The game was easy to understand and easy to control. However, I felt that it didn't get harder as my points went up, and that it could quickly degenerate into spamming the button. I think the non-pink (I'm sorry I can't tell colours very well) alien provided some variety and did prevent the button mashing a bit, but it showed up too rarely to make a difference to the overall experience.
Otherwise, clean controls and straightforward mechanics.