diff --git a/OpenRA.Game/Graphics/Minimap.cs b/OpenRA.Game/Graphics/Minimap.cs
index c766273883..f81c6860b4 100644
--- a/OpenRA.Game/Graphics/Minimap.cs
+++ b/OpenRA.Game/Graphics/Minimap.cs
@@ -20,11 +20,12 @@ namespace OpenRA.Graphics
 	{
 		public static Bitmap TerrainBitmap(TileSet tileset, Map map, bool actualSize = false)
 		{
-			var width = map.Bounds.Width;
-			var height = map.Bounds.Height;
+			var b = map.Bounds;
+			var width = b.Width;
+			var height = b.Height;
 
 			if (!actualSize)
-				width = height = Exts.NextPowerOf2(Math.Max(map.Bounds.Width, map.Bounds.Height));
+				width = height = Exts.NextPowerOf2(Math.Max(b.Width, b.Height));
 
 			var terrain = new Bitmap(width, height);
 
@@ -37,15 +38,17 @@ namespace OpenRA.Graphics
 			{
 				var c = (int*)bitmapData.Scan0;
 
-				for (var x = 0; x < map.Bounds.Width; x++)
-					for (var y = 0; y < map.Bounds.Height; y++)
+				for (var x = 0; x < b.Width; x++)
+				{
+					for (var y = 0; y < b.Height; y++)
 					{
-						var mapX = x + map.Bounds.Left;
-						var mapY = y + map.Bounds.Top;
+						var mapX = x + b.Left;
+						var mapY = y + b.Top;
 						var type = tileset.GetTerrainInfo(mapTiles[mapX, mapY]);
 
 						*(c + (y * bitmapData.Stride >> 2) + x) = type.Color.ToArgb();
 					}
+				}
 			}
 
 			terrain.UnlockBits(bitmapData);
@@ -57,6 +60,7 @@ namespace OpenRA.Graphics
 		static Bitmap AddStaticResources(TileSet tileset, Map map, Ruleset resourceRules, Bitmap terrainBitmap)
 		{
 			var terrain = new Bitmap(terrainBitmap);
+			var b = map.Bounds;
 
 			var bitmapData = terrain.LockBits(terrain.Bounds(),
 				ImageLockMode.ReadWrite, PixelFormat.Format32bppArgb);
@@ -65,11 +69,12 @@ namespace OpenRA.Graphics
 			{
 				var c = (int*)bitmapData.Scan0;
 
-				for (var x = 0; x < map.Bounds.Width; x++)
-					for (var y = 0; y < map.Bounds.Height; y++)
+				for (var x = 0; x < b.Width; x++)
+				{
+					for (var y = 0; y < b.Height; y++)
 					{
-						var mapX = x + map.Bounds.Left;
-						var mapY = y + map.Bounds.Top;
+						var mapX = x + b.Left;
+						var mapY = y + b.Top;
 						if (map.MapResources.Value[mapX, mapY].Type == 0)
 							continue;
 
@@ -82,6 +87,7 @@ namespace OpenRA.Graphics
 
 						*(c + (y * bitmapData.Stride >> 2) + x) = tileset[tileset.GetTerrainIndex(res)].Color.ToArgb();
 					}
+				}
 			}
 
 			terrain.UnlockBits(bitmapData);
@@ -92,7 +98,9 @@ namespace OpenRA.Graphics
 		public static Bitmap CustomTerrainBitmap(World world)
 		{
 			var map = world.Map;
-			var size = Exts.NextPowerOf2(Math.Max(map.Bounds.Width, map.Bounds.Height));
+			var b = map.Bounds;
+
+			var size = Exts.NextPowerOf2(Math.Max(b.Width, b.Height));
 			var bitmap = new Bitmap(size, size);
 			var bitmapData = bitmap.LockBits(bitmap.Bounds(),
 				ImageLockMode.ReadWrite, PixelFormat.Format32bppArgb);
@@ -101,16 +109,19 @@ namespace OpenRA.Graphics
 			{
 				var c = (int*)bitmapData.Scan0;
 
-				for (var x = 0; x < map.Bounds.Width; x++)
-					for (var y = 0; y < map.Bounds.Height; y++)
+				for (var x = 0; x < b.Width; x++)
+				{
+					for (var y = 0; y < b.Height; y++)
 					{
-						var mapX = x + map.Bounds.Left;
-						var mapY = y + map.Bounds.Top;
+						var mapX = x + b.Left;
+						var mapY = y + b.Top;
 						var custom = map.CustomTerrain[mapX, mapY];
 						if (custom == -1)
 							continue;
+
 						*(c + (y * bitmapData.Stride >> 2) + x) = world.TileSet[custom].Color.ToArgb();
 					}
+				}
 			}
 
 			bitmap.UnlockBits(bitmapData);
@@ -120,7 +131,9 @@ namespace OpenRA.Graphics
 		public static Bitmap ActorsBitmap(World world)
 		{
 			var map = world.Map;
-			var size = Exts.NextPowerOf2(Math.Max(map.Bounds.Width, map.Bounds.Height));
+			var b = map.Bounds;
+
+			var size = Exts.NextPowerOf2(Math.Max(b.Width, b.Height));
 			var bitmap = new Bitmap(size, size);
 			var bitmapData = bitmap.LockBits(bitmap.Bounds(),
 				ImageLockMode.ReadWrite, PixelFormat.Format32bppArgb);
@@ -136,8 +149,11 @@ namespace OpenRA.Graphics
 
 					var color = t.Trait.RadarSignatureColor(t.Actor);
 					foreach (var cell in t.Trait.RadarSignatureCells(t.Actor))
-						if (world.Map.Contains(cell))
-							*(c + ((cell.Y - world.Map.Bounds.Top) * bitmapData.Stride >> 2) + cell.X - world.Map.Bounds.Left) = color.ToArgb();
+					{
+						var uv = Map.CellToMap(map.TileShape, cell);
+						if (b.Contains(uv.X, uv.Y))
+							*(c + ((uv.Y - b.Top) * bitmapData.Stride >> 2) + uv.X - b.Left) = color.ToArgb();
+					}
 				}
 			}
 
