put together! The game loop was complete, there was enough content to keep you interested and engaged, and I actually played till the end (beat it in 18 Earth days). I liked the 2 different systems - upgrading your turtles/cannon and reducing the number of Earthlings. Good game design, with more time, this would have been a top contender!