It is sort of wild to me, as a child of the 90s, that the NES didn't really have graphics memory but read a specific region of the ROM bus to get graphics data, and so many animations would work in games specifically by bankswitching between frames. including the scrolling backgrounds in metal storm
for a fun time, open up a late NES that uses CHR-ROM like Metal Storm in a graphics editor like YY-CHR and press page up/down to count how much of the graphics data is dedicated to these kinds of animations