Overscan Demo border bug

[Alessandro1970]

Overscan Demo does not work:
OVERSCAN.zip

On ZxPoly:

On Fuse:

[Alvarez81]

What kind of check does the demo perform to verify if it is a spectrum or not?

[Alessandro1970]

I do not know what kind of check it performs, but there is a fixed version for pentagon and it run on ZxPoly (the check is bypassed I think).
This is the fixed file:
OVSCPFIX.zip

But borders do not work like in an original speccy, this is the video taken from original speccy about this demo:
https://youtu.be/Uw0ppGQkBs0