In the world of video-game
subplots, the one that
takes the cake (literally) is in
Valve's quasi-
FPS game
Portal. An interesting puzzle-oriented first-person experience, Portal takes place in a large clinical-looking facility called the
Aperture Science Enrichment Centre, with extensive facilities, observation rooms, hallways, and puzzle chambers. The puzzle chambers are the key to the game, as you use a provided space-warping "portal gun" to create
wormholes that allow you to move about from one place to another.
-minor spoiler follows-
The subplot is first manifested in a series of comments by the facility's AI, GLaDOS, who alternately threatens, compliments, advises, entreats, and promises cake at the end of the series of tests and challenges you find yourself trapped in. Eventually, you find graffiti and evidence of someone that lived for a considerable time as a rat in the walls of the facility. The graffiti waxes poetic about the cake, and how there is really no cake. The evidence of a long stay behind the scenes is shown by makeshift cookers made out of computer cases, improvised bedding, and other articles. The graffiti also provides an occasional clue to navigating the back-lot area of the test facitity.
-big spoiler follows-
Eventually, you find your way out of the facility and destroy(?) the mad computer running it. After the credits, you are finally shown that there is a cake before the game ends in a strangely touching scene. Interesting, compelling, quirky, and cute, the cake in Portal is a great example of the creativity of its design team, adding to the gameplay without actually being part of the game itself.