Glad you liked it! We had thought about inputting more alternatives - such as repulsion effect you mentioned it but also things like slow motion bonuses, teleport-like worm-holes and stuff like that - but we had to account for the time we had (Which we got really close, like, 10 minutes before the mark if I'm not mistaken!). About the bullet predictability - yeah, we got that comment from others and although it seems to be precise mathematically maybe it's one of those things were it starts to hurt the game. We had not thought about forcing a distance from the center, which I think it's what you mean, so props - we may give it a shot in changing that afterwards.
Thanks for taking the time to give us input, by the way, we really appreciate it!