diff --git a/OpenRa.Game/MainWindow.cs b/OpenRa.Game/MainWindow.cs
index e6e04ea724..6f0acbd5af 100755
--- a/OpenRa.Game/MainWindow.cs
+++ b/OpenRa.Game/MainWindow.cs
@@ -48,7 +48,9 @@ namespace OpenRa.Game
 
 			bool windowed = !settings.GetValue("fullscreen", false);
 			renderer = new Renderer(this, GetResolution(settings), windowed);
-			SheetBuilder.Initialize(renderer);
+			SheetBuilder.Initialize(renderer);
+
+			UiOverlay.ShowUnitDebug = settings.GetValue("udebug", false);
 
 			Game.Initialize(settings.GetValue("map", "scg11eb.ini"), renderer, new int2(ClientSize),
 				settings.GetValue("player", 1));
diff --git a/OpenRa.Game/Traits/Mobile.cs b/OpenRa.Game/Traits/Mobile.cs
index 3f64f2e213..f0bb8cfa6f 100644
--- a/OpenRa.Game/Traits/Mobile.cs
+++ b/OpenRa.Game/Traits/Mobile.cs
@@ -125,7 +125,7 @@ namespace OpenRa.Game.Traits
 			float2 from, to;
 			int fromFacing, toFacing;
 
-			Action<Actor, Mobile> OnComplete;
+			Func<Actor, Mobile, bool> OnComplete;
 
 			public MoveTo( int2 destination )
 			{
@@ -185,19 +185,28 @@ namespace OpenRa.Game.Traits
 			}
 
 			void TickMove( Actor self, Mobile mobile )
-			{
+			{
+				var oldFraction = moveFraction;
+				var oldTotal = moveFractionTotal;
+
 				moveFraction += ( self.unitInfo as UnitInfo.MobileInfo ).Speed;
-				UpdateCenterLocation( self, mobile, (float)moveFraction / moveFractionTotal );
+				UpdateCenterLocation( self, mobile );
 				if( moveFraction >= moveFractionTotal )
 				{
-					moveFraction -= moveFractionTotal;
-					OnComplete( self, mobile );
+					moveFraction -= moveFractionTotal;
+					if (!OnComplete(self, mobile))
+					{
+						moveFraction = oldFraction;
+						moveFractionTotal = oldTotal;
+						UpdateCenterLocation(self, mobile );
+					}
 				}
-				return;
 			}
 
-			void UpdateCenterLocation( Actor self, Mobile mobile, float frac )
-			{
+			void UpdateCenterLocation( Actor self, Mobile mobile )
+			{
+				var frac = (float)moveFraction / moveFractionTotal;
+
 				self.CenterLocation = float2.Lerp( from, to, frac );
 				if( moveFraction >= moveFractionTotal )
 					mobile.facing = toFacing & 0xFF;
@@ -221,13 +230,16 @@ namespace OpenRa.Game.Traits
 				return 0.5f * ( CenterOfCell( from ) + CenterOfCell( to ) );
 			}
 
-			void OnCompleteFirstHalf( Actor self, Mobile mobile )
+			bool OnCompleteFirstHalf( Actor self, Mobile mobile )
 			{
 				if( path.Count > 0 )
 				{
 					var nextCell = path[ path.Count - 1 ];
 					if( ( nextCell - mobile.toCell ) != ( mobile.toCell - mobile.fromCell ) )
-					{
+					{
+						if (!CanEnterCell(nextCell, self))
+							return false;
+
 						path.RemoveAt( path.Count - 1 );
 						from = BetweenCells( mobile.fromCell, mobile.toCell );
 						to = BetweenCells( mobile.toCell, nextCell );
@@ -237,8 +249,9 @@ namespace OpenRa.Game.Traits
 						fromFacing = mobile.facing;
 						toFacing = Util.GetNearestFacing( fromFacing, 
 							Util.GetFacing( mobile.toCell-mobile.fromCell, fromFacing ) );
-						OnComplete = OnCompleteFirstHalf;
-						return;
+						OnComplete = OnCompleteFirstHalf;
+						Game.UnitInfluence.Update(mobile);
+						return true;
 					}
 				}
 				from = BetweenCells( mobile.fromCell, mobile.toCell );
@@ -246,15 +259,17 @@ namespace OpenRa.Game.Traits
 				CalculateMoveFraction();
 				fromFacing = toFacing = mobile.facing;
 				OnComplete = OnCompleteSecondHalf;
-				mobile.fromCell = mobile.toCell;
+				mobile.fromCell = mobile.toCell;
+				return true;
 			}
 
