Good, but needs improving.
The concept needs to be quite improved. Your title says racing, but I found no racing in the game. The idea was quite ridiculous because I don't believe anyone would throw tennis balls at hamsters. The game itself, however, was quite simple and somewhat entertaining. Would be used as a game to play when bored, but nothing too great. I would suggest improving the gameplay, idea, and maybe add a bit more detail. Otherwise, good game.