anchor.diff:  		source_turf.luminosity = Ceiling(light_range)
   		for(T in view(Ceiling(light_range), source_turf))
   			for (thing in T.get_corners(source_turf))
  -				if(!thing)
  -					continue
   				C = thing
   				corners[C] = 0
   			turfs += T
  
positive.code: 	LAZYINITLIST(effect_str)
  	if (needs_update == LIGHTING_VIS_UPDATE)
  		for (thing in  corners - effect_str) // New corners
  			if(!thing)
  				continue
  			C = thing
  			LAZYADD(C.affecting, src)
  			if (!C.active)
  
negative.code: 
  	L = effect_str - corners
  	for (thing in L) // Old, now gone, corners.
  		C = thing
  		REMOVE_CORNER(C)
  		LAZYREMOVE(C.affecting, src)
  