This software and "Garry Kitchen's Gamemaker" (both from Activision)
share the same background idea: a new language for games and graphics.

Three tracks of this disk can't be read with a standard DOS due
to an alterated address epilog. The usual $DE $AA was changed to
$DE $XX where $XX is different for each track.

We need to tell DOS to ignore epilogue to get a copy of the original disk:

POKE 47516,234 ($B99C:$EA)
POKE 47517,234 ($B99D:$EA)
RUN COPYA

Here the trick is that the modified bytes are used as keys to decode
the following data read from the disk.

Use a disk editor and look at:

track $00 sector $0A byte $3D change $85 $00 - STA $00
                                  to $EA $EA - NOP NOP
                     byte $5E change $EE $3E $9B - INC $9B3E
                                  to $20 $A2 $9B - JSR $9BA2

then write this little routine starting
at byte $A2:

A9 8B - LDA #$8B
85 00 - STA $00
A9 9C - LDA #$9C
85 01 - STA $01
A9 AD - LDA #$AD
85 02 - STA $02
60    - RTS

This put in the zero page the original modified ("original modified" is
an oximoron?) epilogue byte so the program can go on with the decoding step.