A while ago, with the Raspberry Pi still new, a fair amount of people decided to take one and stick it in the housing of a Game Boy. Usually, these things were somewhat reminiscent of a Game Boy, but pretty recognizable as products of a later time: they had more buttons to accommodate game consoles that needed it, they all had fancy backlit color TFTs and they ran off modern LiIon batteries. But what if you wanted to go for a more authentic mod? Let me introduce the DMGPlus.
In a nutshell, Sprite_tm replaced the original motherboard with one carrying an ICE40 FPGA and a Pi Zero, allowing the hardware to take a regular cartridge and emulate it as if you were playing off the cartridge. But you can also use a non-Game Boy cartridge and the Pi will run its bespoke script.
And yes, that means it can run Doom.