I went through it step by step, and I don't think that this is the best tutorial. Engine is quite buggy when you start to do your own changes and it's mechanism isn't explained well enough. Especially player movement.
I would add the HP for the players and all the enemies. Instant death is annoying. Lasers can fade about 10% after each bounce, and take less damage then. Nice game and great music. :) 5/5