Amazing concept! I enjoyed trying to beat my high score and I loved how chaotic it got once a bunch of enemies started spawning in the arena. The graphics are fantastic, too. The most glaring issue is probably the lack of sound, and I also found that the leaderboard scene wasn't designed to adjust for different resolutions, so it looked stretched for me. I also think the game could benefit from a little more feedback when killing an enemy (maybe a +100 floats above their head?), and powerups that temporarily reduce your buildup time would help make the game feel more rewarding.