Creative but dull.
I enjoyed the idea but it could have been so much more. For starters, I think you should've added some fast paced audio. The graphics I liked, the background was detailed. I think you could've made different levels different colours and themes though. Maybe with the walls and balls suiting the certain themes. The sounds were nice and simple. I liked the idea I saw before of having a high scores. Either that or add checkpoints. Perhaps there should've been the abilty to start a wall, for say going downwards then to be able to made it go left or right, to make a small square in the corner or something, it would have made the game a bit easier and a bit more dynamic. Maybe you could add some power-ups too, it lacks a little variety. Overall, it was pretty fun, but got slightly boring after not too long.