Too Easy.
It was a good idea, and well implemented - a simple design, simple graphics, and yet enjoyable. However, I found the game far too easy - there was little difficulty. It presented little challenge, and if the game had been any longer I am sure my interest would have quickly waned.
tl;dr - Good effort, good idea, too short, too easy.
7/10 - +2 gameplay, +2 idea, +1 graphics, +1 fun factor