Returns the x position of the edge of the screen that is behind the player, in absolute stage coordinates.
Format: BackEdge
Arguments:
Return type: float
Error conditions: none
Notes:
This trigger is equivalent to the expression "ifelse(facing = 1, LeftEdge, RightEdge)".
Example:
trigger1 = Pos X + CameraPos X < BackEdge
; Triggers if the player is to the left of the back edge of the screen.