Played it through and it was fun! Controls are very smooth and intuitive. Even without the tutorial I figured out the controls within seconds.
Things you might improve:
- Right mouse button for aiming is not really necessary - could just aim all the time
- Enemies can easily be ignored - it is possible to run through to the boss without killing any enemy
- I did not understand the effect when the player turned red and was constantly loosing health. What did it trigger?
- The player can shoot through walls, the enemies cannot -> that can be exploited to kill the boss or other enemies
- The 4th weapon is a bit weird, it produces a huge glowing "thing" so that I cannot see anything else, and it seems not to do damage that is adequate to that effect :)
- I found it hard to dodge the shots of the multishot enemies, but on the other hand they do only little damage. You could try around with making them easier to dodge but increase the damage -> may make fights more tactical.