diff --git a/OpenRa.FileFormats/Map.cs b/OpenRa.FileFormats/Map.cs
index 83d1c811b6..5251dce625 100644
--- a/OpenRa.FileFormats/Map.cs
+++ b/OpenRa.FileFormats/Map.cs
@@ -2,6 +2,7 @@ using System;
 using System.Collections.Generic;
 using System.Text;
 using System.IO;
+using System.Drawing;
 
 namespace OpenRa.FileFormats
 {
@@ -16,6 +17,8 @@ namespace OpenRa.FileFormats
 		public readonly int Width;
 		public readonly int Height;
 
+		public PointF Size { get { return new PointF(Width, Height); } }
+
 		public readonly TileReference[ , ] MapTiles = new TileReference[ 128, 128 ];
 		public readonly List<TreeReference> Trees = new List<TreeReference>();
 
diff --git a/OpenRa.Game/MainWindow.cs b/OpenRa.Game/MainWindow.cs
index 5e7994e2d2..6270438ae6 100644
--- a/OpenRa.Game/MainWindow.cs
+++ b/OpenRa.Game/MainWindow.cs
@@ -76,28 +76,29 @@ namespace OpenRa.Game
 			}
 		}
 
-		Point lastPos;
+		float2 lastPos;
 
 		protected override void OnMouseDown(MouseEventArgs e)
 		{
 			base.OnMouseDown(e);
-			lastPos = e.Location;
+			lastPos = new float2(e.Location);
 		}
 
 		protected override void OnMouseMove(MouseEventArgs e)
 		{
 			base.OnMouseMove(e);
 
-			if (e.Button != 0)
-			{
-				PointF scrollPos = viewport.ScrollPosition;
-				scrollPos.X = Util.Constrain(scrollPos.X + lastPos.X - e.X, new Range<float>(0, map.Width * 24 - ClientSize.Width + 128));
-				scrollPos.Y = Util.Constrain(scrollPos.Y + lastPos.Y - e.Y, new Range<float>(0, map.Height * 24 - ClientSize.Height));
+			if (e.Button == 0)
+				return;
 
-				lastPos = e.Location;
+			float2 scrollPos = new float2(viewport.ScrollPosition) + lastPos - new float2(e.Location);
+			float2 mapSize = 24 * new float2(map.Size) - viewport.Size + new float2(128, 0);
 
-				viewport.ScrollPosition = scrollPos;
-			}
+			scrollPos = scrollPos.Constrain(new Range<float2>(float2.Zero, mapSize));
+
+			lastPos = new float2(e.Location);
+
+			viewport.ScrollPosition = scrollPos.ToPointF();
 		}
 
 		void Frame()
diff --git a/OpenRa.Game/OpenRa.Game.csproj b/OpenRa.Game/OpenRa.Game.csproj
index de5121cc69..406107f042 100644
--- a/OpenRa.Game/OpenRa.Game.csproj
+++ b/OpenRa.Game/OpenRa.Game.csproj
@@ -42,6 +42,7 @@
   <ItemGroup>
     <Compile Include="Actor.cs" />
     <Compile Include="Clock.cs" />
+    <Compile Include="float2.cs" />
     <Compile Include="SheetBuilder.cs" />
     <Compile Include="HardwarePalette.cs" />
     <Compile Include="MainWindow.cs">
diff --git a/OpenRa.Game/Viewport.cs b/OpenRa.Game/Viewport.cs
index 380062a777..99e4091f0d 100644
--- a/OpenRa.Game/Viewport.cs
+++ b/OpenRa.Game/Viewport.cs
@@ -21,10 +21,11 @@ namespace OpenRa.Game
 			get { return clientSize; }
 		} 
 
-
 		public Viewport(Size clientSize)
 		{
 			this.clientSize = clientSize;
 		}
+
+		public float2 Size { get { return new float2(clientSize); } }
 	}
 }
diff --git a/OpenRa.Game/float2.cs b/OpenRa.Game/float2.cs
new file mode 100644
index 0000000000..ffa9b8921d
--- /dev/null
+++ b/OpenRa.Game/float2.cs
@@ -0,0 +1,74 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using System.Runtime.InteropServices;
+using System.Drawing;
+using BluntDirectX.Direct3D;
+
+namespace OpenRa.Game
+{
+	[StructLayout(LayoutKind.Sequential)]
+	class float2
+	{
+		public float X, Y;
+
+		public float2(float x, float y)
+		{
+			X = x;
+			Y = y;
+		}
+
+		public PointF ToPointF()
+		{
+			return new PointF(X, Y);
+		}
+
+		public float2(PointF p)
+		{
+			X = p.X;
+			Y = p.Y;
+		}
+
+		public float2(Point p)
+		{
+			X = p.X;
+			Y = p.Y;
+		}
+
+		public float2(Size p)
+		{
+			X = p.Width;
+			Y = p.Height;
+		}
+
+		public float2(SizeF p)
+		{
+			X = p.Width;
+			Y = p.Height;
+		}
+
+		public static float2 operator +(float2 a, float2 b)
+		{
+			return new float2(a.X + b.X, a.Y + b.Y);
+		}
+
+		public static float2 operator -(float2 a, float2 b)
+		{
+			return new float2(a.X - b.X, a.Y - b.Y);
+		}
+
+		public float2 Constrain(Range<float2> r)
+		{
+			return new float2(
+				Util.Constrain(X, new Range<float>(r.Start.X, r.End.X)),
+				Util.Constrain(Y, new Range<float>(r.Start.Y, r.End.Y)));
+		}
+
+		public static float2 operator *(float a, float2 b)
+		{
+			return new float2(a * b.X, a * b.Y);
+		}
+
+		public static readonly float2 Zero = new float2(0, 0);
+	}
+}