ScreenEdgeBuffer,NPC ID,UDLR Border,BUFFER SPACE,-,Active time,-
Keeps NPCs from leaving the screen. NPC ID is which type of NPC will be effected. UDLR (Up Down Left Right) is which border of the screen the npc won't be able to pass.
0 = Top 1 = Bottom 2 = Left 3 = Right
BUFFER SPACE is how close the NPCs can get to the edge before being stopped.
If you increase the BUFFER SPACE to a large amount, you can force NPCs to stay in certain parts of the screen. For instance a Lakitu that can't leave a small box area in the middle, or an NPC that can only be on the right side of the screen.
// Make it so Lakitu can't go off the left side of the screen (SMB1 style) // (stops him at 1 pixel from the left edge) ScreenEdgeBuffer,0x011C,2,1,0,0,0