When you think about it, it's amazing this didn't pop up earlier.
Swedish programmer and enthusiast Anders Granlund has been working on a little pet project: getting Wolfenstein 3D to work on a Game Boy Colour. There's no way to actually just port a file of the game over, so he's had to build his own Game Boy cartridge from scratch.
The project started with an IO breakout cartridge, manufactured by the community printed circuit board website OSH Park. Granlund has been logging the entire build over at Happydaze.se, but you can see some work in progress footage below.
"The Gameboy has a clunky way of handling colours," Granlund wrote. "It has a total of 8 palettes of 4 colors each, and each 8×8 tile can be assigned to one palette. The KE04 tries to find the best matching palette for each tile. To reduce color errors I decided to make each palette mostly grayscale with a single accent colour. Each texture on the KE04 will use a single palette due to memory and performance reasons."
The latest cartridge supposedly has a grand total of 5kb (gasp) of room on the ROM. Just 3kb is enough to fit the remainder of Wolf 3D's levels, supposedly, so I'm curious to see what can be done with the remaining 2kb.