It is somewhat mind blowing that the original version of the demo game was done with ridiculously rudimentary logic gates. If you haven't read the history of how Wozniak did this with little over 40 chips, you should look it up.
And yes, I realize the graphics are different. Probably even the game play.
At UC Berkeley one of the classes (EECS150) focused on creating an old-school arcade game in an FPGA using (virtual) logic gates. It is one of the best classes I ever took and really gives you an understanding of how these things were possible. It seems impossible when you first see it, but by the end it all clicks and you realize how much is possible in pure silicon.
Not who you're replying to, but there's a similar class at Cambridge where you implement pong/game of life on an FPGA board. Some of the practical course notes are available publicly, though the full computer design notes referenced are not. There may be some interest in the basic sources and approach however: http://www.cl.cam.ac.uk/teaching/0910/ECAD+Arch/
(Linked to the course I know from a few years ago, the course has since changed)
And yes, I realize the graphics are different. Probably even the game play.