Editing RPG System Symmetries (section)

== Trivial Symmetries ==
Trivial symmetries are those that are so obvious they're not really worth mentioning. A couple will be listed as examples though, and the category might be of interest for those looking for ways of making their system particularly strange. I know of no current systems that do not exhibit these symmetries. (These also tend to be symmetries that exist in the real world.)

===Frames of reference===
Systems should not change between different frames of reference with the same overall acceleration. That is, nothing mechanical should change between the frame of reference inside a moving train (on a straight level track) and the frame of reference inside a stopped train. (Note that a stopping train has a different acceleration to the other two.)

===Time===
Systems should not change between two moments in time. That is, anything that works mechanically now, should work the same in any other time, assuming the situation was otherwise identical.