Game runs fine for me and I really like the concept but the game needs some more moving things / moving enemies in general...
(Don't know if there are any already in this game, but doing all the first few level again after you die is kinda tedious.)
Right now I can plan ahead all the angles of attack in detail, not frantically smash buttons in order to evade coming attacks and kill enemies at the same time.
Oh and I died once by spawning right next to a spikey ball
Personally, I don't like the time slowing down when I activate my shield, but that could just be me...
I hope you'll continue to work on this