-			void OnCompleteSecondHalf( Actor self, Mobile mobile )
+			bool OnCompleteSecondHalf( Actor self, Mobile mobile )
 			{
 				moveFractionTotal = 0;
 				self.CenterLocation = CenterOfCell( mobile.toCell );
 				OnComplete = null;
-				mobile.fromCell = mobile.toCell;
+				mobile.fromCell = mobile.toCell;
+				return true;
 			}
 
 			public void Cancel( Actor self, Mobile mobile )
diff --git a/OpenRa.Game/UiOverlay.cs b/OpenRa.Game/UiOverlay.cs
index 873ae5cfa3..cdb6f784ed 100644
--- a/OpenRa.Game/UiOverlay.cs
+++ b/OpenRa.Game/UiOverlay.cs
@@ -9,15 +9,17 @@ namespace OpenRa.Game
 	class UiOverlay
 	{
 		SpriteRenderer spriteRenderer;
-		Sprite buildOk;
-		Sprite buildBlocked;
+		Sprite buildOk, buildBlocked, unitDebug;
+
+		public static bool ShowUnitDebug = false;
 
 		public UiOverlay(SpriteRenderer spriteRenderer)
 		{
 			this.spriteRenderer = spriteRenderer;
 
 			buildOk = SynthesizeTile(0x80);
-			buildBlocked = SynthesizeTile(0xe6);
+			buildBlocked = SynthesizeTile(0xe6);
+			unitDebug = SynthesizeTile(0x7c);
 		}
 
 		static Sprite SynthesizeTile(byte paletteIndex)
@@ -32,7 +34,13 @@ namespace OpenRa.Game
 		}
 
 		public void Draw()
-		{
+		{
+			if (ShowUnitDebug)
+				for (var j = 0; j < 128; j++)
+					for (var i = 0; i < 128; i++)
+						if (Game.UnitInfluence.GetUnitAt(new int2(i, j)) != null)
+							spriteRenderer.DrawSprite(unitDebug, Game.CellSize * new float2(i, j), 0);
+
 			if (!hasOverlay) return;
 
 			var bi = (UnitInfo.BuildingInfo)Rules.UnitInfo[name];
diff --git a/OpenRa.Game/UnitInfluenceMap.cs b/OpenRa.Game/UnitInfluenceMap.cs
index 64fa602104..438906f569 100644
--- a/OpenRa.Game/UnitInfluenceMap.cs
+++ b/OpenRa.Game/UnitInfluenceMap.cs
@@ -9,7 +9,12 @@ namespace OpenRa.Game
 	class UnitInfluenceMap
 	{
 		Actor[,] influence = new Actor[128, 128];
-		readonly int2 searchDistance = new int2(1, 1);
+		readonly int2 searchDistance = new int2(2,2);
+
+		public UnitInfluenceMap()
+		{
+			Game.world.ActorRemoved += a => Remove(a.traits.GetOrDefault<Mobile>());
+		}
 
 		public void Tick()
 		{
@@ -30,6 +35,8 @@ namespace OpenRa.Game
 
 		public void Remove(Mobile a)
 		{
+			if (a == null) return;
+
 			var min = int2.Max(new int2(0, 0), a.self.Location - searchDistance);
 			var max = int2.Min(new int2(128, 128), a.self.Location + searchDistance);