itch.io

I'm not familiar with Pico-8. I was stuck on flood fill as well. What I did was, when you completed a line, use the Qix area and find the nearest space (open area). Then do a flood fill from there using the shift-space character so it doesn't show, but still fills the screen. This separates the newly filled area which still contains space characters inside of it, from the shifted spaces. Then fill in the true space characters and do a quick swap of shifted back to true spaces. The source code should be in the download, otherwise I have it here.