The mechanic is so simple But hell it's fun to play, It got me hooked for a while. I think you can still expand this a lot more, For example, regarding the big blue ball I thought at first that if you hit it with the normal ball it would break the walls in a bigger way (since it is bigger) I think that would be fun that you can hit other objects (balls or something else) and those objects react and break more wall creating more destruction and giving the player more score. I think you have something that has some room to grow and develop some entertaining and creative gameplay. Great job