The main mechanic is a cool idea that fits with the theme. As previously stated, it was not very clear that enemies in their smallest form could be collected (maybe a color change could do the job). Also, I don't know if it is a bug but sometimes when I clicked on an enemy, it didn't hit him. The overall style is simple but nice and easy to read, the shader is a nice addition. I feel the waves are perhaps too numerous, or the difference in difficulty between them doesn't increase enough so the game feels a bit repetitive.