Maybe could get harder a little quicker for me.
But more importantly I think you need to tweak the control just a little.
I like the way the ship moves out a little bit on key on then moves all the way on key off.
However, maybe I didn't understand, but it is not good that I am always committed to that move once key on.
I would sometimes like to cancel the fist key on and move in the opposite direction.
So a second key on in the opposite direction should cancel the first key on. and move a little bit to the opposite way.