It was either I stopped at 6900 or 6700, mostly because the difficulty didn't really change after a while
Still, considering the limitations of this game, it's a pretty cool little game overall. I liked how the firing rate increased with the score though. I died more to my own bullets more than the other circles lol. Mostly because I was trying to re-aim myself somewhat after narrowly missing a shot.
I don't mean it to be a fault of the game though. I thought that was actually a pretty cool idea which added tension to the general gameplay. Also loved the wavey effect on the circle
All in all, good stuff