I second that.
I beat Portal 2 yesterday, goodness me what a challenge it was! I ended up resorting to Youtube 3 times on my play through
I actually managed to defeat
Wheatley by a complete accident, I was at the very end of the fight where you are lying on the floor with the portal gun in your hand, I saw the moon and I thought just for the hell of it that I would shoot the moon, I had no clue that it was how you defeat Wheatley, made me chuckle.