@@ -148,7 +164,9 @@ namespace OpenRA.Graphics
 		public static Bitmap ShroudBitmap(World world)
 		{
 			var map = world.Map;
-			var size = Exts.NextPowerOf2(Math.Max(map.Bounds.Width, map.Bounds.Height));
+			var b = map.Bounds;
+
+			var size = Exts.NextPowerOf2(Math.Max(b.Width, b.Height));
 			var bitmap = new Bitmap(size, size);
 			if (world.RenderPlayer == null)
 				return bitmap;
@@ -158,20 +176,20 @@ namespace OpenRA.Graphics
 
 			var shroud = Color.Black.ToArgb();
 			var fog = Color.FromArgb(128, Color.Black).ToArgb();
+			var offset = new CVec(b.Left, b.Top);
 
 			unsafe
 			{
 				var c = (int*)bitmapData.Scan0;
 
-				for (var x = 0; x < map.Bounds.Width; x++)
-					for (var y = 0; y < map.Bounds.Height; y++)
-					{
-						var p = new CPos(x + map.Bounds.Left, y + map.Bounds.Top);
-						if (world.ShroudObscures(p))
-							*(c + (y * bitmapData.Stride >> 2) + x) = shroud;
-						else if (world.FogObscures(p))
-							*(c + (y * bitmapData.Stride >> 2) + x) = fog;
-					}
+				foreach (var cell in map.Cells)
+				{
+					var uv = Map.CellToMap(map.TileShape, cell) - offset;
+					if (world.ShroudObscures(cell))
+						*(c + (uv.Y * bitmapData.Stride >> 2) + uv.X) = shroud;
+					else if (world.FogObscures(cell))
+						*(c + (uv.Y * bitmapData.Stride >> 2) + uv.X) = fog;
+				}
 			}
 
 			bitmap.UnlockBits(bitmapData);
diff --git a/OpenRA.Game/Graphics/TerrainRenderer.cs b/OpenRA.Game/Graphics/TerrainRenderer.cs
index 11dc2f142d..c194be88e3 100644
--- a/OpenRA.Game/Graphics/TerrainRenderer.cs
+++ b/OpenRA.Game/Graphics/TerrainRenderer.cs
@@ -44,11 +44,12 @@ namespace OpenRA.Graphics
 		{
 			var verticesPerRow = 4*map.Bounds.Width;
 			var cells = viewport.VisibleCells;
-			var firstRow = cells.TopLeft.Y - map.Bounds.Top;
-			var lastRow = cells.BottomRight.Y - map.Bounds.Top + 1;
+			var shape = wr.world.Map.TileShape;
 
-			if (lastRow < 0 || firstRow > map.Bounds.Height)
-				return;
+			// Only draw the rows that are visible.
+			// VisibleCells is clamped to the map, so additional checks are unnecessary
+			var firstRow = Map.CellToMap(shape, cells.TopLeft).Y - map.Bounds.Top;
+			var lastRow = Map.CellToMap(shape, cells.BottomRight).Y - map.Bounds.Top + 1;
 
 			Game.Renderer.WorldSpriteRenderer.DrawVertexBuffer(
 				vertexBuffer, verticesPerRow * firstRow, verticesPerRow * (lastRow - firstRow),
diff --git a/OpenRA.Game/Graphics/Viewport.cs b/OpenRA.Game/Graphics/Viewport.cs
index 3c181f6480..83970ec606 100644
--- a/OpenRA.Game/Graphics/Viewport.cs
+++ b/OpenRA.Game/Graphics/Viewport.cs
@@ -92,8 +92,8 @@ namespace OpenRA.Graphics
 			var b = map.Bounds;
 
 			// Expand to corners of cells
-			var tl = wr.ScreenPxPosition(map.CenterOfCell(new CPos(b.Left, b.Top)) - new WVec(512, 512, 0));
-			var br = wr.ScreenPxPosition(map.CenterOfCell(new CPos(b.Right, b.Bottom)) + new WVec(511, 511, 0));
+			var tl = wr.ScreenPxPosition(map.CenterOfCell(Map.MapToCell(map.TileShape, new CPos(b.Left, b.Top))) - new WVec(512, 512, 0));
+			var br = wr.ScreenPxPosition(map.CenterOfCell(Map.MapToCell(map.TileShape, new CPos(b.Right, b.Bottom))) + new WVec(511, 511, 0));
 			mapBounds = Rectangle.FromLTRB(tl.X, tl.Y, br.X, br.Y);
 
