I’ve always been a fan of the demoscene work, as it pushes hardware to its absolute limits. You know those old consoles you played in the 80s and 90s? Well they were capable of so much more, if only the programmers had time to dedicate towards mastering the device. And that’s exactly what demoscene is.
This was (likely) all written in 68k assembly, as that is what the Sega Genesis required, however I know that there is also a C SDK available for the Genesis now as well.
Here’s some of the technical details on the Megadrive and how it was exploited in Overdrive 2, outlined in 27 pages.
Here are two videos from TITAN, dubbed Overdrive (2013) and Overdrive2 (2017).