z {zmin} {zmax} {BGheight}
~Changes the location of stage boundaries.
~{xmin} is how high up entities can walk. It starts at the top and works down, so larger numbers mean less room. Defaults to 160.
~{xmax} is how far down the character can walk. It also goes down from the top. Defaults to 232.
~{BGheight} changes where the bottom of the background is drawn. Defaults to 160. By changing this value, you can make the background match an altered {xmin}.
~This can be set once per level. You can change it between two stages. If you need to change it during a stage, you should combine it with the "wall" command in the stage itself.
~You can spawn entities outside of this range, but once they enter the playing field they can't escape again.
