Dresden Files: New York
A Zone is an abstract region of the space the conflict takes place in, an area in which two characters are close enough to interact directly (talk to or punch each other in the face)
|Same zone||can touch each other|
|Adjacent Zones away||can throw things at each other|
|One Zone away||can shoot at each other|
(some guns can shoot two or more zones away).
Any given conflict should not need more than a handful of zones. Considering that guns operate easily two zones away, two to four zones are sufficient for most scenes.