This is really fun.
During the last minute, my hand was getting soar for spamming spacebar all of the time xD
I like this endless wave concept. Would have been cool to see another enemy type that can also shoot spells. I will say that this was difficult at first, because I have four crystals apart from each other and enemies coming from different directions. In other words, there was a little too much to pay attention to for the first two minutes of the game. Perhaps take it slow at first, then as time goes by go all out with the enemies.
But overall, I liked it.
Music is awesome, and the artwork is great!