I ported a USB DisplayLink driver to the RP2040-based ISA PicoGUS card so I could use it to watch MS-DOS games make changes to the VGA palette in realtime. Specifically, I ported "libdlo" to use the TinyUSB stack in host mode, then spent way too much time optimizing it until it was sufficiently fast.
Awesome. I wonder if you could do something similar for a Sinclair ZX Spectrum, which not only did palette cycling, but since it only had character level (8x8) colors, had to time the changes to achieve per pixel colors. Timing might be tricky to deal with.
This kind of stuff is really interesting. Thanks for sharing, Ian! More please! :)
So cool.
Pitfall, The Mayan Adventure used color cycling in Windows 95 - you could update the DAC and Windows didn't (seem!) to mind.... Future Kinesoft games used identify palettes and just updated all the pixels, but for Pitfall, this helped the porting / emulation of the original console game color cycling.