diff --git a/OpenRa.FileFormats/FieldLoader.cs b/OpenRa.FileFormats/FieldLoader.cs
index f5f1b1616f..ab521d305c 100644
--- a/OpenRa.FileFormats/FieldLoader.cs
+++ b/OpenRa.FileFormats/FieldLoader.cs
@@ -11,7 +11,8 @@ namespace OpenRa.FileFormats
 			foreach (var x in ini)
 			{
 				var field = self.GetType().GetField(x.Key.Trim());
-				field.SetValue(self, GetValue(field.FieldType, x.Value.Trim()));
+				if( field != null )
+					field.SetValue(self, GetValue(field.FieldType, x.Value.Trim()));
 			}
 		}
 
diff --git a/OpenRa.FileFormats/FileSystem.cs b/OpenRa.FileFormats/FileSystem.cs
index 387023aa39..5d015acddc 100644
--- a/OpenRa.FileFormats/FileSystem.cs
+++ b/OpenRa.FileFormats/FileSystem.cs
@@ -27,6 +27,10 @@ namespace OpenRa.FileFormats
 			FileSystem.Mount( new Package( "speech.mix" ) );
 			FileSystem.Mount( new Package( "allies.mix" ) );
 			FileSystem.Mount( new Package( "russian.mix" ) );
+
+			FileSystem.Mount( new Package( "temperat.mix" ) );
+			FileSystem.Mount( new Package( "snow.mix" ) );
+			FileSystem.Mount( new Package( "interior.mix" ) );
 		}
 		
 		public static void MountAftermathPackages()
diff --git a/OpenRa.FileFormats/Walkability.cs b/OpenRa.FileFormats/Walkability.cs
index a94045b6f2..ef9426ff37 100644
--- a/OpenRa.FileFormats/Walkability.cs
+++ b/OpenRa.FileFormats/Walkability.cs
@@ -6,7 +6,7 @@ namespace OpenRa.FileFormats
 {
 	public class TileTemplate
 	{
-		public int Index;
+		public int Index; // not valid for `interior` stuff. only used for bridges.
 		public string Name;
 		public int2 Size;
 		public string Bridge;
@@ -36,10 +36,11 @@ namespace OpenRa.FileFormats
 							p => int.Parse(p.Key.Substring(8)),
 							p => int.Parse(p.Value)),
 					Name = section.GetValue("Name", null).ToLowerInvariant(),
-					Index = int.Parse(section.Name.Substring(3)),
 					Bridge = section.GetValue("bridge", null),
 					HP = float.Parse(section.GetValue("hp", "0"))
 				};
+				tile.Index = -1;
+				int.TryParse(section.Name.Substring(3), out tile.Index);
 
 				walkability[tile.Name] = tile;
 			}
diff --git a/OpenRa.Game/Game.cs b/OpenRa.Game/Game.cs
index e9e2f4db2e..5d5b393c90 100644
--- a/OpenRa.Game/Game.cs
+++ b/OpenRa.Game/Game.cs
@@ -46,7 +46,6 @@ namespace OpenRa
 			Game.changePending = false;
 			Game.mapName = mapName;
 			SheetBuilder.Initialize(renderer);
-			SpriteSheetBuilder.Initialize();
 			FileSystem.UnmountTemporaryPackages();
 			Timer.Time( "reset: {0}" );
 
