So much fun! It is hard to quick draw! You've done a really good job on seperating the procedure of shooting.
There's two things which should make it better:
1. Maybe add a arcade mode with increasing difficulties. That would be more challenging. Right now the impossible mode is just insanely hard.
2. In the third phase, setting the crosshair, it is a good idea to make the crosshair come back to the screen and bounce around. Right now, it is just one shot.