For those of you who don’t know, there’s a rather famous game called Portal. From the Wikipedia entry:

[…] The game primarily comprises a series of puzzles that must be solved by teleporting the player’s character and simple objects using “the handheld portal device”, a device that can create inter-spatial portals between two flat planes. The player-character, Chell, is challenged by an artificial intelligence named GLaDOS (Genetic Lifeform and Disk Operating System) to complete each puzzle in the Aperture Science Enrichment Center using the portal gun with the promise of receiving cake when all the puzzles are completed. […]

The portal device creates a red circle on one surface and a blue circle on the other, and you can walk into one and come out instantly on the other. This leads to some interesting curiosities, like walking through a portal and seeing yourself disappearing into the other one.

Now we come to the whole point of this entry, which is that a fan of the game has created a very neat Christmas tribute to it. Slightly late, I know, but I only found out about it last night.