@@ -71,8 +70,8 @@ namespace OpenRa
 			Timer.Time( "SeqProv, viewport: {0}" );
 
 			skipMakeAnims = true;
-			foreach (var treeReference in Game.world.Map.Trees)
-				world.CreateActor(treeReference.Image, new int2(treeReference.Location), null);
+			//foreach (var treeReference in Game.world.Map.Trees)
+			//	world.CreateActor(treeReference.Image, new int2(treeReference.Location), null);
 			Timer.Time( "trees: {0}" );
 			
 			world.LoadMapActors(Rules.AllRules);
diff --git a/OpenRa.Game/Graphics/SpriteSheetBuilder.cs b/OpenRa.Game/Graphics/SpriteSheetBuilder.cs
index 3b168da665..b7054962ff 100644
--- a/OpenRa.Game/Graphics/SpriteSheetBuilder.cs
+++ b/OpenRa.Game/Graphics/SpriteSheetBuilder.cs
@@ -6,13 +6,19 @@ namespace OpenRa.Graphics
 {
 	static class SpriteSheetBuilder
 	{
-		public static void Initialize()
+		public static void Initialize( Map map )
 		{
+			exts = new[] {
+				"." + map.Theater.Substring( 0, 3 ).ToLowerInvariant(),
+				".shp",
+				".tem",
+				".sno",
+				".int" };
 			sprites = new Cache<string, Sprite[]>( LoadSprites );
 		}
 
 		static Cache<string, Sprite[]> sprites;
-		static readonly string[] exts = { ".tem", ".sno", ".int", ".shp" };
+		static string[] exts;
 
 		static Sprite[] LoadSprites(string filename)
 		{
diff --git a/OpenRa.Game/World.cs b/OpenRa.Game/World.cs
index 43e2d4c670..c3fb15b429 100644
--- a/OpenRa.Game/World.cs
+++ b/OpenRa.Game/World.cs
@@ -56,9 +56,8 @@ namespace OpenRa
 
 			Map = new Map( Rules.AllRules );
 			Timer.Time( "new Map: {0}" );
-			FileSystem.MountTemporary( new Package( Map.Theater + ".mix" ) );
-			Timer.Time( "mount temporary packages: {0}" );
 			TileSet = new TileSet( Map.TileSuffix );
+			SpriteSheetBuilder.Initialize( Map );
 			Timer.Time( "Tileset: {0}" );
 
 			BuildingInfluence = new BuildingInfluenceMap( this );
diff --git a/SequenceEditor/Program.cs b/SequenceEditor/Program.cs
index ad668bddd6..1059ccc730 100644
--- a/SequenceEditor/Program.cs
+++ b/SequenceEditor/Program.cs
@@ -76,8 +76,6 @@ namespace SequenceEditor
 			}
 			catch( FileNotFoundException ){}
 
-			FileSystem.MountTemporary(new Package("temperat.mix"));
-
 			XmlFilename = args.FirstOrDefault( x => x.EndsWith(".xml") ) ?? "sequences.xml";
 			Doc = new XmlDocument(); 
 			Doc.Load(XmlFilename);
diff --git a/templates.ini b/templates.ini
index b3d10064a0..990bc437a4 100644
--- a/templates.ini
+++ b/templates.ini
@@ -2835,8 +2835,825 @@ tiletype19=2
 tiletype23=2
 tiletype24=2
 