 			CenterLocation = (tl + br) / 2;
@@ -138,8 +138,12 @@ namespace OpenRA.Graphics
 		{
 			get
 			{
-				var ctl = worldRenderer.world.Map.CenterOfCell(VisibleCells.TopLeft) - new WVec(512, 512, 0);
-				var cbr = worldRenderer.world.Map.CenterOfCell(VisibleCells.BottomRight) + new WVec(511, 511, 0);
+				// Visible rectangle in world coordinates (expanded to the corners of the cells)
+				var map = worldRenderer.world.Map;
+				var ctl = map.CenterOfCell(VisibleCells.TopLeft) - new WVec(512, 512, 0);
+				var cbr = map.CenterOfCell(VisibleCells.BottomRight) + new WVec(512, 512, 0);
+
+				// Convert to screen coordinates
 				var tl = WorldToViewPx(worldRenderer.ScreenPxPosition(ctl)).Clamp(ScreenClip);
 				var br = WorldToViewPx(worldRenderer.ScreenPxPosition(cbr)).Clamp(ScreenClip);
 				return Rectangle.FromLTRB(tl.X, tl.Y, br.X, br.Y);
@@ -152,12 +156,16 @@ namespace OpenRA.Graphics
 			{
 				if (cellsDirty)
 				{
-					// Calculate the intersection of the visible rectangle and the map.
+					// Visible rectangle in map coordinates
 					var map = worldRenderer.world.Map;
-					var tl = map.Clamp(map.CellContaining(worldRenderer.Position(TopLeft)) - new CVec(1, 1));
-					var br = map.Clamp(map.CellContaining(worldRenderer.Position(BottomRight)));
+					var ctl = Map.CellToMap(map.TileShape, map.CellContaining(worldRenderer.Position(TopLeft)));
+					var cbr = Map.CellToMap(map.TileShape, map.CellContaining(worldRenderer.Position(BottomRight)));
 
-					cells = new CellRegion(tl, br);
+					// Add a 2 cell cordon to prevent holes, then convert back to cell coordinates
+					var tl = map.Clamp(Map.MapToCell(map.TileShape, ctl - new CVec(2, 2)));
+					var br = map.Clamp(Map.MapToCell(map.TileShape, cbr + new CVec(2, 2)));
+
+					cells = new CellRegion(map.TileShape, tl, br);
 					cellsDirty = false;
 				}
 
diff --git a/OpenRA.Game/Manifest.cs b/OpenRA.Game/Manifest.cs
index 194dadca8c..ece91098dc 100644
--- a/OpenRA.Game/Manifest.cs
+++ b/OpenRA.Game/Manifest.cs
@@ -16,6 +16,8 @@ using OpenRA.Primitives;
 
 namespace OpenRA
 {
+	public enum TileShape { Rectangle, Diamond }
+
 	// Describes what is to be loaded in order to run a mod
 	public class Manifest
 	{
@@ -33,6 +35,7 @@ namespace OpenRA
 		public readonly Dictionary<string, Pair<string, int>> Fonts;
 		public readonly Size TileSize = new Size(24, 24);
 		public readonly string NewsUrl;
+		public readonly TileShape TileShape = TileShape.Rectangle;
 
 		public Manifest(string mod)
 		{
@@ -77,6 +80,9 @@ namespace OpenRA
 			if (yaml.ContainsKey("TileSize"))
 				TileSize = FieldLoader.GetValue<Size>("TileSize", yaml["TileSize"].Value);
 
+			if (yaml.ContainsKey("TileShape"))
+				TileShape = FieldLoader.GetValue<TileShape>("TileShape", yaml["TileShape"].Value);
+
 			// Allow inherited mods to import parent maps.
 			var compat = new List<string>();
 			compat.Add(mod);
diff --git a/OpenRA.Game/Map/CellLayer.cs b/OpenRA.Game/Map/CellLayer.cs
index 7f973b8902..3c0f444840 100644
--- a/OpenRA.Game/Map/CellLayer.cs
+++ b/OpenRA.Game/Map/CellLayer.cs
@@ -20,22 +20,24 @@ namespace OpenRA
 	public class CellLayer<T> : IEnumerable<T>
 	{
 		public readonly Size Size;
+		public readonly TileShape Shape;
 		T[] entries;
 
 		public CellLayer(Map map)
-			: this(new Size(map.MapSize.X, map.MapSize.Y)) { }
+			: this(map.TileShape, new Size(map.MapSize.X, map.MapSize.Y)) { }
 
-		public CellLayer(Size size)
+		public CellLayer(TileShape shape, Size size)
 		{
 			Size = size;
+			Shape = shape;
 			entries = new T[size.Width * size.Height];
 		}
 
 		// Resolve an array index from cell coordinates
 		int Index(CPos cell)
 		{
-			// This will eventually define a distinct case for diagonal cell grids
-			return cell.Y * Size.Width + cell.X;
+			var uv = Map.CellToMap(Shape, cell);
+			return uv.Y * Size.Width + uv.X;
 		}
 
 		/// <summary>Gets or sets the <see cref="OpenRA.CellLayer"/> using cell coordinates</summary>
@@ -90,7 +92,7 @@ namespace OpenRA
 		/// <summary>Create a new layer by resizing another layer.  New cells are filled with defaultValue.</summary>
 		public static CellLayer<T> Resize<T>(CellLayer<T> layer, Size newSize, T defaultValue)
 		{
-			var result = new CellLayer<T>(newSize);
+			var result = new CellLayer<T>(layer.Shape, newSize);
 			var width = Math.Min(layer.Size.Width, newSize.Width);
 			var height = Math.Min(layer.Size.Height, newSize.Height);
 
diff --git a/OpenRA.Game/Map/CellRegion.cs b/OpenRA.Game/Map/CellRegion.cs
index 3cdccc7fbe..ce7316ecd1 100644
--- a/OpenRA.Game/Map/CellRegion.cs
+++ b/OpenRA.Game/Map/CellRegion.cs
@@ -23,25 +23,36 @@ namespace OpenRA
 		// Corners of the region
 		public readonly CPos TopLeft;
 		public readonly CPos BottomRight;
+		readonly TileShape shape;
 
