new layers (#483)

Content.Shared/Physics/CollisionGroup.cs

@@ -9,15 +9,16 @@ namespace Content.Shared.Physics
     [Flags, PublicAPI]
     public enum CollisionGroup
     {
-		None      = 0,
-		Grid      = 1 <<  0, // Walls
-		Mob       = 1 <<  1, // Mobs, like the player or NPCs
-		Fixture   = 1 <<  2, // wall fixtures, like APC or posters
-		Items     = 1 <<  3, // Items on the ground
-		Furniture = 1 <<  4, // Tables, machines
+		None            = 0,
+		Opaque          = 1 <<  0, // 1 Blocks light, for lasers
+		Impassable      = 1 <<  1, // 2 Walls, objects impassable by any means
+		MobImpassable   = 1 <<  2, // 4 Mobs, players, crabs, etc
+		VaultImpassable = 1 <<  3, // 8 Things that cannot be jumped over, not half walls or tables
+		SmallImpassable = 1 <<  4, // 16 Things a smaller object - a cat, a crab - can't go through - a wall, but not a computer terminal or a table
+        Clickable       = 1 <<  5, // 32 Temporary "dummy" layer to ensure that objects can still be clicked even if they don't collide with anything (you can't interact with objects that have no layer, including items)
 
         // 32 possible groups
-        MobMask = Grid | Mob | Furniture,
+        MobMask = Impassable | MobImpassable | VaultImpassable | SmallImpassable,
         AllMask = -1,
     }
 }