It's annoying that the bonuses for higher accuracy mean some of the other upgrades can be harmful. I'd either make it so you click to fire (but can hold to fire as fast as possible), or make it so you can sell upgrades. Probably the second one. I like the effect of not having direct control of firing. A counter for how high your bonus is would be nice. I also think it would look a lot better if you added sprites for the gun aiming to the left and right.