+
+; interior tiles
+
+
+;;;;;; the interior `clear` tile is incompatible with the temperat/snow ones.
+;[INT_clear1]
+;Name=clear1
+;width=1
+;height=1
+;tiletype0=7
+
+[INT_arro0001]
+Name=arro0001
+width=1
+height=1
+tiletype0=0
+[INT_arro0002]
+Name=arro0002
+width=1
+height=1
+tiletype0=0
+[INT_arro0003]
+Name=arro0003
+width=1
+height=1
+tiletype0=0
+[Blah]
+Name=arro0004
+width=1
+height=1
+tiletype0=0
+[INT_arro0005]
+Name=arro0005
+width=1
+height=1
+tiletype0=0
+[INT_arro0006]
+Name=arro0006
+width=1
+height=1
+tiletype0=0
+[INT_arro0007]
+Name=arro0007
+width=1
+height=1
+tiletype0=0
+[INT_arro0008]
+Name=arro0008
+width=1
+height=1
+tiletype0=0
+[INT_arro0009]
+Name=arro0009
+width=1
+height=1
+tiletype0=0
+[INT_arro0010]
+Name=arro0010
+width=1
+height=1
+tiletype0=0
+[INT_arro0011]
+Name=arro0011
+width=1
+height=1
+tiletype0=0
+[INT_arro0012]
+Name=arro0012
+width=1
+height=1
+tiletype0=0
+[INT_arro0013]
+Name=arro0013
+width=1
+height=1
+tiletype0=0
+[INT_arro0014]
+Name=arro0014
+width=1
+height=1
+tiletype0=0
+[INT_arro0015]
+Name=arro0015
+width=1
+height=1
+tiletype0=0
+
+[INT_flor0001]
+Name=flor0001
+width=1
+height=1
+tiletype0=0
+[INT_flor0002]
+Name=flor0002
+width=1
+height=1
+tiletype0=0
+[INT_flor0003]
+Name=flor0003
+width=1
+height=1
+tiletype0=0
+[INT_flor0004]
+Name=flor0004
+width=1
+height=1
+tiletype0=0
+[INT_flor0005]
+Name=flor0005
+width=1
+height=1
+tiletype0=0
+[INT_flor0006]
+Name=flor0006
+width=1
+height=1
+tiletype0=0
+[INT_flor0007]
+Name=flor0007
+width=1
+height=1
+tiletype0=0
+
+[INT_gflr0001]
+Name=gflr0001
+width=1
+height=1
+tiletype0=0
+[INT_gflr0002]
+Name=gflr0002
+width=1
+height=1
+tiletype0=0
+[INT_gflr0003]
+Name=gflr0003
+width=1
+height=1
+tiletype0=0
+[INT_gflr0004]
+Name=gflr0004
+width=1
+height=1
+tiletype0=0
+[INT_gflr0005]
+Name=gflr0005
+width=1
+height=1
+tiletype0=0
+
+[INT_gstr0001]
+Name=gstr0001
+width=1
+height=1
+tiletype0=0
+[INT_gstr0002]
+Name=gstr0002
+width=1
+height=1
+tiletype0=0
+[INT_gstr0003]
+Name=gstr0003
+width=1
+height=1
+tiletype0=0
+[INT_gstr0004]
+Name=gstr0004
+width=1
+height=1
+tiletype0=0
+[INT_gstr0005]
+Name=gstr0005
+width=1
+height=1
+tiletype0=0
+[INT_gstr0006]
+Name=gstr0006
+width=1
+height=1
+tiletype0=0
+[INT_gstr0007]
+Name=gstr0007
+width=1
+height=1
+tiletype0=0
+[INT_gstr0008]
+Name=gstr0008
+width=1
+height=1
+tiletype0=0
+[INT_gstr0009]
+Name=gstr0009
+width=1
+height=1
+tiletype0=0
+[INT_gstr0010]
+Name=gstr0010
+width=1
+height=1
+tiletype0=0
+[INT_gstr0011]
+Name=gstr0011
+width=1
+height=1
+tiletype0=0
+
+[INT_lwal0001]