 		// Corners in map coordinates
-		// Defined for forward compatibility with diagonal cell grids
+		// These will only equal TopLeft and BottomRight for TileShape.Rectangular
 		readonly CPos mapTopLeft;
 		readonly CPos mapBottomRight;
 
-		public CellRegion(CPos topLeft, CPos bottomRight)
+		public CellRegion(TileShape shape, CPos topLeft, CPos bottomRight)
 		{
+			this.shape = shape;
 			TopLeft = topLeft;
 			BottomRight = bottomRight;
 
-			mapTopLeft = TopLeft;
-			mapBottomRight = BottomRight;
+			mapTopLeft = Map.CellToMap(shape, TopLeft);
+			mapBottomRight = Map.CellToMap(shape, BottomRight);
+		}
+
+		/// <summary>Expand the specified region with an additional cordon. This may expand the region outside the map borders.</summary>
+		public static CellRegion Expand(CellRegion region, int cordon)
+		{
+			var offset = new CVec(cordon, cordon);
+			var tl = Map.MapToCell(region.shape, Map.CellToMap(region.shape, region.TopLeft) - offset);
+			var br = Map.MapToCell(region.shape, Map.CellToMap(region.shape, region.BottomRight) + offset);
+
+			return new CellRegion(region.shape, tl, br);
 		}
 
 		public bool Contains(CPos cell)
 		{
-			// Defined for forward compatibility with diagonal cell grids
-			var uv = cell;
+			var uv = Map.CellToMap(shape, cell);
 			return uv.X >= mapTopLeft.X && uv.X <= mapBottomRight.X && uv.Y >= mapTopLeft.Y && uv.Y <= mapBottomRight.Y;
 		}
 
@@ -93,7 +104,7 @@ namespace OpenRA
 				v = r.mapTopLeft.Y;
 			}
 
-			public CPos Current { get { return new CPos(u, v); } }
+			public CPos Current { get { return Map.MapToCell(r.shape, new CPos(u, v)); } }
 			object IEnumerator.Current { get { return Current; } }
 			public void Dispose() { }
 		}
diff --git a/OpenRA.Game/Map/Map.cs b/OpenRA.Game/Map/Map.cs
index 8cbe791316..484362f138 100644
--- a/OpenRA.Game/Map/Map.cs
+++ b/OpenRA.Game/Map/Map.cs
@@ -76,6 +76,8 @@ namespace OpenRA
 		public bool AllowStartUnitConfig = true;
 		public Bitmap CustomPreview;
 
+		public readonly TileShape TileShape;
+
 		[FieldLoader.LoadUsing("LoadOptions")]
 		public MapOptions Options;
 
@@ -125,11 +127,12 @@ namespace OpenRA
 		public static Map FromTileset(TileSet tileset)
 		{
 			var size = new Size(1, 1);
+			var tileShape = Game.modData.Manifest.TileShape;
 			var tileRef = new TerrainTile(tileset.Templates.First().Key, (byte)0);
 
 			var makeMapTiles =  Exts.Lazy(() =>
 			{
-				var ret = new CellLayer<TerrainTile>(size);
+				var ret = new CellLayer<TerrainTile>(tileShape, size);
 				ret.Clear(tileRef);
 				return ret;
 			});
@@ -142,7 +145,7 @@ namespace OpenRA
 				MapSize = new int2(size),
 				Tileset = tileset.Id,
 				Options = new MapOptions(),
-				MapResources = Exts.Lazy(() => new CellLayer<ResourceTile>(size)),
+				MapResources = Exts.Lazy(() => new CellLayer<ResourceTile>(tileShape, size)),
 				MapTiles = makeMapTiles,
 				Actors = Exts.Lazy(() => new Dictionary<string, ActorReference>()),
 				Smudges = Exts.Lazy(() => new List<SmudgeReference>())
@@ -242,6 +245,7 @@ namespace OpenRA
 
 			MapTiles = Exts.Lazy(() => LoadMapTiles());
 			MapResources = Exts.Lazy(() => LoadResourceTiles());
+			TileShape = Game.modData.Manifest.TileShape;
 
 			// The Uid is calculated from the data on-disk, so
 			// format changes must be flushed to disk.
@@ -262,9 +266,9 @@ namespace OpenRA
 			rules = Exts.Lazy(() => Game.modData.RulesetCache.LoadMapRules(this));
 			cachedTileSet = Exts.Lazy(() => Rules.TileSets[Tileset]);
 
-			var tl = new CPos(Bounds.Left, Bounds.Top);
-			var br = new CPos(Bounds.Right - 1, Bounds.Bottom - 1);
-			Cells = new CellRegion(tl, br);
+			var tl = Map.MapToCell(TileShape, new CPos(Bounds.Left, Bounds.Top));
+			var br = Map.MapToCell(TileShape, new CPos(Bounds.Right - 1, Bounds.Bottom - 1));
+			Cells = new CellRegion(TileShape, tl, br);
 
 			CustomTerrain = new CellLayer<int>(this);
 			foreach (var cell in Cells)
@@ -465,17 +469,79 @@ namespace OpenRA
 
 		public bool Contains(CPos cell)
 		{
-			return Bounds.Contains(cell.X, cell.Y);
+			var uv = CellToMap(TileShape, cell);
+			return Bounds.Contains(uv.X, uv.Y);
 		}
 
