16-bit address and data buses? Hardware multiplier, divider, and barrel shifter? I wouldn't exactly call it simple. The cost to build one out of discrete logic probably approaches the quadruple digits.
Magic-1 (http://www.homebrewcpu.com/) is a 16-bit, microcoded homebrew CPU that took about 4 years to build, and it doesn't have any of the above features.
(I'm psychic: the next comment will ask who will implement a DCPU16 in Conway's game of life.)
Or maybe, you just wanted to have fun so you spent a night doing this. It isn't a big deal. If you don't waste one night of your life every once in awhile, you're pretty unlike the rest of humanity.
He loves Minecraft.
I'm dangling this game in front of him like a ball of twine in front of a kitten.
https://github.com/judofyr/rcpu
It's a DCPU assembler (written in a Ruby DSL) and an emulator/debugger (which allows you to step/run through the execution).
Next up I'm going to implement library support and write some I/O functions. Much of the code is already in place though (e.g. https://github.com/judofyr/rcpu/blob/master/examples/screen.... which maps 0x8000-0x8400 to the terminal).
