I like it. It's simple and not too easy or too hard.
However, the time based scoring is bad since drag and drop mechanics is very finicky. I find myself often to misplace pieces or miss the placement completely, which costs unnecessary time. This is very annoying when I know a solution and try to get a better score. At that point, I'm fighting only the controls.
Also, as others said, the difficulty is all over the place, with no difficulty curve.
Fix those points and this might be a full five stars.