+Name=lwal0001
+width=1
+height=1
+tiletype0=7
+[INT_lwal0002]
+Name=lwal0002
+width=1
+height=1
+tiletype0=7
+[INT_lwal0003]
+Name=lwal0003
+width=1
+height=1
+tiletype0=7
+[INT_lwal0004]
+Name=lwal0004
+width=1
+height=1
+tiletype0=7
+[INT_lwal0005]
+Name=lwal0005
+width=1
+height=1
+tiletype0=7
+[INT_lwal0006]
+Name=lwal0006
+width=1
+height=1
+tiletype0=7
+[INT_lwal0007]
+Name=lwal0007
+width=1
+height=1
+tiletype0=7
+[INT_lwal0008]
+Name=lwal0008
+width=1
+height=1
+tiletype0=7
+[INT_lwal0009]
+Name=lwal0009
+width=1
+height=1
+tiletype0=7
+[INT_lwal0010]
+Name=lwal0010
+width=1
+height=1
+tiletype0=7
+[INT_lwal0011]
+Name=lwal0011
+width=1
+height=1
+tiletype0=7
+[INT_lwal0012]
+Name=lwal0012
+width=1
+height=1
+tiletype0=7
+[INT_lwal0013]
+Name=lwal0013
+width=1
+height=1
+tiletype0=7
+[INT_lwal0014]
+Name=lwal0014
+width=1
+height=1
+tiletype0=7
+[INT_lwal0015]
+Name=lwal0015
+width=1
+height=1
+tiletype0=7
+[INT_lwal0016]
+Name=lwal0016
+width=1
+height=1
+tiletype0=7
+[INT_lwal0017]
+Name=lwal0017
+width=1
+height=1
+tiletype0=7
+[INT_lwal0018]
+Name=lwal0018
+width=1
+height=1
+tiletype0=7
+[INT_lwal0019]
+Name=lwal0019
+width=1
+height=1
+tiletype0=7
+[INT_lwal0020]
+Name=lwal0020
+width=1
+height=1
+tiletype0=7
+[INT_lwal0021]
+Name=lwal0021
+width=1
+height=1
+tiletype0=7
+[INT_lwal0022]
+Name=lwal0022
+width=1
+height=1
+tiletype0=7
+[INT_lwal0023]
+Name=lwal0023
+width=1
+height=1
+tiletype0=7
+[INT_lwal0024]
+Name=lwal0024
+width=1
+height=1
+tiletype0=7
+[INT_lwal0025]
+Name=lwal0025
+width=1
+height=1
+tiletype0=7
+[INT_lwal0026]
+Name=lwal0026
+width=1
+height=1
+tiletype0=7
+[INT_lwal0027]
+Name=lwal0027
+width=1
+height=1
+tiletype0=7
+
+[INT_strp0001]
+Name=strp0001
+width=1
+height=1
+tiletype0=0
+[INT_strp0002]
+Name=strp0002
+width=1
+height=1
+tiletype0=0
+[INT_strp0003]
+Name=strp0003
+width=1
+height=1
+tiletype0=0
+[INT_strp0004]
+Name=strp0004
+width=1
+height=1
+tiletype0=0
+[INT_strp0005]
+Name=strp0005
+width=1
+height=1
+tiletype0=0
+[INT_strp0006]
+Name=strp0006
+width=1
+height=1
+tiletype0=0
+[INT_strp0007]
+Name=strp0007
+width=1
+height=1
+tiletype0=0
+[INT_strp0008]
+Name=strp0008
+width=1
+height=1
+tiletype0=0
+[INT_strp0009]
+Name=strp0009
+width=1
+height=1
+tiletype0=0
+[INT_strp0010]
+Name=strp0010
+width=1
+height=1
+tiletype0=0
+[INT_strp0011]
+Name=strp0011
+width=1
+height=1
+tiletype0=0
+
+[INT_wall0001]
+Name=wall0001
+width=1
+height=1
+tiletype0=7
+[INT_wall0002]
+Name=wall0002
+width=1
+height=1
+tiletype0=7
+[INT_wall0003]
+Name=wall0003
+width=1
+height=1
+tiletype0=7
+[INT_wall0004]
