@sun I'm not very familiar with GBA programming, I've programmed a DS game, which I was told the 2D mode acted quite a bit like a GBA, though I'm not sure how true that is. But I only did pretty basic stuff with it.
I'll have to watch the video you shared about it, but my first impression is that the throughput of updating it before a redraw would be tough to manage on a GBA. But if that's what they're using, I guess they found a way.