A very fun and simple game. I like the clean retro graphics. However I think the difficulty increases too slowly. I think there should be eventually multiple laser beams at the same time to make it more challenging.
Also, I noticed you should bullets downwards while jumping. Do they have any function? I expected that I can shoot stuff with them. Maybe it would it be interesting if you made alternative balls that can only be harvested by shooting bullets at them?
Overall, well done!