Croquet

Croquet is a game of strategy, in theory simple - you just get your croquet balls through all the hoops in sequence. In practice, it's vicious. Your opponent can use his balls to roquet yours away from the hoops, in totally the wrong direction. So you might be sitting there, complacently leaning on your mallet, just in front of a hoop that you're ready to go through on your next turn, and your opponent is already through it with at least one of his balls and should be ignoring you.
It's his turn.
He doesn't ignore you.
He uses his balls to hit yours, the one you were about to put through the hoop and he sends your ball in totally the wrong direction, forward of the hoop, far away, and it's going to take you ages to get back, and now since he's hit one of your balls, he's allowed another turn. So he can move forward and you're left way behind.

I feel like my supervisor has just roqueted me. He's read and commented in detail on my cross-case analysis chapter, which is great, and I'm really pleased, but he's seriously questioning my conceptual framework, which means I have to do a lot of rethinking, then set out my arguments to address the issues he's identified, and it's going to take me ages.

Am I done yet?
No, so write well, (which is better than "No, and the requirements have changed" so throw it all out and start all over (See http://xkcd.com/844/))

And it isn't really croquet, because supervisor's not playing PhD anyhow. He's already through all his hoops.