diff --git a/OpenRA.Game/Exts.cs b/OpenRA.Game/Exts.cs
index 11a428e089..53de85d9c7 100644
--- a/OpenRA.Game/Exts.cs
+++ b/OpenRA.Game/Exts.cs
@@ -361,7 +361,7 @@ namespace OpenRA
 
 		public static Dictionary<TKey, TElement> ToDictionaryWithConflictLog<TSource, TKey, TElement>(
 			this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, Func<TSource, TElement> elementSelector,
-			string debugName, Func<TKey, string> logKey, Func<TElement, string> logValue)
+			string debugName, Func<TKey, string> logKey = null, Func<TElement, string> logValue = null)
 		{
 			// Fall back on ToString() if null functions are provided:
 			logKey = logKey ?? (s => s.ToString());
diff --git a/OpenRA.Game/GameRules/Ruleset.cs b/OpenRA.Game/GameRules/Ruleset.cs
index 01a2e5fa93..0f7e299076 100644
--- a/OpenRA.Game/GameRules/Ruleset.cs
+++ b/OpenRA.Game/GameRules/Ruleset.cs
@@ -9,8 +9,11 @@
  */
 #endregion
 
+using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Threading.Tasks;
+using OpenRA.FileSystem;
 using OpenRA.GameRules;
 using OpenRA.Graphics;
 using OpenRA.Traits;
@@ -24,25 +27,25 @@ namespace OpenRA
 		public readonly IReadOnlyDictionary<string, SoundInfo> Voices;
 		public readonly IReadOnlyDictionary<string, SoundInfo> Notifications;
 		public readonly IReadOnlyDictionary<string, MusicInfo> Music;
-		public readonly IReadOnlyDictionary<string, TileSet> TileSets;
-		public readonly IReadOnlyDictionary<string, SequenceProvider> Sequences;
+		public readonly TileSet TileSet;
+		public readonly SequenceProvider Sequences;
 
 		public Ruleset(
-			IDictionary<string, ActorInfo> actors,
-			IDictionary<string, WeaponInfo> weapons,
-			IDictionary<string, SoundInfo> voices,
-			IDictionary<string, SoundInfo> notifications,
-			IDictionary<string, MusicInfo> music,
-			IDictionary<string, TileSet> tileSets,
-			IDictionary<string, SequenceProvider> sequences)
+			IReadOnlyDictionary<string, ActorInfo> actors,
+			IReadOnlyDictionary<string, WeaponInfo> weapons,
+			IReadOnlyDictionary<string, SoundInfo> voices,
+			IReadOnlyDictionary<string, SoundInfo> notifications,
+			IReadOnlyDictionary<string, MusicInfo> music,
+			TileSet tileSet,
+			SequenceProvider sequences)
 		{
-			Actors = new ReadOnlyDictionary<string, ActorInfo>(actors);
-			Weapons = new ReadOnlyDictionary<string, WeaponInfo>(weapons);
-			Voices = new ReadOnlyDictionary<string, SoundInfo>(voices);
-			Notifications = new ReadOnlyDictionary<string, SoundInfo>(notifications);
-			Music = new ReadOnlyDictionary<string, MusicInfo>(music);
-			TileSets = new ReadOnlyDictionary<string, TileSet>(tileSets);
-			Sequences = new ReadOnlyDictionary<string, SequenceProvider>(sequences);
+			Actors = actors;
+			Weapons = weapons;
+			Voices = voices;
+			Notifications = notifications;
+			Music = music;
+			TileSet = tileSet;
+			Sequences = sequences;
 
