After making some very simple 4 and 8-bit processors in Logisim, I was getting frustrated at the difficulty of exploring processor designs - making changes required a lot of tedious rerouting and reconnecting and I wouldn't be sure an idea would even work. @neauoire had much better results starting with a VM, and so I decided to give it a try.
The design goal is to come up with a fairly simple, idiosyncratic machine that encourages low res 3D graphics. While a general purpose computer can obviously render 3D graphics, I wouldn't say it's encouraged by the design in the same way the NES encourages sprites and tilemaps. I'd also like to design the system so it's features and limitations lead to a distinctive and recognisable style.