-		public WPos CenterOfCell(CPos c)
+		public WPos CenterOfCell(CPos cell)
 		{
-			return new WPos(1024 * c.X + 512, 1024 * c.Y + 512, 0);
+			if (TileShape == TileShape.Rectangle)
+				return new WPos(1024 * cell.X + 512, 1024 * cell.Y + 512, 0);
+
+			// Convert from diamond cell position (x, y) to world position (u, v):
+			// (a) Consider the relationships:
+			//  - Center of origin cell is (512, 512)
+			//  - +x adds (512, 512) to world pos
+			//  - +y adds (-512, 512) to world pos
+			// (b) Therefore:
+			//  - ax + by adds (a - b) * 512 + 512 to u
+			//  - ax + by adds (a + b) * 512 + 512 to v
+			return new WPos(512 * (cell.X - cell.Y + 1), 512 * (cell.X + cell.Y + 1), 0);
 		}
 
 		public CPos CellContaining(WPos pos)
 		{
-			return new CPos(pos.X / 1024, pos.Y / 1024);
+			if (TileShape == TileShape.Rectangle)
+				return new CPos(pos.X / 1024, pos.Y / 1024);
+
+			// Convert from world position to diamond cell position:
+			// (a) Subtract (512, 512) to move the rotation center to the middle of the corner cell
+			// (b) Rotate axes by -pi/4
+			// (c) Add 512 to x (but not y) to realign the cell
+			// (d) Divide by 1024 to find final cell coords
+			var u = (pos.Y + pos.X - 512) / 1024;
+			var v = (pos.Y - pos.X) / 1024;
+			return new CPos(u, v);
+		}
+
+		public static CPos MapToCell(TileShape shape, CPos map)
+		{
+			if (shape == TileShape.Rectangle)
+				return map;
+
+			// Convert from rectangular map position to diamond cell position
+			//  - The staggered rows make this fiddly (hint: draw a diagram!)
+			// (a) Consider the relationships:
+			//  - +1u (even -> odd) adds (1, -1) to (x, y)
+			//  - +1v (even -> odd) adds (1, 0) to (x, y)
+			//  - +1v (odd -> even) adds (0, 1) to (x, y)
+			// (b) Therefore:
+			//  - au + 2bv adds (a + b) to (x, y)
+			//  - a correction factor is added if v is odd
+			var offset = (map.Y & 1) == 1 ? 1 : 0;
+			var y = (map.Y - offset) / 2 - map.X;
+			var x = map.Y - y;
+			return new CPos(x, y);
+		}
+
+		public static CPos CellToMap(TileShape shape, CPos cell)
+		{
+			if (shape == TileShape.Rectangle)
+				return cell;
+
+			// Convert from diamond cell (x, y) position to rectangular map position (u, v)
+			//  - The staggered rows make this fiddly (hint: draw a diagram!)
+			// (a) Consider the relationships:
+			//  - +1x (even -> odd) adds (0, 1) to (u, v)
+			//  - +1x (odd -> even) adds (1, 1) to (u, v)
+			//  - +1y (even -> odd) adds (-1, 1) to (u, v)
+			//  - +1y (odd -> even) adds (0, 1) to (u, v)
+			// (b) Therefore:
+			//  - ax + by adds (a - b)/2 to u (only even increments count)
+			//  - ax + by adds a + b to v
+			var u = (cell.X - cell.Y) / 2;
+			var v = cell.X + cell.Y;
+			return new CPos(u, v);
 		}
 
 		public int FacingBetween(CPos cell, CPos towards, int fallbackfacing)
@@ -497,7 +563,10 @@ namespace OpenRA
 		public void ResizeCordon(int left, int top, int right, int bottom)
 		{
 			Bounds = Rectangle.FromLTRB(left, top, right, bottom);
-			Cells = new CellRegion(new CPos(Bounds.Left, Bounds.Top), new CPos(Bounds.Right - 1, Bounds.Bottom - 1));
+
+			var tl = Map.MapToCell(TileShape, new CPos(Bounds.Left, Bounds.Top));
+			var br = Map.MapToCell(TileShape, new CPos(Bounds.Right - 1, Bounds.Bottom - 1));
+			Cells = new CellRegion(TileShape, tl, br);
 		}
 
 		string ComputeHash()
@@ -597,17 +666,18 @@ namespace OpenRA
 			return cachedTileSet.Value[GetTerrainIndex(cell)];
 		}
 
-		public CPos Clamp(CPos xy)
+		public CPos Clamp(CPos cell)
 		{
-			var r = Bounds;
-			return xy.Clamp(new Rectangle(r.X, r.Y, r.Width - 1, r.Height - 1));
+			var bounds = new Rectangle(Bounds.X, Bounds.Y, Bounds.Width - 1, Bounds.Height - 1);
+			return MapToCell(TileShape, CellToMap(TileShape, cell).Clamp(bounds));
 		}
 
 		public CPos ChooseRandomCell(MersenneTwister rand)
 		{
-			return new CPos(
-				rand.Next(Bounds.Left, Bounds.Right),
-				rand.Next(Bounds.Top, Bounds.Bottom));
+			var x = rand.Next(Bounds.Left, Bounds.Right);
+			var y = rand.Next(Bounds.Top, Bounds.Bottom);
+
+			return MapToCell(TileShape, new CPos(x, y));
 		}
 
 		public CPos ChooseRandomEdgeCell(MersenneTwister rand)
@@ -615,15 +685,16 @@ namespace OpenRA
 			var isX = rand.Next(2) == 0;
 			var edge = rand.Next(2) == 0;
 
