Fun idea, though greed makes the game pretty trivial, at round 20 I was getting 250 pixels/kill and the only reason I didn't win is that the game crashed from there being too many squares on screen.
Moving around didn't really feel incentivized in any way though, so I never really interacted with the main gimmick. I felt like since there was only so much screen room and no way to change the camera other than moving, that if I walked to the left I'd take damage from the right just because I can't see over there.
Also the game very quickly becomes just spam clicking, the shots should probably auto fire when holding down the fire button.