Andrew Carol's Lego Difference Engine is a low tech computer after Babbage's nineteenth century mechanical computer designs. This can evaluate any polynomial of the form ax^2 + bx + c, to three digits of precision, with an effort of a hundred or so turns of the crank.
dead link: http://acarol.woz.org/
"Your nasal hair speaks volumes concerning the Isle of Wright."
Lots of technical information on this dead-end game platform. This is one of those things that I didn't let slip past me, like the PXL-2000. Instead I found it being remaindered and picked up the device, all the accessories, and all the games the store had for about a hundred bucks. The two main drawbacks I see in this design are the monochromatic display and it is impossible for someone to watch you play. Even with a Gameboy you could watch over someone's shoulder.
qz thoughts