 			foreach (var a in Actors.Values)
 			{
@@ -80,5 +83,120 @@ namespace OpenRA
 		}
 
 		public IEnumerable<KeyValuePair<string, MusicInfo>> InstalledMusic { get { return Music.Where(m => m.Value.Exists); } }
+
+		static IReadOnlyDictionary<string, T> MergeOrDefault<T>(string name, IReadOnlyFileSystem fileSystem, IEnumerable<string> files, MiniYaml additional,
+			IReadOnlyDictionary<string, T> defaults, Func<MiniYamlNode, T> makeObject)
+		{
+			if (additional == null && defaults != null)
+				return defaults;
+
+			var result = MiniYaml.Load(fileSystem, files, additional)
+				.ToDictionaryWithConflictLog(k => k.Key.ToLowerInvariant(), makeObject, "LoadFromManifest<" + name + ">");
+
+			return new ReadOnlyDictionary<string, T>(result);
+		}
+
+		public static Ruleset LoadDefaults(ModData modData)
+		{
+			var m = modData.Manifest;
+			var fs = modData.DefaultFileSystem;
+
+			Ruleset ruleset = null;
+			Action f = () =>
+			{
+				var actors = MergeOrDefault("Manifest,Rules", fs, m.Rules, null, null,
+					k => new ActorInfo(modData.ObjectCreator, k.Key.ToLowerInvariant(), k.Value));
+
+				var weapons = MergeOrDefault("Manifest,Weapons", fs, m.Weapons, null, null,
+					k => new WeaponInfo(k.Key.ToLowerInvariant(), k.Value));
+
+				var voices = MergeOrDefault("Manifest,Voices", fs, m.Voices, null, null,
+					k => new SoundInfo(k.Value));
+
+				var notifications = MergeOrDefault("Manifest,Notifications", fs, m.Notifications, null, null,
+					k => new SoundInfo(k.Value));
+
+				var music = MergeOrDefault("Manifest,Music", fs, m.Music, null, null,
+					k => new MusicInfo(k.Key, k.Value));
+
+				// The default ruleset does not include a preferred tileset or sequence set
+				ruleset = new Ruleset(actors, weapons, voices, notifications, music, null, null);
+			};
+
+			if (modData.IsOnMainThread)
+			{
+				modData.HandleLoadingProgress();
+
+				var loader = new Task(f);
+				loader.Start();
+
+				// Animate the loadscreen while we wait
+				while (!loader.Wait(40))
+					modData.HandleLoadingProgress();
+			}
+			else
+				f();
+
+			return ruleset;
+		}
+
+		public static Ruleset LoadDefaultsForTileSet(ModData modData, string tileSet)
+		{
+			var dr = modData.DefaultRules;
+			var ts = modData.DefaultTileSets[tileSet];
+			var sequences = modData.DefaultSequences[tileSet];
+			return new Ruleset(dr.Actors, dr.Weapons, dr.Voices, dr.Notifications, dr.Music, ts, sequences);
+		}
+
+		public static Ruleset LoadFromMap(ModData modData, Map map)
+		{
+			var m = modData.Manifest;
+			var dr = modData.DefaultRules;
+
+			Ruleset ruleset = null;
+			Action f = () =>
+			{
+				var actors = MergeOrDefault("Manifest,Rules", map, m.Rules, map.RuleDefinitions, dr.Actors,
+					k => new ActorInfo(modData.ObjectCreator, k.Key.ToLowerInvariant(), k.Value));
+
+				var weapons = MergeOrDefault("Manifest,Weapons", map, m.Weapons, map.WeaponDefinitions, dr.Weapons,
+					k => new WeaponInfo(k.Key.ToLowerInvariant(), k.Value));
+
+				var voices = MergeOrDefault("Manifest,Voices", map, m.Voices, map.VoiceDefinitions, dr.Voices,
+					k => new SoundInfo(k.Value));
+
+				var notifications = MergeOrDefault("Manifest,Notifications", map, m.Notifications, map.NotificationDefinitions, dr.Notifications,
+					k => new SoundInfo(k.Value));
+
+				var music = MergeOrDefault("Manifest,Music", map, m.Music, map.NotificationDefinitions, dr.Music,
+					k => new MusicInfo(k.Key, k.Value));
+
+				// TODO: Add support for merging custom tileset modifications
+				var ts = modData.DefaultTileSets[map.Tileset];
+
+				// TODO: Top-level dictionary should be moved into the Ruleset instead of in its own object
+				var sequences = map.SequenceDefinitions == null ? modData.DefaultSequences[map.Tileset] :
+					new SequenceProvider(map, modData, ts, map.SequenceDefinitions);
+
+				// TODO: Add support for custom voxel sequences
+				ruleset = new Ruleset(actors, weapons, voices, notifications, music, ts, sequences);
+			};
+
+			if (modData.IsOnMainThread)
+			{
+				modData.HandleLoadingProgress();
+
+				var loader = new Task(f);
+				loader.Start();
+
+				// Animate the loadscreen while we wait
+				while (!loader.Wait(40))
+					modData.HandleLoadingProgress();
+			}
+			else
+				f();
+
+			return ruleset;
+		}
 	}
 }
diff --git a/OpenRA.Game/GameRules/RulesetCache.cs b/OpenRA.Game/GameRules/RulesetCache.cs
deleted file mode 100644
index b308b18a8e..0000000000
--- a/OpenRA.Game/GameRules/RulesetCache.cs
+++ /dev/null
@@ -1,159 +0,0 @@
-#region Copyright & License Information
-/*
- * Copyright 2007-2016 The OpenRA Developers (see AUTHORS)
- * This file is part of OpenRA, which is free software. It is made
- * available to you under the terms of the GNU General Public License
- * as published by the Free Software Foundation, either version 3 of
- * the License, or (at your option) any later version. For more
- * information, see COPYING.
- */
-#endregion
-
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using OpenRA.FileSystem;
-using OpenRA.GameRules;
-using OpenRA.Graphics;
-using OpenRA.Support;
-
-namespace OpenRA
-{
-	public sealed class RulesetCache
