How about a RED and BLACK ball!!!!!
Your concept is somewhat original, using a ball too pop balloons and another to collect coins that remain, but for God's sake, change the color of those balls man. Allow for it to not blend into the background. A light blue sky background and a light blue ball doesn't contrast. I found myself having to concentrate on the light blue ball and forgetting about the other one for fear of losing track of it.
PLEASE CHANGE THE COLOR!! 3/5-5/10