+Name=wall0004
+width=1
+height=1
+tiletype0=7
+[INT_wall0005]
+Name=wall0005
+width=1
+height=1
+tiletype0=7
+[INT_wall0006]
+Name=wall0006
+width=1
+height=1
+tiletype0=7
+[INT_wall0007]
+Name=wall0007
+width=1
+height=1
+tiletype0=7
+[INT_wall0008]
+Name=wall0008
+width=1
+height=1
+tiletype0=7
+[INT_wall0009]
+Name=wall0009
+width=1
+height=1
+tiletype0=7
+[INT_wall0010]
+Name=wall0010
+width=1
+height=1
+tiletype0=7
+[INT_wall0011]
+Name=wall0011
+width=1
+height=1
+tiletype0=7
+[INT_wall0012]
+Name=wall0012
+width=1
+height=1
+tiletype0=7
+[INT_wall0013]
+Name=wall0013
+width=1
+height=1
+tiletype0=7
+[INT_wall0014]
+Name=wall0014
+width=1
+height=1
+tiletype0=7
+[INT_wall0015]
+Name=wall0015
+width=1
+height=1
+tiletype0=7
+[INT_wall0016]
+Name=wall0016
+width=1
+height=1
+tiletype0=7
+[INT_wall0017]
+Name=wall0017
+width=1
+height=1
+tiletype0=7
+[INT_wall0018]
+Name=wall0018
+width=1
+height=1
+tiletype0=7
+[INT_wall0019]
+Name=wall0019
+width=1
+height=1
+tiletype0=7
+[INT_wall0020]
+Name=wall0020
+width=1
+height=1
+tiletype0=7
+[INT_wall0021]
+Name=wall0021
+width=1
+height=1
+tiletype0=7
+[INT_wall0022]
+Name=wall0022
+width=1
+height=1
+tiletype0=7
+
+[INT_wall0023]
+Name=wall0023
+width=2
+height=2
+tiletype0=7
+tiletype1=7
+tiletype2=7
+[INT_wall0024]
+Name=wall0024
+width=2
+height=2
+tiletype0=7
+tiletype1=7
+tiletype2=7
+[INT_wall0025]
+Name=wall0025
+width=2
+height=2
+tiletype0=7
+tiletype1=7
+tiletype2=7
+[INT_wall0026]
+Name=wall0026
+width=2
+height=2
+tiletype0=7
+tiletype1=7
+tiletype2=7
+[INT_wall0027]
+Name=wall0027
+width=2
+height=2
+tiletype0=7
+tiletype1=7
+tiletype3=7
+[INT_wall0028]
+Name=wall0028
+width=2
+height=2
+tiletype0=7
+tiletype1=7
+tiletype3=7
+[INT_wall0029]
+Name=wall0029
+width=2
+height=2
+tiletype0=7
+tiletype1=7
+tiletype3=7
+[INT_wall0030]
+Name=wall0030
+width=2
+height=2
+tiletype0=7
+tiletype1=7
+tiletype3=7
+[INT_wall0031]
+Name=wall0031
+width=2
+height=2
+tiletype0=7
+tiletype2=7
+tiletype3=7
+[INT_wall0032]
+Name=wall0032
+width=2
+height=2
+tiletype0=7
+tiletype2=7
+tiletype3=7
+[INT_wall0033]
+Name=wall0033
+width=2
+height=2
+tiletype0=7
+tiletype2=7
+tiletype3=7
+[INT_wall0034]
+Name=wall0034
+width=2
+height=2
+tiletype0=7
+tiletype2=7
+tiletype3=7
+[INT_wall0035]
+Name=wall0035
+width=2
+height=2
+tiletype1=7
+tiletype2=7
+tiletype3=7
+[INT_wall0036]
+Name=wall0036
+width=2
+height=2
+tiletype1=7
+tiletype2=7
+tiletype3=7
+[INT_wall0037]
+Name=wall0037
+width=2
+height=2
+tiletype1=7
+tiletype2=7
+tiletype3=7
+[INT_wall0038]
+Name=wall0038
+width=2
+height=2
+tiletype1=7
