Aiming with the mouse pointer was something I considered, but I never bothered to implement it. I'll try it out now, but a lot of the difficulty comes from the fact that you have to aim manually, so the enemies would have to be tweaked as well.

No incentive for not shooting is a characteristic of many Shoot-em-ups, so I don't consider that a big problem, but I'm probably going to make it so that the bird shoots automatically. Having to hold RMB gets pretty tiring after a while.

Thank you for your feedback!