Just to close on The_S's idea, that is an alternative idea, but the highest yellow could not possibly be where it is because there would be no way you could stop it there (a yellow stop would mess it up, a red stop would match the reds, smart walls can't stop it there).
Puzzle It is my first real game. I'll keep updating Puzzle It. If you've suggestions for Puzzle It, you can post them here: Puzzle It : Tile Suggestions.