That's the point though...have you played games with boulder puzzles?
Also have you played it? Because I have a feeling you might need to go from the sides or at least it's a different option.
Edit: the way I look at it is that you can get in three ways, assuming you can't move the boulders off of the blue space. There's supposed to be more boulders needed anyways for these types of puzzles. It's probably not supposed to be difficult.