From the NannyMUD documentation

LAST CHANGE

2003-03-28

FUNCTION

NAME
        add_light - Add to the light level of an object.


LOCATION
        /obj/light (Inherited by most lib objects)

SYNTAX
	void add_light(int level)

DESCRIPTION
	An object is by default dark. It can be set to not dark by calling
	add_light(1). This will in turn affect the light of the environment
        as well.
   
	You can set the object to be 'more than dark' by using negative
	values or extra bright by using more positive values.


NOTE
	There is no point in doing add_light(0). If you want an object
	(usually a room) to be dark, simply do not call this function.
        The default light level is 0.


EXAMPLE
	add_light(1) 
	  Make this object somewhat brighter.

	ob -> add_light(1)
	  Increases the light level of ob by 1.

	add_light(-query_object_light())
	  Cancels out the local light in the current object.


SEE ALSO
        query_light in sfun/query_light


SEE ALSO
        query_object_light in sfun/query_object_light