Psychological testing protocol

I've mentioned the game Portal 2 here before. It's something I enjoyed. I've also mentioned the trend for elaborate marriage proposals here before. It's something I mostly find nauseating. (Although as a divorce lawyer I have nothing against marriage, of course.) Well, here's something that combines the two - a marriage proposal within Portal 2:

(For those of you who don't want to go through the first two levels, or who simply don't have a clue what Portal 2 is all about and what the heck is going on, skip to 6 minutes 52 seconds for the final, explanatory, level.)

[Found on several sites. I can't recall which was the first, but Boing Boing was one of them.]