-	{
-		readonly ModData modData;
-
-		readonly Dictionary<string, ActorInfo> actorCache = new Dictionary<string, ActorInfo>();
-		readonly Dictionary<string, WeaponInfo> weaponCache = new Dictionary<string, WeaponInfo>();
-		readonly Dictionary<string, SoundInfo> voiceCache = new Dictionary<string, SoundInfo>();
-		readonly Dictionary<string, SoundInfo> notificationCache = new Dictionary<string, SoundInfo>();
-		readonly Dictionary<string, MusicInfo> musicCache = new Dictionary<string, MusicInfo>();
-		readonly Dictionary<string, TileSet> tileSetCache = new Dictionary<string, TileSet>();
-
-		public event EventHandler LoadingProgress;
-		void RaiseProgress()
-		{
-			if (LoadingProgress != null)
-				LoadingProgress(this, new EventArgs());
-		}
-
-		public RulesetCache(ModData modData)
-		{
-			this.modData = modData;
-		}
-
-		public Ruleset Load(IReadOnlyFileSystem fileSystem,
-			MiniYaml additionalRules,
-			MiniYaml additionalWeapons,
-			MiniYaml additionalVoices,
-			MiniYaml additionalNotifications,
-			MiniYaml additionalMusic,
-			MiniYaml additionalSequences)
-		{
-			var m = modData.Manifest;
-
-			Dictionary<string, ActorInfo> actors;
-			Dictionary<string, WeaponInfo> weapons;
-			Dictionary<string, SoundInfo> voices;
-			Dictionary<string, SoundInfo> notifications;
-			Dictionary<string, MusicInfo> music;
-			Dictionary<string, TileSet> tileSets;
-
-			using (new PerfTimer("Actors"))
-				actors = LoadYamlRules(fileSystem, actorCache, m.Rules, additionalRules,
-					k => new ActorInfo(Game.ModData.ObjectCreator, k.Key.ToLowerInvariant(), k.Value));
-
-			using (new PerfTimer("Weapons"))
-				weapons = LoadYamlRules(fileSystem, weaponCache, m.Weapons, additionalWeapons,
-					k => new WeaponInfo(k.Key.ToLowerInvariant(), k.Value));
-
-			using (new PerfTimer("Voices"))
-				voices = LoadYamlRules(fileSystem, voiceCache, m.Voices, additionalVoices,
-					k => new SoundInfo(k.Value));
-
-			using (new PerfTimer("Notifications"))
-				notifications = LoadYamlRules(fileSystem, notificationCache, m.Notifications, additionalNotifications,
-					k => new SoundInfo(k.Value));
-
-			using (new PerfTimer("Music"))
-				music = LoadYamlRules(fileSystem, musicCache, m.Music, additionalMusic,
-					k => new MusicInfo(k.Key, k.Value));
-
-			using (new PerfTimer("TileSets"))
-				tileSets = LoadTileSets(fileSystem, tileSetCache, m.TileSets);
-
-			// TODO: only initialize, and then cache, the provider for the given map
-			var sequences = tileSets.ToDictionary(t => t.Key, t => new SequenceProvider(fileSystem, modData, t.Value, additionalSequences));
-			return new Ruleset(actors, weapons, voices, notifications, music, tileSets, sequences);
-		}
-
-		/// <summary>
-		/// Cache and return the Ruleset for a given map.
-		/// If a map isn't specified then return the default mod Ruleset.
-		/// </summary>
-		public Ruleset Load(IReadOnlyFileSystem fileSystem, Map map = null)
-		{
-			return map != null ? Load(fileSystem, map.RuleDefinitions, map.WeaponDefinitions,
-				map.VoiceDefinitions, map.NotificationDefinitions, map.MusicDefinitions,
-				map.SequenceDefinitions) : Load(fileSystem, null, null, null, null, null, null);
-		}
-
-		Dictionary<string, T> LoadYamlRules<T>(IReadOnlyFileSystem fileSystem,
-			Dictionary<string, T> itemCache,
-			IEnumerable<string> files, MiniYaml mapRules,
-			Func<MiniYamlNode, T> f)
-		{
-			RaiseProgress();
-
-			if (mapRules != null && mapRules.Value != null)
-				files = files.Append(FieldLoader.GetValue<string[]>("value", mapRules.Value));
-
-			var inputKey = string.Join("|", files);
-			if (mapRules != null && mapRules.Nodes.Any())
-				inputKey += "|" + mapRules.Nodes.WriteToString();
-
-			Func<MiniYamlNode, T> wrap = wkv =>
-			{
-				var key = inputKey + wkv.Value.ToLines(wkv.Key).JoinWith("|");
-				T t;
-				if (itemCache.TryGetValue(key, out t))
-					return t;
-
-				t = f(wkv);
-				itemCache.Add(key, t);
-
-				RaiseProgress();
-				return t;
-			};
-
-			var tree = MiniYaml.Load(fileSystem, files, mapRules).ToDictionaryWithConflictLog(
-				n => n.Key, n => n.Value, "LoadYamlRules", null, null);
-
-			RaiseProgress();
-
-			var itemSet = tree.ToDictionary(kv => kv.Key.ToLowerInvariant(), kv => wrap(new MiniYamlNode(kv.Key, kv.Value)));
-			RaiseProgress();
-			return itemSet;
-		}
-
-		Dictionary<string, TileSet> LoadTileSets(IReadOnlyFileSystem fileSystem, Dictionary<string, TileSet> itemCache, string[] files)
-		{
-			var items = new Dictionary<string, TileSet>();
-
-			foreach (var file in files)
-			{
-				TileSet t;
-				if (itemCache.TryGetValue(file, out t))
-					items.Add(t.Id, t);
-				else
-				{
-					t = new TileSet(fileSystem, file);
-					itemCache.Add(file, t);
-					items.Add(t.Id, t);
-				}
-			}
-
-			return items;
-		}
-	}
-}
diff --git a/OpenRA.Game/Map/Map.cs b/OpenRA.Game/Map/Map.cs
index a674b4c212..6fd195351e 100644
--- a/OpenRA.Game/Map/Map.cs
+++ b/OpenRA.Game/Map/Map.cs
@@ -169,10 +169,9 @@ namespace OpenRA
 		[FieldLoader.Ignore] CellLayer<PPos[]> cellProjection;
 		[FieldLoader.Ignore] CellLayer<List<MPos>> inverseCellProjection;
 
