Some weird "push-the-graphics-limits" feats I'm pretty impressed by:
1982 IBM CGA adaptor doing 1024 colors
Why it's so impressive:
The CGA could only do 4 colors in graphics mode. But this demo manages to blow the VGA adaptor away with some insanely clever trickery. Remember CGA? That was before EGA, and way before VGA. The audacity to push a CGA beyond VGA, in a demo.
Link: The 8088 MPH Demo
Super Mario for Commodore 64
Why it is so impressive:
In 2019, someone finished an ACTUAL PORT of Super Mario for Nintendo. Mario for Nintendo, to the Commodore 64 computer. A system running on a slower CPU that had only 8 sprites (the Nintendo has 64 sprites with a hardware multiplexor). The Commodore port was using an impressive software-driven(on a 1MHz CPU) 48-sprite multiplexor and a very unusual VSP scrolling trick, and a software-emulation(on a 1Mhz CPU) of the Nintendo sound. Even many of the original Super Mario hacks on the real Nintendo, actually works on this port -- including many old 1UP tricks and level-jump tricks; such an uncannily near-perfect port onto a slower 8-bit computer. Much of the original 6502 code was literally copy and pasted from NES ROM to the Commodore 64 port, with hand modifications only where necessary. It took 7 years to port and the result was so masterpiece, that it received a DMCA takedown by Nintendo.
Link: Lemon64 Forum Thread
I have some personal feats, probably not as impressive as the above, but included anyway because most people who are interested in "these tricks" are also interested in some little-known feats I've done, too.
The commodore 64 computer is the platform I cut my teeth on. Back in 1986-1991 I actually had a hobby programming a Commodore 64 -- I actually personally (Chief Blur Buster) programmed a Uridium clone in 100% 6502 programming in SuperMon64. Here's my old Lemon64 forum thread
Occasionally, I still play with raster interrupts from time to time. They're still sorta possible to do on modern GPUs in a coarse way: In fact, I believe that I'm the world's first person to pull off a real-time-raster Kefrens Bars demo on a GeForce/Radeon
through the "VSYNC OFF tearlines are rasters" trick. Derivatives of this research are is now used as a lagless VSYNC mode in WinUAE Amiga emulator
to synchronize the emulated raster with the real raster (even on high-Hz and VRR displays too).