Reverse Step

After the user has created a Petri Net Design, he may begin
simulation using either Forward Step, or Run.

After the simulation has progressed in this manner for at
least one simulation step, the Reverse Step can be used.

The number of Reverse Steps that can be performed is limited by
the History Size, which can be changed under the Options Menu.

Also, you may only Reverse Step the number of Forward Steps
that were performed, so the design will stop at the initial marking.