-		[FieldLoader.Ignore] Lazy<TileSet> cachedTileSet;
 		[FieldLoader.Ignore] Lazy<Ruleset> rules;
 		public Ruleset Rules { get { return rules != null ? rules.Value : null; } }
-		public SequenceProvider SequenceProvider { get { return Rules.Sequences[Tileset]; } }
+		public SequenceProvider SequenceProvider { get { return Rules.Sequences; } }
 
 		[FieldLoader.Ignore] public ProjectedCellRegion ProjectedCellBounds;
 		[FieldLoader.Ignore] public CellRegion AllCells;
@@ -297,7 +296,7 @@ namespace OpenRA
 			{
 				try
 				{
-					return modData.RulesetCache.Load(this, this);
+					return Ruleset.LoadFromMap(modData, this);
 				}
 				catch (Exception e)
 				{
@@ -305,11 +304,9 @@ namespace OpenRA
 					Log.Write("debug", "Failed to load rules for {0} with error {1}", Title, e.Message);
 				}
 
-				return modData.DefaultRules;
+				return Ruleset.LoadDefaultsForTileSet(modData, Tileset);
 			});
 
-			cachedTileSet = Exts.Lazy(() => Rules.TileSets[Tileset]);
-
 			var tl = new MPos(0, 0).ToCPos(this);
 			var br = new MPos(MapSize.X - 1, MapSize.Y - 1).ToCPos(this);
 			AllCells = new CellRegion(Grid.Type, tl, br);
@@ -391,7 +388,7 @@ namespace OpenRA
 			// Odd-height ramps get bumped up a level to the next even height layer
 			if ((height & 1) == 1)
 			{
-				var ti = cachedTileSet.Value.GetTileInfo(MapTiles.Value[uv]);
+				var ti = Rules.TileSet.GetTileInfo(MapTiles.Value[uv]);
 				if (ti != null && ti.RampType != 0)
 					height += 1;
 			}
@@ -627,7 +624,7 @@ namespace OpenRA
 
 		public byte[] SavePreview()
 		{
-			var tileset = Rules.TileSets[Tileset];
+			var tileset = Rules.TileSet;
 			var resources = Rules.Actors["world"].TraitInfos<ResourceTypeInfo>()
 				.ToDictionary(r => r.ResourceType, r => r.TerrainType);
 
@@ -878,7 +875,7 @@ namespace OpenRA
 		public void FixOpenAreas()
 		{
 			var r = new Random();
-			var tileset = Rules.TileSets[Tileset];
+			var tileset = Rules.TileSet;
 
 			for (var j = Bounds.Top; j < Bounds.Bottom; j++)
 			{
@@ -926,7 +923,7 @@ namespace OpenRA
 			{
 				var custom = CustomTerrain[uv];
 				terrainIndex = cachedTerrainIndexes[uv] =
-					custom != byte.MaxValue ? custom : cachedTileSet.Value.GetTerrainIndex(MapTiles.Value[uv]);
+					custom != byte.MaxValue ? custom : Rules.TileSet.GetTerrainIndex(MapTiles.Value[uv]);
 			}
 
 			return (byte)terrainIndex;
@@ -934,7 +931,7 @@ namespace OpenRA
 
 		public TerrainTypeInfo GetTerrainInfo(CPos cell)
 		{
-			return cachedTileSet.Value[GetTerrainIndex(cell)];
+			return Rules.TileSet[GetTerrainIndex(cell)];
 		}
 
 		public CPos Clamp(CPos cell)
diff --git a/OpenRA.Game/ModData.cs b/OpenRA.Game/ModData.cs
index b20b31e25c..1792eaa620 100644
--- a/OpenRA.Game/ModData.cs
+++ b/OpenRA.Game/ModData.cs
@@ -30,15 +30,20 @@ namespace OpenRA
 		public readonly ISoundLoader[] SoundLoaders;
 		public readonly ISpriteLoader[] SpriteLoaders;
 		public readonly ISpriteSequenceLoader SpriteSequenceLoader;
-		public readonly RulesetCache RulesetCache;
 		public ILoadScreen LoadScreen { get; private set; }
 		public VoxelLoader VoxelLoader { get; private set; }
 		public CursorProvider CursorProvider { get; private set; }
 		public FS ModFiles = new FS();
+		public IReadOnlyFileSystem DefaultFileSystem { get { return ModFiles; } }
 
 		readonly Lazy<Ruleset> defaultRules;
 		public Ruleset DefaultRules { get { return defaultRules.Value; } }
-		public IReadOnlyFileSystem DefaultFileSystem { get { return ModFiles; } }
+
+		readonly Lazy<IReadOnlyDictionary<string, TileSet>> defaultTileSets;
+		public IReadOnlyDictionary<string, TileSet> DefaultTileSets { get { return defaultTileSets.Value; } }
+
+		readonly Lazy<IReadOnlyDictionary<string, SequenceProvider>> defaultSequences;
+		public IReadOnlyDictionary<string, SequenceProvider> DefaultSequences { get { return defaultSequences.Value; } }
 
 		public ModData(string mod, bool useLoadScreen = false)
 		{
@@ -57,8 +62,6 @@ namespace OpenRA
 			}
 
 			WidgetLoader = new WidgetLoader(this);
-			RulesetCache = new RulesetCache(this);
-			RulesetCache.LoadingProgress += HandleLoadingProgress;
 			MapCache = new MapCache(this);
 
 			SoundLoaders = GetLoaders<ISoundLoader>(Manifest.SoundFormats, "sound");
@@ -73,19 +76,39 @@ namespace OpenRA
 			SpriteSequenceLoader = (ISpriteSequenceLoader)ctor.Invoke(new[] { this });
 			SpriteSequenceLoader.OnMissingSpriteError = s => Log.Write("debug", s);
 
