Variables
inlineread onlyNONE:Int = 0
Use this if you don't wish to perform any pre-collision sorting at all, or will manually sort your Groups.
inlineread onlyLEFT_RIGHT:Int = 1
Use this if your game world is wide but short and scrolls from the left to the right (i.e. Mario)
inlineread onlyRIGHT_LEFT:Int = 2
Use this if your game world is wide but short and scrolls from the right to the left (i.e. Mario backwards)
inlineread onlyTOP_BOTTOM:Int = 3
Use this if your game world is narrow but tall and scrolls from the top to the bottom (i.e. Dig Dug)
inlineread onlyBOTTOM_TOP:Int = 4
Use this if your game world is narrow but tall and scrolls from the bottom to the top (i.e. Commando or a vertically scrolling shoot-em-up)