Really good basis for the game, but a couple things I had issues with. I couldn't figure out what attacking was for, might have just been me though. Also, the store was pretty limited as mentioned by others before. If there were more things in the store and maybe some more areas for obstacles to be in, this would be an awesome game. Good job!
Simple, but good. It would be good if there could be a keyboard option instead of only a mouse one. Also, make it so the lines do not appear right where you are if you get a ball near the edge.
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