-			defaultRules = Exts.Lazy(() => RulesetCache.Load(DefaultFileSystem));
+			defaultRules = Exts.Lazy(() => Ruleset.LoadDefaults(this));
+			defaultTileSets = Exts.Lazy(() =>
+			{
+				var items = new Dictionary<string, TileSet>();
+
+				foreach (var file in Manifest.TileSets)
+				{
+					var t = new TileSet(DefaultFileSystem, file);
+					items.Add(t.Id, t);
+				}
+
+				return (IReadOnlyDictionary<string, TileSet>)(new ReadOnlyDictionary<string, TileSet>(items));
+			});
+
+			defaultSequences = Exts.Lazy(() =>
+			{
+				var items = DefaultTileSets.ToDictionary(t => t.Key, t => new SequenceProvider(DefaultFileSystem, this, t.Value, null));
+				return (IReadOnlyDictionary<string, SequenceProvider>)(new ReadOnlyDictionary<string, SequenceProvider>(items));
+			});
 
 			initialThreadId = System.Threading.Thread.CurrentThread.ManagedThreadId;
 		}
 
 		// HACK: Only update the loading screen if we're in the main thread.
 		int initialThreadId;
-		void HandleLoadingProgress(object sender, EventArgs e)
+		internal void HandleLoadingProgress()
 		{
-			if (LoadScreen != null && System.Threading.Thread.CurrentThread.ManagedThreadId == initialThreadId)
+			if (LoadScreen != null && IsOnMainThread)
 				LoadScreen.Display();
 		}
 
+		internal bool IsOnMainThread { get { return System.Threading.Thread.CurrentThread.ManagedThreadId == initialThreadId; } }
+
 		public void InitializeLoaders(IReadOnlyFileSystem fileSystem)
 		{
 			// all this manipulation of static crap here is nasty and breaks
diff --git a/OpenRA.Game/OpenRA.Game.csproj b/OpenRA.Game/OpenRA.Game.csproj
index 983eeceb19..d75b30c3ee 100644
--- a/OpenRA.Game/OpenRA.Game.csproj
+++ b/OpenRA.Game/OpenRA.Game.csproj
@@ -215,7 +215,6 @@
     <Compile Include="Primitives\ReadOnlyList.cs" />
     <Compile Include="ModMetadata.cs" />
     <Compile Include="GameRules\Ruleset.cs" />
-    <Compile Include="GameRules\RulesetCache.cs" />
     <Compile Include="Support\MersenneTwister.cs" />
     <Compile Include="GameInformation.cs" />
     <Compile Include="Map\CellLayer.cs" />
diff --git a/OpenRA.Game/World.cs b/OpenRA.Game/World.cs
index 98bffa816a..23ef101885 100644
--- a/OpenRA.Game/World.cs
+++ b/OpenRA.Game/World.cs
@@ -160,7 +160,7 @@ namespace OpenRA
 			Map = map;
 			Timestep = orderManager.LobbyInfo.GlobalSettings.Timestep;
 
-			TileSet = map.Rules.TileSets[Map.Tileset];
+			TileSet = map.Rules.TileSet;
 			SharedRandom = new MersenneTwister(orderManager.LobbyInfo.GlobalSettings.RandomSeed);
 
 			var worldActorType = type == WorldType.Editor ? "EditorWorld" : "World";
diff --git a/OpenRA.Mods.Common/EditorBrushes/EditorResourceBrush.cs b/OpenRA.Mods.Common/EditorBrushes/EditorResourceBrush.cs
index 47fdd2b85c..85f9a92f72 100644
--- a/OpenRA.Mods.Common/EditorBrushes/EditorResourceBrush.cs
+++ b/OpenRA.Mods.Common/EditorBrushes/EditorResourceBrush.cs
@@ -37,7 +37,7 @@ namespace OpenRA.Mods.Common.Widgets
 			preview.IsVisible = () => editorWidget.CurrentBrush == this;
 
 			var variant = resource.Variants.FirstOrDefault();
-			var sequenceProvider = wr.World.Map.Rules.Sequences[world.TileSet.Id];
+			var sequenceProvider = wr.World.Map.Rules.Sequences;
 			var sequence = sequenceProvider.GetSequence("resources", variant);
 			var sprite = sequence.GetSprite(resource.MaxDensity - 1);
 			preview.GetSprite = () => sprite;
diff --git a/OpenRA.Mods.Common/EditorBrushes/EditorTileBrush.cs b/OpenRA.Mods.Common/EditorBrushes/EditorTileBrush.cs
index 1f1796d231..5c2ab6f272 100644
--- a/OpenRA.Mods.Common/EditorBrushes/EditorTileBrush.cs
+++ b/OpenRA.Mods.Common/EditorBrushes/EditorTileBrush.cs
@@ -100,8 +100,7 @@ namespace OpenRA.Mods.Common.Widgets
 			var mapTiles = map.MapTiles.Value;
 			var mapHeight = map.MapHeight.Value;
 
-			var rules = map.Rules;
-			var tileset = rules.TileSets[map.Tileset];
+			var tileset = map.Rules.TileSet;
 			var template = tileset.Templates[Template];
 			var baseHeight = mapHeight.Contains(cell) ? mapHeight[cell] : (byte)0;
 
@@ -139,8 +138,7 @@ namespace OpenRA.Mods.Common.Widgets
 			var queue = new Queue<CPos>();
 			var touched = new CellLayer<bool>(map);
 
-			var rules = map.Rules;
-			var tileset = rules.TileSets[map.Tileset];
+			var tileset = map.Rules.TileSet;
 			var template = tileset.Templates[Template];
 
