If I draw too much, the game crashes, I discovered this when trying to draw two lines instead of one in an attempt to receive a better score :v
My only complaint is that the enemies appear very quickly at the beginning, there is barely time to 'see' the screen before the first one appears in the corner. Perhaps a preparation period of a few seconds would improve this point a lot.
Other than that, the game was very fun and interesting. Congrats!