Well, that is interesting.
As I understand, there is no "index out of bounds" error type supported by PBP?

I've modified that part of code to look like this:

Code:
if topline[x]=32 then a=0
if topline[x+1]=32 then b=0 'blanker


if X=>16 and botline[x-16]=32 then a=0
if x=>16 and botline[x-15]=32 then b=0
So far, works fine. Will keep you updated