Cool idea! I'd have liked some background music, and maybe some more elements, like perhaps spinning faster would push the other balls further, and to have some reason to even spin in a different direction, since currently spinning doesn't really impact much, just decides whether or not I am allowed to move. And anyway, the best strategy is to not even push the enemy balls to begin with, as standing in a corner lets you net lots of kills easily, since all the spawns are pretty far from the corners, you can wait there and the other balls start speeding up towards, and you can just dodge them and they will be unable to stop due to momentum and just fly off on their own. This can be mitigated by giving the player some kind of incentive to be inside of arena, like for example power ups!