#42 added some info about doors and access levels

content/AccessLevels.md

@@ -0,0 +1,9 @@
+## Access Levels
+
+Doors can be restricted to certain access levels. The engine knows about 32 access levels (0..31).
+
+The names of the access levels are stored as [texts](../media/Texts.md) in chunk ```0x0879```. Per access level there
+are two text strings, so 64 in total. The first string is the short name, for example ```STD``` and the second the long
+name, ```Standard```.
+
+The first level (0) with name ```None``` is not checked. Doors with level 0 immediately open.

index.md

@@ -20,6 +20,7 @@
   * [Geometry](media/Geometry.md)
 
 * Content
+  * [Access Levels](content/AccessLevels.md)
   * [Electronic Messages](content/ElectronicMessages.md)
   * [Level Objects](levelObjects/index.md)
   * [Level Textures](content/LevelTextures.md)

levelObjects/10_Barriers/levelBarrierEntry.md

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+## Level Barrier Table (Class 10)
+
+```L20``` is a table describing barrier items.
+
+**Level Barrier Entry** (14 bytes)
+
+    0000  int16   Unknown
+    0002  int16   Unknown
+    0004  byte    Required access level
+    0005  byte    Unknown
+    0006  int16   Second door object index
+
+The ```Required access level``` indicates which [access level](../content/AccessLevels.md) the hacker needs to activate
+(open) the door. If zero, no special access is required. This values is ```0xFF``` for doors "locked by SHODAN level security".
+Such doors have a separate trigger referring these doors.
+
+The ```Second door object index``` refers to a second door to trigger when activating this one.
+Bulkhead doors for instance reference each other this way.
+