Was looking through UFO Swamp Odyssey and saw that they had multiple sprites or sprite pieces per sprite tile. Like how they have 2 pairs of eyes in one sprite tile. And I'm completely clueless as to how they accessed the bottom half of the sprite. I know in the arguments for SPR() you can choose to only use a fraction of a sprite, but it always starts at the top left corner. So how did they only use the bottom half? I looked at the code for a good couple minutes but couldn't find anything and I don't know what this technique is called so I don't know what to search for.

there is another function that allows drawing any rectangle from the spritesheet to screen: https://www.lexaloffle.com/dl/docs/pico-8_manual.html#SSPR