diff --git a/OpenRa.TechTreeTest/Building.cs b/OpenRa.TechTreeTest/Building.cs
new file mode 100644
index 0000000000..2fe40ed1d3
--- /dev/null
+++ b/OpenRa.TechTreeTest/Building.cs
@@ -0,0 +1,66 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace OpenRa.TechTreeTest
+{
+	class Building
+	{
+		readonly string friendlyName;
+
+		public string FriendlyName
+		{
+			get { return friendlyName; }
+		}
+
+		string[] prerequisites;
+
+		public string[] Prerequisites
+		{
+			get { return prerequisites; }
+			set { prerequisites = value; }
+		}
+
+		int techLevel;
+
+		public int TechLevel
+		{
+			get { return techLevel; }
+			set { techLevel = value; }
+		}
+
+		public Building(string friendlyName)
+		{
+			this.friendlyName = friendlyName;
+		}
+
+		public bool ShouldMakeBuildable(IEnumerable<string> buildings)
+		{
+			List<string> p = new List<string>(prerequisites);
+			foreach (string b in buildings)
+				p.Remove(b);
+
+			return p.Count == 0;
+		}
+
+		public bool ShouldMakeUnbuildable(IEnumerable<string> buildings)
+		{
+			List<string> p = new List<string>(prerequisites);
+			foreach (string b in buildings)
+				p.Remove(b);
+
+			return p.Count == prerequisites.Length;
+		}
+
+		bool buildable = false;
+		public bool Buildable { get { return buildable; } }
+
+		public void CheckPrerequisites(IEnumerable<string> buildings)
+		{
+			if (buildable && ShouldMakeUnbuildable(buildings))
+				buildable = false;
+			else if (!buildable && ShouldMakeBuildable(buildings))
+				buildable = true;
+		}
+	}
+}
diff --git a/OpenRa.TechTreeTest/Form1.cs b/OpenRa.TechTreeTest/Form1.cs
index 9602c31201..6a5d019eca 100644
--- a/OpenRa.TechTreeTest/Form1.cs
+++ b/OpenRa.TechTreeTest/Form1.cs
@@ -10,6 +10,7 @@ namespace OpenRa.TechTreeTest
 {
 	public partial class Form1 : Form
 	{
+		TechTree techTree;
 		public Form1()
 		{
 			InitializeComponent();
diff --git a/OpenRa.TechTreeTest/TechTree.cs b/OpenRa.TechTreeTest/TechTree.cs
index 85504056c1..8d9988efe5 100644
--- a/OpenRa.TechTreeTest/TechTree.cs
+++ b/OpenRa.TechTreeTest/TechTree.cs
@@ -10,6 +10,7 @@ namespace OpenRa.TechTreeTest
 	class TechTree
 	{
 		Dictionary<string, Building> buildings = new Dictionary<string,Building>();
+		List<string> built;
 		public TechTree()
 		{
 			LoadBuildings();
@@ -40,65 +41,31 @@ namespace OpenRa.TechTreeTest
 				buildings.Add(m.Groups[0].Value, new Building(m.Groups[1].Value));
 			}
 		}
-	}
 
-	class Building
-	{
-		readonly string friendlyName;
-
-		public string FriendlyName
+		public bool Build(string key)
 		{
-			get { return friendlyName; }
-		} 
-
-		string[] prerequisites;
-
-		public string[] Prerequisites
-		{
-			get { return prerequisites; }
-			set { prerequisites = value; }
+			Building b = buildings[key];
+			if (!b.Buildable) return false;
+			built.Add(key);
+			CheckAll();
+			return true;
 		}
 
-		int techLevel;
-
-		public int TechLevel
+		public bool Unbuild(string key)
 		{
-			get { return techLevel; }
-			set { techLevel = value; }
+			Building b = buildings[key];
+			if (!built.Contains(key)) return false;
+			built.Remove(key);
+			CheckAll();
+			return true;
 		}
 
-		public Building(string friendlyName)
+		void CheckAll()
 		{
-			this.friendlyName = friendlyName;
-		}
-
-		public bool ShouldMakeBuildable(IEnumerable<string> buildings)
-		{
-			List<string> p = new List<string>(prerequisites);
-			foreach (string b in buildings)
-				p.Remove(b);
-
-			return p.Count == 0;
-		}
-
-		public bool ShouldMakeUnbuildable(IEnumerable<string> buildings)
-		{
-			List<string> p = new List<string>(prerequisites);
-			foreach (string b in buildings)
-				p.Remove(b);
-
-			return p.Count == prerequisites.Length;
-		}
-
-		bool buildable = false;
-		public bool Buildable { get { return buildable; } }
-
-		public void CheckPrerequisites(IEnumerable<string> buildings)
-		{
-			if (buildable && ShouldMakeUnbuildable(buildings))
-				buildable = false;
-			else if (!buildable && ShouldMakeBuildable(buildings))
-				buildable = true;
+			foreach (Building building in buildings.Values)
+			{
+				building.CheckPrerequisites(built);
+			}
 		}
 	}
 }