awesome game! it would be incredible with multiplayer. I think some bosses would be cool, like you could chuck spongebobs friends in there either as multiplayer or as bosses. also the upgrade machine stops working after i used it twice.
I am at wave 42 and considering giving up as the only thing that can kill things is my wonderblaser, maybe add a new area with new guns and stuff to do. it 's getting pretty boring now.