You could also try to expand on your points...
Why did you feel that the game was gimmicky? They did quite a few things with the portals and many puzzles had multiple solutions.
It being too short is obviously a personal preference and not an objective criticism, the story was wrapped up and you can't argue about the value since it was $20/free.
EDIT: Obviously you're free to dislike it and I'm not trying to change your mind, but if you want to criticise it, back up your arguments.