Hi,
Did you play in manual or auto?
I don't like manual controls, but I thin auto is really easy to catch:
Arrows for directions, one single X key to shoot, hard to be simpler

Only thing to get is, when you release X, your gun redirects toward the target automatically
Jakub (the dev) wanted to avoid the use of the mouse to aim at targets while moving with the keyboard
and to avoid to have 4 keys for directions and other 4 keys for the gun directions, he made it simple with one shoot button that redirects when released
How would you make it simpler?
For sure, aiming in a multidirectional or arena style shmup, is harder to consider than in a classic left to right horizontal one where shooting is always straight.
I think Jakub made fine!
What do you think about the other additions (bg music, weapons, bosses and achievements) ?