Entertaining game
Some achievements seemed to be flawed when I was playing... I went for the "complete with no armor" one, and in the middle of the game, though I did not spend any point in armor, I got the "max armor" achievement, and did not get the one I wanted, even though in the upgrade screen, I did not have any point in armor (I did not get the "complete the game with level 6 armor" either, strangely)
The same applies to the health that I had completely upgraded, but I did not obtain the achievement.
Aside from that, I love it :) I like achievements, but they are usually just a plus. I enjoyed the concept and the way you have to dodge some enemies with a special pattern while you try to dodge others who move a totally different way, adding a strategical dimension :)