 			Action<CPos> maybeEnqueue = newCell =>
diff --git a/OpenRA.Mods.Common/Lint/CheckSequences.cs b/OpenRA.Mods.Common/Lint/CheckSequences.cs
index d1ed7d0e72..166d25c1e9 100644
--- a/OpenRA.Mods.Common/Lint/CheckSequences.cs
+++ b/OpenRA.Mods.Common/Lint/CheckSequences.cs
@@ -36,7 +36,7 @@ namespace OpenRA.Mods.Common.Lint
 
 			var rules = map.Rules;
 			var factions = rules.Actors["world"].TraitInfos<FactionInfo>().Select(f => f.InternalName).ToArray();
-			var sequenceProviders = new[] { rules.Sequences[map.Tileset] };
+			var sequenceProviders = new[] { rules.Sequences };
 
 			foreach (var actorInfo in rules.Actors)
 			{
diff --git a/OpenRA.Mods.Common/ServerTraits/LobbyCommands.cs b/OpenRA.Mods.Common/ServerTraits/LobbyCommands.cs
index 0285393c24..39ac629eb5 100644
--- a/OpenRA.Mods.Common/ServerTraits/LobbyCommands.cs
+++ b/OpenRA.Mods.Common/ServerTraits/LobbyCommands.cs
@@ -308,7 +308,7 @@ namespace OpenRA.Mods.Common.Server
 
 							// Pick a random color for the bot
 							var validator = server.ModData.Manifest.Get<ColorValidator>();
-							var tileset = server.Map.Rules.TileSets[server.Map.Tileset];
+							var tileset = server.Map.Rules.TileSet;
 							var terrainColors = tileset.TerrainInfo.Where(ti => ti.RestrictPlayerColor).Select(ti => ti.Color);
 							var playerColors = server.LobbyInfo.Clients.Select(c => c.Color.RGB)
 								.Concat(server.MapPlayers.Players.Values.Select(p => p.Color.RGB));
@@ -1064,7 +1064,7 @@ namespace OpenRA.Mods.Common.Server
 					server.SendOrderTo(connectionToEcho, "Message", message);
 			};
 
-			var tileset = server.Map.Rules.TileSets[server.Map.Tileset];
+			var tileset = server.Map.Rules.TileSet;
 			var terrainColors = tileset.TerrainInfo.Where(ti => ti.RestrictPlayerColor).Select(ti => ti.Color).ToList();
 			var playerColors = server.LobbyInfo.Clients.Where(c => c.Index != playerIndex).Select(c => c.Color.RGB)
 				.Concat(server.MapPlayers.Players.Values.Select(p => p.Color.RGB)).ToList();
diff --git a/OpenRA.Mods.Common/UtilityCommands/CheckYaml.cs b/OpenRA.Mods.Common/UtilityCommands/CheckYaml.cs
index 943fb2edb2..ee47648cdb 100644
--- a/OpenRA.Mods.Common/UtilityCommands/CheckYaml.cs
+++ b/OpenRA.Mods.Common/UtilityCommands/CheckYaml.cs
@@ -127,7 +127,6 @@ namespace OpenRA.Mods.Common.UtilityCommands
 			{
 				try
 				{
-					modData.RulesetCache.Load(map ?? modData.DefaultFileSystem, map);
 					var customRulesPass = (ILintRulesPass)modData.ObjectCreator.CreateBasic(customRulesPassType);
 					customRulesPass.Run(EmitError, EmitWarning, rules);
 				}
diff --git a/OpenRA.Mods.Common/UtilityCommands/ExtractLanguageStringsCommand.cs b/OpenRA.Mods.Common/UtilityCommands/ExtractLanguageStringsCommand.cs
index 0534c7d6ba..712143d64b 100644
--- a/OpenRA.Mods.Common/UtilityCommands/ExtractLanguageStringsCommand.cs
+++ b/OpenRA.Mods.Common/UtilityCommands/ExtractLanguageStringsCommand.cs
@@ -30,7 +30,6 @@ namespace OpenRA.Mods.Common.UtilityCommands
 		{
 			// HACK: The engine code assumes that Game.modData is set.
 			Game.ModData = modData;
-			modData.RulesetCache.Load(modData.DefaultFileSystem);
 
 			var types = Game.ModData.ObjectCreator.GetTypes();
 			var translatableFields = types.SelectMany(t => t.GetFields())
diff --git a/OpenRA.Mods.Common/UtilityCommands/ImportLegacyMapCommand.cs b/OpenRA.Mods.Common/UtilityCommands/ImportLegacyMapCommand.cs
index 28ee6125a2..2728cddcef 100644
--- a/OpenRA.Mods.Common/UtilityCommands/ImportLegacyMapCommand.cs
+++ b/OpenRA.Mods.Common/UtilityCommands/ImportLegacyMapCommand.cs
@@ -60,7 +60,7 @@ namespace OpenRA.Mods.Common.UtilityCommands
 				ValidateMapFormat(format);
 
 				var tileset = GetTileset(mapSection);
-				Map = new Map(modData, modData.DefaultRules.TileSets[tileset], MapSize, MapSize)
+				Map = new Map(modData, modData.DefaultTileSets[tileset], MapSize, MapSize)
 				{
 					Title = basic.GetValue("Name", Path.GetFileNameWithoutExtension(filename)),
 					Author = "Westwood Studios",
diff --git a/OpenRA.Mods.Common/UtilityCommands/RemapShpCommand.cs b/OpenRA.Mods.Common/UtilityCommands/RemapShpCommand.cs
index f18f0bc33d..9b892dc179 100644
--- a/OpenRA.Mods.Common/UtilityCommands/RemapShpCommand.cs
+++ b/OpenRA.Mods.Common/UtilityCommands/RemapShpCommand.cs
@@ -42,15 +42,13 @@ namespace OpenRA.Mods.Common.UtilityCommands
 			var srcModData = new ModData(srcMod);
 			Game.ModData = srcModData;
 
