Looking at the Level 9 interpreter sources from https://github.com/DavidKinder/Level9 https://github.com/DavidKinder/Level9 it looks like the pre-bitmap games s

Looking at the Level 9 interpreter sources from https://github.com/DavidKinder/Level9 https://github.com/DavidKinder/Level9 it looks like the pre-bitmap games stored their images as little bytecode programs (with instructions for move, draw, fill, etc, plus a gosub opcode so you could have "draw the same complex shape several times", opcodes for reflecting and scaling, etc) -- check the getinstruction() function in level9.c. So likely hand-composed, not generative algorithm, I think.