Thank you very much Earthborn!

I already knew about the Microsoft link to the problem which causes an error and other Microsoft pages about the PAINT statement.

I didn't know about the gwbasic site's information about the PAINT statement. It's by far the best description (however still not nearly as clear as it could be) of how the background string works that I've found. Although it didn't give me any new information as such, it clarified a lot of my research. I'm surprised I was able to deduce as much as I have correctly purely through investigation. I'm particularly happy it validated my observations that the background string only really defines one color.

One statement in the gwbasic site's info still baffles me:
"You cannot specify more than two consecutive bytes in the tile string that match the background attribute. Specifying more than two results in an "Illegal function call" error."
I can understand what they are saying and can make this error happen but my question is WHY this should cause an error? Any ideas?

Thanks again,
Galleon

PS. Now I can actually begin coding again!