-			var srcRules = srcModData.RulesetCache.Load(srcModData.DefaultFileSystem);
-			var srcPaletteInfo = srcRules.Actors["player"].TraitInfo<PlayerColorPaletteInfo>();
+			var srcPaletteInfo = srcModData.DefaultRules.Actors["player"].TraitInfo<PlayerColorPaletteInfo>();
 			var srcRemapIndex = srcPaletteInfo.RemapIndex;
 
 			var destMod = args[2].Split(':')[0];
 			var destModData = new ModData(destMod);
 			Game.ModData = destModData;
-			var destRules = destModData.RulesetCache.Load(destModData.DefaultFileSystem);
-			var destPaletteInfo = destRules.Actors["player"].TraitInfo<PlayerColorPaletteInfo>();
+			var destPaletteInfo = destModData.DefaultRules.Actors["player"].TraitInfo<PlayerColorPaletteInfo>();
 			var destRemapIndex = destPaletteInfo.RemapIndex;
 			var shadowIndex = new int[] { };
 
diff --git a/OpenRA.Mods.Common/Widgets/Logic/Editor/LayerSelectorLogic.cs b/OpenRA.Mods.Common/Widgets/Logic/Editor/LayerSelectorLogic.cs
index 63c697dde6..985eb1fa77 100644
--- a/OpenRA.Mods.Common/Widgets/Logic/Editor/LayerSelectorLogic.cs
+++ b/OpenRA.Mods.Common/Widgets/Logic/Editor/LayerSelectorLogic.cs
@@ -19,7 +19,6 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 	public class LayerSelectorLogic : ChromeLogic
 	{
 		readonly EditorViewportControllerWidget editor;
-		readonly World world;
 		readonly WorldRenderer worldRenderer;
 
 		readonly ScrollPanelWidget layerTemplateList;
@@ -29,8 +28,6 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 		public LayerSelectorLogic(Widget widget, WorldRenderer worldRenderer)
 		{
 			this.worldRenderer = worldRenderer;
-			world = worldRenderer.World;
-
 			editor = widget.Parent.Get<EditorViewportControllerWidget>("MAP_EDITOR");
 
 			layerTemplateList = widget.Get<ScrollPanelWidget>("LAYERTEMPLATE_LIST");
@@ -60,7 +57,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 				layerPreview.GetPalette = () => resource.Palette;
 
 				var variant = resource.Variants.FirstOrDefault();
-				var sequenceProvider = rules.Sequences[world.TileSet.Id];
+				var sequenceProvider = rules.Sequences;
 				var sequence = sequenceProvider.GetSequence("resources", variant);
 				var frame = sequence.Frames != null ? sequence.Frames.Last() : resource.MaxDensity - 1;
 				layerPreview.GetSprite = () => sequence.GetSprite(frame);
diff --git a/OpenRA.Mods.Common/Widgets/Logic/Editor/NewMapLogic.cs b/OpenRA.Mods.Common/Widgets/Logic/Editor/NewMapLogic.cs
index 45fe326b1e..00067aa452 100644
--- a/OpenRA.Mods.Common/Widgets/Logic/Editor/NewMapLogic.cs
+++ b/OpenRA.Mods.Common/Widgets/Logic/Editor/NewMapLogic.cs
@@ -20,14 +20,14 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 		Widget panel;
 
 		[ObjectCreator.UseCtor]
-		public NewMapLogic(Action onExit, Action<string> onSelect, Widget widget, World world)
+		public NewMapLogic(Action onExit, Action<string> onSelect, Widget widget, World world, ModData modData)
 		{
 			panel = widget;
 
 			panel.Get<ButtonWidget>("CANCEL_BUTTON").OnClick = () => { Ui.CloseWindow(); onExit(); };
 
 			var tilesetDropDown = panel.Get<DropDownButtonWidget>("TILESET");
-			var tilesets = world.Map.Rules.TileSets.Select(t => t.Key).ToList();
+			var tilesets = modData.DefaultTileSets.Select(t => t.Key).ToList();
 			Func<string, ScrollItemWidget, ScrollItemWidget> setupItem = (option, template) =>
 			{
 				var item = ScrollItemWidget.Setup(template,
@@ -55,7 +55,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 				height = Math.Max(2, height);
 
 				var maxTerrainHeight = world.Map.Grid.MaximumTerrainHeight;
-				var tileset = world.Map.Rules.TileSets[tilesetDropDown.Text];
+				var tileset = modData.DefaultTileSets[tilesetDropDown.Text];
 				var map = new Map(Game.ModData, tileset, width + 2, height + maxTerrainHeight + 2);
 
 				var tl = new PPos(1, 1);
diff --git a/OpenRA.Mods.Common/Widgets/Logic/Editor/TileSelectorLogic.cs b/OpenRA.Mods.Common/Widgets/Logic/Editor/TileSelectorLogic.cs
index 257e61aa8f..6ca7384cdd 100644
--- a/OpenRA.Mods.Common/Widgets/Logic/Editor/TileSelectorLogic.cs
+++ b/OpenRA.Mods.Common/Widgets/Logic/Editor/TileSelectorLogic.cs
@@ -26,7 +26,7 @@ namespace OpenRA.Mods.Common.Widgets.Logic
 		public TileSelectorLogic(Widget widget, WorldRenderer worldRenderer)
 		{
 			var rules = worldRenderer.World.Map.Rules;
-			var tileset = rules.TileSets[worldRenderer.World.Map.Tileset];
+			var tileset = rules.TileSet;
 
