A while back I did a number of 1970s Atari/Kee Games arcade games in VHDL, I finally got around to posting the code in one central place where I can update it as needed. These are not targeted to the Replay but porting them should be fairly trivial, I have kept them as platform agnostic as possible. Recently I pulled this stuff out again and started playing with it some more.

https://github.com/james10952001

I have a couple more than I'm working on, Sprint 4 and Subs, which I've gotten as far as getting the attract mode running however I'm running into some issues that I suspect are related to timing. I'm finding that making unrelated changes to the code breaks things, Subs for example currently runs fine *if* I have the SignalTap logic analyzer enabled and set to look at some specific signals, but otherwise it doesn't work at all unless I comment out the input code. When it does work, the player start LEDs just flicker randomly, along with all the other signals that come from that decoder. I had a similar issue with Ultra Tank but then it "magically" was fixed when I made some other tweaks. I'd like to refine my technique so that I'm writing better code and spending less time chasing down weird random issues like this. I suspect most of the trouble comes down to clocking, and using various signals as clocks instead of making everything truly synchronous, but I've had limited success trying to figure this out. Is anyone interested in looking over any of my code to help me clean it up a bit? I've released it all as open source with hopes that others will enjoy it. If I can get these cleaned up nicely then there are several more games I can do fairly easily as they share a lot of similar hardware.