-			return new CPos(
-				isX ? rand.Next(Bounds.Left, Bounds.Right) : (edge ? Bounds.Left : Bounds.Right),
-				!isX ? rand.Next(Bounds.Top, Bounds.Bottom) : (edge ? Bounds.Top : Bounds.Bottom));
+			var x = isX ? rand.Next(Bounds.Left, Bounds.Right) : (edge ? Bounds.Left : Bounds.Right);
+			var y = !isX ? rand.Next(Bounds.Top, Bounds.Bottom) :  (edge ? Bounds.Top : Bounds.Bottom);
+
+			return MapToCell(TileShape, new CPos(x, y));
 		}
 
 		public WRange DistanceToEdge(WPos pos, WVec dir)
 		{
-			var tl = CenterOfCell(new CPos(Bounds.Left, Bounds.Top)) - new WVec(512, 512, 0);
-			var br = CenterOfCell(new CPos(Bounds.Right, Bounds.Bottom)) + new WVec(511, 511, 0);
+			var tl = CenterOfCell(Cells.TopLeft) - new WVec(512, 512, 0);
+			var br = CenterOfCell(Cells.BottomRight) + new WVec(511, 511, 0);
 			var x = dir.X == 0 ? int.MaxValue : ((dir.X < 0 ? tl.X : br.X) - pos.X) / dir.X;
 			var y = dir.Y == 0 ? int.MaxValue : ((dir.Y < 0 ? tl.Y : br.Y) - pos.Y) / dir.Y;
 			return new WRange(Math.Min(x, y) * dir.Length);
diff --git a/OpenRA.Game/Widgets/MapPreviewWidget.cs b/OpenRA.Game/Widgets/MapPreviewWidget.cs
index 384bd8b316..c70aab3c0f 100644
--- a/OpenRA.Game/Widgets/MapPreviewWidget.cs
+++ b/OpenRA.Game/Widgets/MapPreviewWidget.cs
@@ -129,9 +129,10 @@ namespace OpenRA.Widgets
 				tooltipContainer.Value.RemoveTooltip();
 		}
 
-		public int2 ConvertToPreview(CPos point)
+		public int2 ConvertToPreview(CPos cell)
 		{
 			var preview = Preview();
+			var point = Map.CellToMap(preview.Map.TileShape, cell);
 			var dx = (int)(previewScale * (point.X - preview.Bounds.Left));
 			var dy = (int)(previewScale * (point.Y - preview.Bounds.Top));
 			return new int2(mapRect.X + dx, mapRect.Y + dy);
diff --git a/OpenRA.Mods.RA/Move/PathSearch.cs b/OpenRA.Mods.RA/Move/PathSearch.cs
index 1b61a86814..93a3ccb2fb 100755
--- a/OpenRA.Mods.RA/Move/PathSearch.cs
+++ b/OpenRA.Mods.RA/Move/PathSearch.cs
@@ -287,7 +287,7 @@ namespace OpenRA.Mods.RA.Move
 			while (CellInfoPool.Count > 0)
 			{
 				var cellInfo = GetFromPool();
-				if (cellInfo.Size != mapSize)
+				if (cellInfo.Size != mapSize || cellInfo.Shape != self.World.Map.TileShape)
 				{
 					Log.Write("debug", "Discarding old pooled CellInfo of wrong size.");
 					continue;
diff --git a/OpenRA.Mods.RA/ShroudRenderer.cs b/OpenRA.Mods.RA/ShroudRenderer.cs
index 302d466984..10a44b1fc5 100644
--- a/OpenRA.Mods.RA/ShroudRenderer.cs
+++ b/OpenRA.Mods.RA/ShroudRenderer.cs
@@ -177,19 +177,19 @@ namespace OpenRA.Mods.RA
 			return useExtendedIndex ? u ^ uside : u & 0x0F;
 		}
 
-		static int ObserverShroudedEdges(CPos p, Rectangle bounds, bool useExtendedIndex)
+		static int ObserverShroudedEdges(Map map, CPos p, bool useExtendedIndex)
 		{
 			var u = 0;
-			if (p.Y == bounds.Top) u |= 0x13;
-			if (p.X == bounds.Right - 1) u |= 0x26;
-			if (p.Y == bounds.Bottom - 1) u |= 0x4C;
-			if (p.X == bounds.Left)	u |= 0x89;
+			if (!map.Contains(p + new CVec(0, -1))) u |= 0x13;
+			if (!map.Contains(p + new CVec(1, 0))) u |= 0x26;
+			if (!map.Contains(p + new CVec(0, 1))) u |= 0x4C;
+			if (!map.Contains(p + new CVec(-1, 0))) u |= 0x89;
 
 			var uside = u & 0x0F;
-			if (p.X == bounds.Left && p.Y == bounds.Top) u |= 0x01;
-			if (p.X == bounds.Right - 1 && p.Y == bounds.Top) u |= 0x02;
-			if (p.X == bounds.Right - 1 && p.Y == bounds.Bottom - 1) u |= 0x04;
-			if (p.X == bounds.Left && p.Y == bounds.Bottom - 1) u |= 0x08;
+			if (!map.Contains(p + new CVec(-1, -1))) u |= 0x01;
+			if (!map.Contains(p + new CVec(1, -1))) u |= 0x02;
+			if (!map.Contains(p + new CVec(1, 1))) u |= 0x04;
+			if (!map.Contains(p + new CVec(-1, 1))) u |= 0x08;
 
