You can use this script as the main AI for a triggerzone,dynamic entity,whatever.
:ambience=0,ambiencered=0,ambiencegreen=0,ambienceblue=0
If you place one light marker in your level anywhere the level will be completely and totally black except for the area where the light marker is.
Some people have a tendency to make their games way too dark.
I don't have to be able to see everything but not being able to see at all and to bump into stuff gets old.
There are a variety of threads devoted to the subject of lighting and,to be honest,this has been covered quite a few times.
Please have mercy and use the search function.