diff --git a/OpenRa.Game/Graphics/Animation.cs b/OpenRa.Game/Graphics/Animation.cs
index b7fd3d913c..00fa963dc2 100644
--- a/OpenRa.Game/Graphics/Animation.cs
+++ b/OpenRa.Game/Graphics/Animation.cs
@@ -7,6 +7,7 @@ namespace OpenRa.Game.Graphics
 		readonly string name;
 		Sequence currentSequence;
 		int frame = 0;
+		bool backwards = false;
 		bool tickAlways;
 
 		public Animation( string name )
@@ -15,7 +16,16 @@ namespace OpenRa.Game.Graphics
 			Play( "idle" );
 		}
 
-		public Sprite Image { get { return currentSequence.GetSprite( frame ); } }
+		public Sprite Image
+		{
+			get
+			{
+				return backwards
+					? currentSequence.GetSprite(currentSequence.End - frame - 1)
+					: currentSequence.GetSprite(frame);
+			}
+		}
+
 		public float2 Center { get { return 0.25f * new float2(currentSequence.GetSprite(0).bounds.Size); } }
 
 		public void Play( string sequenceName )
@@ -23,6 +33,11 @@ namespace OpenRa.Game.Graphics
 			PlayThen(sequenceName, () => { });
 		}
 
+		public void PlayBackwards(string sequenceName)
+		{
+			PlayBackwardsThen(sequenceName, () => { });
+		}
+
 		public void PlayRepeating( string sequenceName )
 		{
 			PlayThen( sequenceName, () => PlayRepeating( sequenceName ) );
@@ -30,6 +45,7 @@ namespace OpenRa.Game.Graphics
 
 		public void PlayThen( string sequenceName, Action after )
 		{
+			backwards = false;
 			tickAlways = false;
 			currentSequence = SequenceProvider.GetSequence( name, sequenceName );
 			frame = 0;
@@ -45,8 +61,15 @@ namespace OpenRa.Game.Graphics
 			};
 		}
 
+		public void PlayBackwardsThen(string sequenceName, Action after)
+		{
+			PlayThen(sequenceName, after);
+			backwards = true;
+		}
+
 		public void PlayFetchIndex( string sequenceName, Func<int> func )
 		{
+			backwards = false;
 			tickAlways = true;
 			currentSequence = SequenceProvider.GetSequence( name, sequenceName );
 			frame = func();
diff --git a/OpenRa.Game/Traits/RenderBuildingWarFactory.cs b/OpenRa.Game/Traits/RenderBuildingWarFactory.cs
index ec56359911..c4b13a8a3f 100644
--- a/OpenRa.Game/Traits/RenderBuildingWarFactory.cs
+++ b/OpenRa.Game/Traits/RenderBuildingWarFactory.cs
@@ -11,6 +11,7 @@ namespace OpenRa.Game.Traits
 	{
 		public Animation roof;
 		bool doneBuilding;
+		bool isOpen;
 		public readonly Actor self;
 
 		public RenderWarFactory(Actor self)
@@ -37,14 +38,22 @@ namespace OpenRa.Game.Traits
 		{
 			base.Tick(self);
 			roof.Tick();
+
+			var b = self.Bounds;
+			if (isOpen && !Game.SelectUnitsInBox(
+				new float2(b.Left, b.Top),
+				new float2(b.Right, b.Bottom)).Any(a => a.traits.Contains<Mobile>()))
+			{
+				isOpen = false;
+				roof.PlayBackwardsThen("build-top", () => roof.Play("idle-top"));
+			}
 		}
 
 		public void EjectUnit()
 		{
 			/* todo: hold the door open */
 
-			roof.PlayThen("build-top", 
-				() => roof.PlayRepeating("idle-top"));
+			roof.PlayThen("build-top", () => isOpen = true);
 		}
 	}
 }