Solid foundation and great art, but the gameplay leaves a lot to be desired. Because you can't really shoot and move at the same time and the enemies get incredibly overwhelming, the game incentivizes simply not interacting with the enemies whatsoever - I got to 5525 by just not shooting anything I didn't absolutely have to and only going for the pickups, which made the game a lot less fun (and also turned the game into a powerpoint - something to address the performance would be great). I think more diversity in enemy types and addressing the movement would do wonders. More enemy types could encourage different playstyles as the game goes on, and force you to change your tactics as you get bigger and bigger. As for movement, you could go for the Geometry Wars twin-stick approach, or you could try to elaborate on the current movement and combat to make it less punishing to play the game as was presumably intended. I think also providing some incentive to scale up in general would be great - all it really seems to achieve is additional health and the camera zooming out.
Great work overall, though! :)