 			return useExtendedIndex ? u ^ uside : u & 0x0F;
 		}
@@ -197,11 +197,19 @@ namespace OpenRA.Mods.RA
 		public void WorldLoaded(World w, WorldRenderer wr)
 		{
 			// Initialize tile cache
-			foreach (var cell in map.Cells)
+			// Adds a 1-cell border around the border to cover any sprites peeking outside the map
+			foreach (var cell in CellRegion.Expand(w.Map.Cells, 1))
 			{
 				var screen = wr.ScreenPosition(w.Map.CenterOfCell(cell));
 				var variant = Game.CosmeticRandom.Next(info.ShroudVariants.Length);
 				tiles[cell] = new ShroudTile(cell, screen, variant);
+
+				// Set the cells outside the border so they don't need to be touched again
+				if (!map.Contains(cell))
+				{
+					var index = info.UseExtendedIndex ? 240 : 15;
+					tiles[cell].Shroud = shroudSprites[variant * variantStride + spriteMap[index]];
+				}
 			}
 
 			fogPalette = wr.Palette(info.FogPalette);
@@ -229,7 +237,7 @@ namespace OpenRA.Mods.RA
 				foreach (var cell in map.Cells)
 				{
 					var t = tiles[cell];
-					var shrouded = ObserverShroudedEdges(t.Position, map.Bounds, info.UseExtendedIndex);
+					var shrouded = ObserverShroudedEdges(map, t.Position, info.UseExtendedIndex);
 
 					t.Shroud = shrouded != 0 ? shroudSprites[t.Variant * variantStride + spriteMap[shrouded]] : null;
 					t.Fog = shrouded != 0 ? fogSprites[t.Variant * variantStride + spriteMap[shrouded]] : null;
@@ -253,7 +261,7 @@ namespace OpenRA.Mods.RA
 		{
 			Update(shroud);
 
-			foreach (var cell in wr.Viewport.VisibleCells)
+			foreach (var cell in CellRegion.Expand(wr.Viewport.VisibleCells, 1))
 			{
 				var t = tiles[cell];
 
diff --git a/OpenRA.Mods.RA/Widgets/RadarWidget.cs b/OpenRA.Mods.RA/Widgets/RadarWidget.cs
index 960e484b5e..e7b4fdaa96 100755
--- a/OpenRA.Mods.RA/Widgets/RadarWidget.cs
+++ b/OpenRA.Mods.RA/Widgets/RadarWidget.cs
@@ -115,7 +115,7 @@ namespace OpenRA.Mods.RA.Widgets
 			var cell = MinimapPixelToCell(mi.Location);
 			var pos = world.Map.CenterOfCell(cell);
 			if ((mi.Event == MouseInputEvent.Down || mi.Event == MouseInputEvent.Move) && mi.Button == MouseButton.Left)
-				worldRenderer.Viewport.Center(world.Map.CenterOfCell(cell));
+				worldRenderer.Viewport.Center(pos);
 
 			if (mi.Event == MouseInputEvent.Down && mi.Button == MouseButton.Right)
 			{
@@ -242,8 +242,8 @@ namespace OpenRA.Mods.RA.Widgets
 
 		int2 CellToMinimapPixel(CPos p)
 		{
-			var mapOrigin = new CPos(world.Map.Bounds.Left, world.Map.Bounds.Top);
-			var mapOffset = p - mapOrigin;
+			var mapOrigin = new CVec(world.Map.Bounds.Left, world.Map.Bounds.Top);
+			var mapOffset = Map.CellToMap(world.Map.TileShape, p) - mapOrigin;
 
 			return new int2(mapRect.X, mapRect.Y) + (previewScale * new float2(mapOffset.X, mapOffset.Y)).ToInt2();
 		}
@@ -253,7 +253,7 @@ namespace OpenRA.Mods.RA.Widgets
 			var viewOrigin = new float2(mapRect.X, mapRect.Y);
 			var mapOrigin = new float2(world.Map.Bounds.Left, world.Map.Bounds.Top);
 			var fcell = mapOrigin + (1f / previewScale) * (p - viewOrigin);
-			return new CPos((int)fcell.X, (int)fcell.Y);
+			return Map.MapToCell(world.Map.TileShape, new CPos((int)fcell.X, (int)fcell.Y));
 		}
 	}
 }
diff --git a/OpenRA.Utility/LegacyMapImporter.cs b/OpenRA.Utility/LegacyMapImporter.cs
index ded0b9d2ab..ce83937535 100644
--- a/OpenRA.Utility/LegacyMapImporter.cs
+++ b/OpenRA.Utility/LegacyMapImporter.cs
@@ -149,8 +149,8 @@ namespace OpenRA.Utility
 
 			map.Smudges = Exts.Lazy(() => new List<SmudgeReference>());
 			map.Actors = Exts.Lazy(() => new Dictionary<string, ActorReference>());
-			map.MapResources = Exts.Lazy(() => new CellLayer<ResourceTile>(size));
-			map.MapTiles = Exts.Lazy(() => new CellLayer<TerrainTile>(size));
+			map.MapResources = Exts.Lazy(() => new CellLayer<ResourceTile>(TileShape.Rectangle, size));
+			map.MapTiles = Exts.Lazy(() => new CellLayer<TerrainTile>(TileShape.Rectangle, size));
 
 			map.Options = new MapOptions();
 
