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AIs and other scripts can't see the map, so it would be useful if you could give them a hint as to what propulsion types will work best on your map.
An alternate approach has been suggested: propulsionCanReach()
VTOL_PATROL_X
AREA object where VTOLs should patrol if possible(between x1,y1 and x2,y2).
LAND_PATROL_X
Similar to above, but for land units.
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AREA object indicating to build walls within the contained tiles (if either height or width == 1) or build walls in a line between x1,y1 and x2,y2.
CHOKE_X
AREA or POSITION object indicating a choke point.
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