This trait gives a Game Piece the capability
to be made invisible. Specify the key which the user will type to
make the piece invisible and the name for the command that will appear in
the popup menu. The visibility of the Game Piece can be defined
by three different means. It can be based on the Player, so only
the Player turning it invisible sees it. It can be based on the
Player Side, so all players that are on the same side can see
it. Or it can be made invisible for all but a given side.
The same command turns invisible piece visible
again. To those players to which the Game Piece is visible, the piece will appear
transparent against a background of the specified color. To other players it
will not appear at all. This trait actually only hides those traits
that are before it in the list of traits, so it should generally be the last
trait of a Game Piece.