+tiletype2=7
+tiletype3=7
+
+[INT_wall0039]
+Name=wall0039
+width=2
+height=3
+tiletype0=7
+tiletype2=7
+tiletype3=7
+tiletype4=7
+[INT_wall0040]
+Name=wall0040
+width=2
+height=3
+tiletype0=7
+tiletype2=7
+tiletype3=7
+tiletype4=7
+[INT_wall0041]
+Name=wall0041
+width=2
+height=3
+tiletype1=7
+tiletype2=7
+tiletype3=7
+tiletype5=7
+[INT_wall0042]
+Name=wall0042
+width=2
+height=3
+tiletype1=7
+tiletype2=7
+tiletype3=7
+tiletype5=7
+
+[INT_wall0043]
+Name=wall0043
+width=3
+height=2
+tiletype1=7
+tiletype3=7
+tiletype4=7
+tiletype5=7
+[INT_wall0044]
+Name=wall0044
+width=3
+height=2
+tiletype1=7
+tiletype3=7
+tiletype4=7
+tiletype5=7
+[INT_wall0045]
+Name=wall0045
+width=3
+height=2
+tiletype1=7
+tiletype3=7
+tiletype4=7
+tiletype5=7
+[INT_wall0046]
+Name=wall0046
+width=3
+height=2
+tiletype1=7
+tiletype3=7
+tiletype4=7
+tiletype5=7
+[INT_wall0047]
+Name=wall0047
+width=3
+height=2
+tiletype0=7
+tiletype1=7
+tiletype2=7
+tiletype4=7
+[INT_wall0048]
+Name=wall0048
+width=3
+height=2
+tiletype0=7
+tiletype1=7
+tiletype2=7
+tiletype4=7
+[INT_wall0049]
+Name=wall0049
+width=3
+height=3
+tiletype1=7
+tiletype3=7
+tiletype4=7
+tiletype5=7
+tiletype7=7
+
+[INT_xtra0001]
+Name=xtra0001
+width=1
+height=1
+tiletype0=7
+[INT_xtra0002]
+Name=xtra0002
+width=2
+height=1
+tiletype0=7
+tiletype1=0
+[INT_xtra0003]
+Name=xtra0003
+width=1
+height=1
+tiletype0=7
+[INT_xtra0004]
+Name=xtra0004
+width=1
+height=2
+tiletype0=7
+tiletype1=0
+[INT_xtra0005]
+Name=xtra0005
+width=1
+height=1
+tiletype0=7
+[INT_xtra0006]
+Name=xtra0006
+width=2
+height=1
+tiletype0=7
+tiletype1=0
+[INT_xtra0007]
+Name=xtra0007
+width=1
+height=1
+tiletype0=7
+[INT_xtra0008]
+Name=xtra0008
+width=1
+height=2
+tiletype0=7
+tiletype1=0
+[INT_xtra0009]
+Name=xtra0009
+width=1
+height=1
+tiletype0=7
+[INT_xtra0010]
+Name=xtra0010
+width=1
+height=1
+tiletype0=7
+[INT_xtra0011]
+Name=xtra0011
+width=1
+height=1
+tiletype0=7
+[INT_xtra0012]
+Name=xtra0012
+width=1
+height=2
+tiletype0=7
+tiletype1=0
+[INT_xtra0013]
+Name=xtra0013
+width=1
+height=2
+tiletype0=7
+tiletype1=0
+[INT_xtra0014]
+Name=xtra0014
+width=3
+height=2
+tiletype0=0
+tiletype1=7
+tiletype2=0
+tiletype3=0
+tiletype4=0
+tiletype5=0
+[INT_xtra0015]
+Name=xtra0015
+width=3
+height=2
+tiletype0=7
+tiletype1=7
+tiletype2=7
+tiletype3=7
+tiletype4=7
+tiletype5=7
+[INT_xtra0016]
+Name=xtra0016
+width=2
+height=4
+tiletype0=7
+tiletype1=7
+tiletype2=7
+tiletype3=7
+tiletype4=7
+tiletype5=7
+tiletype6=7
+tiletype7=7
+
+; special tile
 [TEM65534]
 Name=Bogus
 width=1
 height=1
-tiletype0=10
\ No newline at end of file
+tiletype0=10