Despite having his tongue planted in his cheek, developer Erik Wolpaw put things pretty clearly in an interview with Rock, Paper, Shotgun in which he described the origin of cake as the purported goal for test subjects:


Well, there are lots of message games coming out now. Like they’ve got something really important to get off their chest about the war in Iraq or the player is forced to make some dicey underwater moral choices. Really, just a whole heck of a lot of stuff to think about. With that in mind, at the beginning of the Portal development process, we sat down as a group to decide what philosopher or school of philosophy our game would be based on. That was followed by about fifteen minutes of silence and then someone mentioned that a lot of people like cake.

There are a few reasons that people might prefer Portal to a “message game” with “stuff to think about.” Sometimes people don’t want to think; they just want a new gun that shoots something radical, and to be trained in shooting something radical with their new gun. Actually, the gun in Portal allows you to do different types of abstract thinking and to encounter physics and combat tactics in a new way. So Portal isn’t a total reprieve from thought. It’s just a compartment for thought, an underground testing complex hermetically cut off from the world, purportedly message-free. Like a game wholly game, fluttering its empty sleeves, as Wallace Stevens might have said. (Note that Steve Meretzky, in his clever presentation praising Portal, didn’t actually say that the game is anything more than this; he just said that the game was a relief from the drudgery of life.) The decisions made to craft such a game are, of course, aimed at enhancing playability and amusement, at increasing sell-through. They cannot be based on any attempt to make the game more meaningful or to make it relate to life in a more interesting way. Even the most emotially charged sequence — the final, beloved one in which “Still Alive” plays as the credits roll — has a very simple primary “story” or “message” function: Leaving open the opportunity for a sequel.
So there are really two big ideas in these two games: The passage of a person through life and the idea that takes control by default in the other, supposedly message-free game, the passage of SKUs [he means dollars I guess? -ed] through retail stores.

In about ten years, I suspect that few people will engage with Portal unless they are being nostalgic or are specifically looking into the history of commercial video games. The game will probably have the status that the 1997 Mario Kart 64 has today. It will remain remarkable for its design, will be recognized for its technical accomplishments at the time, will still be fun at parties (an admirable quality for a single-player game), and, overall, will be seen as an interesting stepping stone to whatever evolves.

In about twenty-five years, on the other hand, I think Passage will have something of the status that the 1985 A Mind Forever Voyaging (by none other than Portal-praiser and recent GDC Game Design Challenge winner Steve Meretzky) does today. People will not play it at parties, certainly. But they will remember it because it showed them, for the first time, how games can model our world and what we care about in it. They will study it, modify it (recall that Passage is in the public domain) and build new games in response to it. They will play it for the first time and stop stunned, or cry, or imagine the reactions of all the others who have also gone through this miniature life.

Portal is neat, and its design accomplishments and high polish are real. It just isn’t the true heartbreaker of this pair of games. And, of the two, it also isn’t the game I wished I had developed.