Interesting concept. I found the initial levels (1-1 through 1-20) too easy, solving them in under 20 seconds. After this I was bored, but there's no menu to allow you to jump to a more difficult level, or even to see how long a level is. (Do I have to go to 1-30, or 1-50, or 1-100?). I didn't want to wait around to find out.
I did notice that it was getting a bit harder to solve the next six levels. Sometimes the timer moved past the third star, but I still got awarded a third star. This needs to be fixed.
I didn't need any of the power ups, and wondered why you would.