Update roomtypes.md

docs/roomtypes.md

@@ -3,11 +3,13 @@ Room Types (in the `roomtype` object layer) affect how the camera scrolls. This
 
 ### Room types:
 ```
-0: no camera
+0: unused room. will be automatically to set to -1 if above a positive-valued room
 1: single room, no scroll
 2: horizontal room
 3: vertical room
 4: free camera room (can be used for horizontal, vertical, or open room)
 5: map transition room (draws an arrow in the minimap, connects with horizontal rooms)
--1, -2: not sure yet
+-1: Prevents the camera from entering a room from above or below (it can still enter from the sides)
+-2: Prevents the camera from entering a room from the left or right (it can still enter from above/below)
+-3: Prevents the camera from entering a room from any direction.
 ```