Very interesting concept!
Found it really difficult to keep the guy safe, but I guess that never was the point! :D
The main thing for me would be by far the movement of the "player".
And by "player" I mean the light source.
At the moment it has 100% acceleration and is thus bouncing around rapidly. And therefore so is the camera, making it all feel really jarring. I think it would instantly make the game feel much better if the light curved smoothly as it chased the mouse.
I would've also loved some ability to block projectiles. Projectiles constantly coming out of frame felt quite unfair. This would obviously need some balancing because If you could just block projectiles instead of going out to deal with the enemies that would be a very different game.
Also, the view feels kind of cramped. but just expanding the view wouldn't help as the character already feels kind of tiny. idk...
Just some of my thoughts, don't take them too seriously :)