The Homebrew game "pointless fighter" (https://youtu.be/PReg7pPcbIY) has graphics and animations substantially better than most of the MSX2 games.
Is there a technical breakthrough which permits such achievement?
How is it implemented?
I haven't looked at the code, but here's how I think it works: the Yamaha V9938 video chip supports 8 sprites of 16x16 full-color pixels per scanline. That's 128 pixels which is half of the screen width. But each fighter can be >64 pixels (4 sprites) wide, plus there might be a fireball on the same scanline, so you can't simply assign 3 sprites to each fighter plus 2 sprites to the fireball and call it done. Therefore, the clever part is managing those limited sprites in a way that minimizes visual glitches. Maybe if you play the game long enough and watch closely, you might see one.
I read through the thread pointed by a comment. It looks like: