Fun entry! Controls were somewhat clonky, especially when a new zombie spawned (seems like you were not supposed to be holding any key until it actually spawned fully), but they were very responsive when it did work. The puzzles were fun, the level design was definitely good, and I liked the way you played with lightning.
Btw; I'm not sure if you intended for the zombies to be able to jump up the walls, but you could get rid of that by applying a Physics2D Material with both the settings set to 0 :D
Good job on your submission!