hey bro, it's fun :)
but like the first comment mention, maybe it swamp so much enemy and effect to slow down the frame rate.
I have try lvl 6 and 200 point and the game almost drop to one frame ( i remember frame drop start at lvl 3 )
also I see another problem is bubble not on correct position, I have no idea why this happen but bubble always swamp at ~10 pixel upward of the character
additional info, played with linux, chrome
good try and keep up :)