diff --git a/mods/ts/maps/blank-conquest.oramap b/mods/ts/maps/blank-conquest.oramap
deleted file mode 100644
index 512fdbb8fb..0000000000
Binary files a/mods/ts/maps/blank-conquest.oramap and /dev/null differ
diff --git a/mods/ts/maps/blank-testmap/map.bin b/mods/ts/maps/blank-conquest/map.bin
similarity index 96%
rename from mods/ts/maps/blank-testmap/map.bin
rename to mods/ts/maps/blank-conquest/map.bin
index 011a9c1426..1538bf2097 100644
Binary files a/mods/ts/maps/blank-testmap/map.bin and b/mods/ts/maps/blank-conquest/map.bin differ
diff --git a/mods/ts/maps/blank-testmap/map.yaml b/mods/ts/maps/blank-conquest/map.yaml
similarity index 52%
rename from mods/ts/maps/blank-testmap/map.yaml
rename to mods/ts/maps/blank-conquest/map.yaml
index 3cfb223bb1..1f575b9014 100644
--- a/mods/ts/maps/blank-testmap/map.yaml
+++ b/mods/ts/maps/blank-conquest/map.yaml
@@ -4,17 +4,17 @@ MapFormat: 6
 
 RequiresMod: ts
 
-Title: Blank Test Map
+Title: Blank
 
-Description: Test Map
+Description: Placeholder
 
-Author: Reaperrr
+Author: Matthias Mailänder
 
 Tileset: INTERIOR
 
 MapSize: 128,128
 
-Bounds: 16,16,96,96
+Bounds: 32,16,48,96
 
 UseAsShellmap: False
 
@@ -56,53 +56,17 @@ Players:
 
 Actors:
 	Actor0: mpspawn
-		Location: 23,23
+		Location: 50,-24
 		Owner: Neutral
 	Actor1: mpspawn
-		Location: 103,23
+		Location: 126,-24
+		Owner: Neutral
+	Actor2: mpspawn
+		Location: 88,14
+		Owner: Neutral
+	Actor3: mpspawn
+		Location: 88,-62
 		Owner: Neutral
-	Actor2: gatech
-		Location: 90,80
-		Owner: Creeps
-	Actor3: natech
-		Location: 86,80
-		Owner: Creeps
-	Actor4: naradr
-		Location: 82,80
-		Owner: Creeps
-	Actor5: hvr
-		Location: 40,80
-		Owner: Creeps
-	Actor6: cyborg
-		Location: 38,80
-		Owner: Creeps
-	Actor7: cyc2
-		Location: 36,80
-		Owner: Creeps
-	Actor8: bike
-		Location: 34,80
-		Owner: Creeps
-	Actor9: ttnk
-		Location: 32,80
-		Owner: Creeps
-	Actor10: mmch
-		Location: 30,80
-		Owner: Creeps
-	Actor11: gapowr
-		Location: 90,85
-		Owner: Creeps
-	Actor12: gapowr
-		Location: 87,85
-		Owner: Creeps
-	Actor13: napowr
-		Location: 84,85
-		Owner: Creeps
-	Actor14: napowr
-		Location: 81,85
-		Owner: Creeps
-	Actor15: napowr
-		Location: 78,85
-		Owner: Creeps
 
 Smudges:
 
diff --git a/mods/ts/mod.yaml b/mods/ts/mod.yaml
index b9a38c0848..6b9e1eb993 100644
--- a/mods/ts/mod.yaml
+++ b/mods/ts/mod.yaml
@@ -142,6 +142,7 @@ TileSets:
 	mods/ts/tilesets/interior.yaml
 
 TileSize: 48,24
+TileShape: Diamond
 
 Music:
 	mods/ts/music.yaml
diff --git a/mods/ts/sequences/misc.yaml b/mods/ts/sequences/misc.yaml
index 45cf0b5c68..5cf2c51d14 100644
--- a/mods/ts/sequences/misc.yaml
+++ b/mods/ts/sequences/misc.yaml
@@ -1,24 +1,24 @@
 overlay:
-	build-valid-interior: cellsel #TODO remove backfall to RA tileset
-		Start: 3
-	build-valid-snow: cellsel
-		Start: 3
-	build-valid-temperat: cellsel
-		Start: 3
-	build-invalid: cellsel
-		Start: 6
-	target-select: cellsel
-		Start: 10
-	target-valid-desert: cellsel
-		Start: 3
-	target-valid-interior: cellsel
-		Start: 3
-	target-valid-snow: cellsel
-		Start: 3
-	target-valid-temperat: cellsel
-		Start: 3
-	target-invalid: cellsel
-		Start: 6
+	build-valid-interior: place
+		Start: 0
+	build-valid-snow: place
+		Start: 0
+	build-valid-temperat: place
+		Start: 0
+	build-invalid: place
+		Start: 1
+	target-select: place
+		Start: 1
+	target-valid-desert: place
+		Start: 1
+	target-valid-interior: place
+		Start: 1
+	target-valid-snow: place
+		Start: 1
+	target-valid-temperat: place
+		Start: 1
+	target-invalid: place
+		Start: 1
 
 poweroff:
 	offline: poweroff
diff --git a/mods/ts/tilesets/interior.yaml b/mods/ts/tilesets/interior.yaml
index a6ec53d092..f98b79d3ee 100644
--- a/mods/ts/tilesets/interior.yaml
+++ b/mods/ts/tilesets/interior.yaml
@@ -9,7 +9,7 @@ Terrain:
 	TerrainType@Clear:
 		Type: Clear
 		AcceptsSmudgeType: Crater, Scorch
-		Color: 0, 0, 0
+		Color: 116, 85, 55
 		TargetTypes: Ground
 	TerrainType@Tiberium:
 		Type: Tiberium