 			editor = widget.Parent.Get<EditorViewportControllerWidget>("MAP_EDITOR");
 			panel = widget.Get<ScrollPanelWidget>("TILETEMPLATE_LIST");
diff --git a/OpenRA.Mods.Common/Widgets/TerrainTemplatePreviewWidget.cs b/OpenRA.Mods.Common/Widgets/TerrainTemplatePreviewWidget.cs
index 777f477171..b34764539f 100644
--- a/OpenRA.Mods.Common/Widgets/TerrainTemplatePreviewWidget.cs
+++ b/OpenRA.Mods.Common/Widgets/TerrainTemplatePreviewWidget.cs
@@ -48,14 +48,14 @@ namespace OpenRA.Mods.Common.Widgets
 		public TerrainTemplatePreviewWidget(WorldRenderer worldRenderer, World world)
 		{
 			this.worldRenderer = worldRenderer;
-			tileset = world.Map.Rules.TileSets[world.Map.Tileset];
+			tileset = world.Map.Rules.TileSet;
 		}
 
 		protected TerrainTemplatePreviewWidget(TerrainTemplatePreviewWidget other)
 			: base(other)
 		{
 			worldRenderer = other.worldRenderer;
-			tileset = other.worldRenderer.World.Map.Rules.TileSets[other.worldRenderer.World.Map.Tileset];
+			tileset = other.worldRenderer.World.Map.Rules.TileSet;
 			Template = other.Template;
 			GetScale = other.GetScale;
 		}
diff --git a/OpenRA.Mods.D2k/UtilityCommands/D2kMapImporter.cs b/OpenRA.Mods.D2k/UtilityCommands/D2kMapImporter.cs
index d15333cc62..3656ad15fd 100644
--- a/OpenRA.Mods.D2k/UtilityCommands/D2kMapImporter.cs
+++ b/OpenRA.Mods.D2k/UtilityCommands/D2kMapImporter.cs
@@ -308,7 +308,7 @@ namespace OpenRA.Mods.D2k.UtilityCommands
 		{
 			mapSize = new Size(stream.ReadUInt16(), stream.ReadUInt16());
 
-			tileSet = rules.TileSets["ARRAKIS"];
+			tileSet = Game.ModData.DefaultTileSets["ARRAKIS"];
 
 			map = new Map(Game.ModData, tileSet, mapSize.Width + 2 * MapCordonWidth, mapSize.Height + 2 * MapCordonWidth)
 			{
diff --git a/OpenRA.Mods.D2k/UtilityCommands/ImportD2kMapCommand.cs b/OpenRA.Mods.D2k/UtilityCommands/ImportD2kMapCommand.cs
index e57c34c162..b26530ba71 100644
--- a/OpenRA.Mods.D2k/UtilityCommands/ImportD2kMapCommand.cs
+++ b/OpenRA.Mods.D2k/UtilityCommands/ImportD2kMapCommand.cs
@@ -30,8 +30,7 @@ namespace OpenRA.Mods.D2k.UtilityCommands
 			// HACK: The engine code assumes that Game.modData is set.
 			Game.ModData = modData;
 
-			var rules = modData.RulesetCache.Load(modData.DefaultFileSystem);
-
+			var rules = Ruleset.LoadDefaultsForTileSet(modData, "ARRAKIS");
 			var map = D2kMapImporter.Import(args[1], modData.Manifest.Mod.Id, args[2], rules);
 
 			if (map == null)
diff --git a/OpenRA.Mods.TS/UtilityCommands/ImportTSMapCommand.cs b/OpenRA.Mods.TS/UtilityCommands/ImportTSMapCommand.cs
index 16d4477e55..c8f2c1f53b 100644
--- a/OpenRA.Mods.TS/UtilityCommands/ImportTSMapCommand.cs
+++ b/OpenRA.Mods.TS/UtilityCommands/ImportTSMapCommand.cs
@@ -228,7 +228,7 @@ namespace OpenRA.Mods.TS.UtilityCommands
 
 			fullSize = new int2(iniSize[2], iniSize[3]);
 
-			var map = new Map(Game.ModData, modData.DefaultRules.TileSets[tileset], size.Width, size.Height);
+			var map = new Map(Game.ModData, modData.DefaultTileSets[tileset], size.Width, size.Height);
 			map.Title = basic.GetValue("Name", Path.GetFileNameWithoutExtension(filename));
 			map.Author = "Westwood Studios";
 			map.Bounds = new Rectangle(iniBounds[0], iniBounds[1], iniBounds[2], 2 * iniBounds[3] + 2 * iniBounds[1]);
@@ -243,7 +243,7 @@ namespace OpenRA.Mods.TS.UtilityCommands
 
 		void ReadTiles(Map map, IniFile file)
 		{
-			var tileset = Game.ModData.DefaultRules.TileSets[map.Tileset];
+			var tileset = Game.ModData.DefaultTileSets[map.Tileset];
 			var mapSection = file.GetSection("IsoMapPack5");
 
 			var data = Convert.FromBase64String(mapSection.Aggregate(string.Empty, (a, b) => a + b.Value));