Weird how the brain works. I experienced the same thing when Avril and I use to stay up and play Dr. Mario on the N64 together. I could see piles of pills lining up as I drifted off to sleep.
I used to have an old school Gameboy with Tetris when I was in high school. I played the crap out of that game. I can vividly remember the game, but not how the first girl I kissed looked. That sounds odd, but do you know what I mean? I'm rambling.
I just read about the "Tetris effect" on Wikipedia. Here is the article:
The Tetris effect is the ability of any activity to which people devote sufficient time and attention to begin to dominate their thoughts, mental images, and dreams. It is named after the game of Tetris, which requires the player to rotate and move falling blocks of different shapes to create, and thereby eliminate, complete horizontal lines of blocks.
People who play Tetris for a long stretch of time may be subsequently involuntarily prompted to think about ways different shapes in the real world can fit together, such as the boxes on a supermarket shelf or one's home furniture. This was parodied in The Simpsons episode Strong Arms of the Ma. They may also see images of falling tetrominos at the edges of their visual field or when they close their eyes. They may also dream about falling Tetris shapes when drifting off to sleep.
The Tetris effect can occur with other computer games involving prolonged exposure to sequential images, with any prolonged visual task (such as classifying cells on microscope slides, weeding, picking fruit, assembling burgers, or even playing chess) and can also occur in other sensory modalities. For example, in audition there is the tendency for a catchy tune to play out unbidden in one's mind (an earworm). In kinesthesis, a person newly on land after spending long periods at sea may move with an unbidden rocking motion, having become accustomed to the ship making such movements (known as sea legs or mal de debarquement).
Stickgold et al. (2000) have proposed that the Tetris effect is a separate form of memory, likely related to procedural memory. This is from their research in which they showed that people with anterograde amnesia, unable to form new declarative memories, reported dreaming of falling shapes after playing Tetris during the day, despite not being able to remember playing the game at all.
Maybe I'm not so weird after all.
P.S. Sorry to hear about Ryzom on the chopping block. The game scored high on innovation, but couldn't complete against the big MMOs.