Wolfenstein 3D and its '90s brethren Doom, have been modded for a number of unlikely devices, including a TI calculator and Canon printer. And in fact, Wolfenstein 3D was actually ported to the Game Boy Advance directly from the MS-DOS version.

However, this mod is on another level. Granlund used a breadboard to program the EEprom himself, then ordered a custom board, complete with pinouts. Using those, he added an NXP graphics processor, equipped with an ARM Cortex-M0 running at 48MHz. That chip is obviously more powerful than the Intel 386 CPU that originally ran Wolfestein on MS-DOS.

Once all that worked, Granlund ordered another custom board combining his original design and the NXP processor. After more tweaks, he ordered and received the final Rev. C cartridge, saying "everything works as expected and ... I didn't need any bodge wires this time around." The whole thing is, of course, powered strictly with the Game Boy Color's batteries.

The result is a game that plays amazingly smoothly on the 160 x 144 pixel screen, as you can see in the video above. A Reddit user perhaps sums it up best: "This is hella impressive. I mean, I'm absolutely in awe of the technical skill required to do this."