I also made a Cyclone II FPGA implementation :] It looked like this and supported very primitive line rendering:

https://github.com/niedzielski/swankmania/blob/master/DSC057... https://github.com/niedzielski/swankmania/blob/master/DSC057... https://github.com/niedzielski/swankmania/blob/master/DSC057...

Unfortunately, the physical hardware and later the code were both stolen in separate incidents. I was able to recover some version of the latter I had shared with a peer. It's posted in the same repo but probably not worth reviewing as it's from my college days and a total mess.