nice game, finished it and took a while. The most problematic achievement was my very last one. 2 min on 1 health. was pretty difficult but I managed by not killing any enemies so as to stay on a low score. The eye was beat the first round after I got the "eye always open" special.
It was inviting to get the achievements especially since your score went up fast after level ups.
Still the fact that you have to start from scratch is kinda tedious, its only the challenges that keeps it going.
the rainbow mode seemed of I mean I just bounced around the screen a lot. it didnt feel right.