I think you should be able to buy mutators only for yourself, I honestly hate mutators and it annoys me when someone buys bunny hop or something. Sometimes I buy low gravity for levels i absolutely hate but then everyone gets mad because it threw them off or something. This "buy for yourself" thing wouldn't be in effect for lengthen though, but that should prob just get removed. Invincibility just gets annoying because everyone just begs for it now. I think it's super op too and should prob cost more or get removed.