I downloaded the Android version because I have no MS Windows. (Linux version please?)
Regardless, this game is awesome, and stole an unknown amount of hours from my life immediately after installing it.
I want to offer some suggestions though; try using subtle shading to help with depth perception. The further away, the darker the colour temperature, the closer something gets, the closer the colour temperature gets to the player ship, and when they pass they reach the same colour. Look at my otherwise much simpler and less fun little game prototype thing I made in Scratch: https://scratch.mit.edu/projects/89719760/ Notice how I made the arches kind of fade in. In this case I used transparency to achieve the effect. The drawback of this that overlapping things in the distance makes it confusing which order they are in. But I bet you can figure out some shader magic.
Also, an easy mode where your bullet hit boxes are bigger would be nice, at least for the android version, my phone only has a 5.65 inch screen, and I am not very good with virtual touch screen controllers that has no haptic feedback. Or, Linux version please?
Maybe you could make a very subtle vibration that starts when your thumb gets off centre and gets bigger the further out on the virtual stick you are? With the max vibration on the edge being not much more than the on screen keyboard key press feedback.
