diff --git a/OemLoader/MainWindow.cs b/OemLoader/MainWindow.cs
new file mode 100644
index 0000000..9f1796d
--- /dev/null
+++ b/OemLoader/MainWindow.cs
@@ -0,0 +1,19 @@
+using Brutal.ImGuiApi;
+
+namespace OemLoader;
+
+public class MainWindow(string title)
+{
+    private readonly ImInputString _filename = new(short.MaxValue);
+    
+    public void Render(double dt)
+    {
+        if (!ProgramPatch.WindowOpen) return;
+        
+        if (ImGui.Begin(title, ref ProgramPatch.WindowOpen))
+        {
+            ImGui.InputTextWithHint("OEM file path", "/home/user/ephemeris.asc", _filename);
+        }
+        ImGui.End();
+    }
+}
\ No newline at end of file
diff --git a/OemLoader/OemLoader.cs b/OemLoader/OemLoader.cs
index 4b4f551..a4641b2 100644
--- a/OemLoader/OemLoader.cs
+++ b/OemLoader/OemLoader.cs
@@ -1,8 +1,8 @@
 using System.Diagnostics;
 using System.Reflection;
+using HarmonyLib;
 using JetBrains.Annotations;
 using KSA;
-using Brutal.ImGuiApi;
 using StarMap.API;
 
 namespace OemLoader;
@@ -12,14 +12,17 @@ namespace OemLoader;
 public class OemLoader
 {
     private readonly string _version;
+    private readonly MainWindow _window;
+    private static Harmony? _harmony = new("OemLoader");
 
     public OemLoader()
     {
-        var version = Assembly.GetExecutingAssembly()
+        var version = typeof(OemLoader).Assembly
             .GetCustomAttribute<AssemblyInformationalVersionAttribute>()?
             .InformationalVersion;
         Debug.Assert(version is not null);
         _version = version;
+        _window = new MainWindow($"OemLoader {_version}");
     }
     
     [UsedImplicitly]
@@ -33,10 +36,21 @@ public class OemLoader
     [StarMapAfterGui]
     public void AfterGui(double dt)
     {
-        if (ImGui.Begin($"OemLoader {_version}"))
-        {
-            ImGui.Text("Hello World!");
-        }
-        ImGui.End();
+        _window.Render(dt);
+    }
+
+    [UsedImplicitly]
+    [StarMapAllModsLoaded]
+    public void FullyLoaded()
+    {
+        _harmony?.PatchAll(typeof(OemLoader).Assembly);
+    }
+
+    [UsedImplicitly]
+    [StarMapUnload]
+    public void Unload()
+    {
+        _harmony?.UnpatchAll("OemLoader");
+        _harmony = null;
     }
 }
\ No newline at end of file
diff --git a/OemLoader/ProgramPatch.cs b/OemLoader/ProgramPatch.cs
new file mode 100644
index 0000000..5514b93
--- /dev/null
+++ b/OemLoader/ProgramPatch.cs
@@ -0,0 +1,41 @@
+using System.Reflection.Emit;
+using HarmonyLib;
+using JetBrains.Annotations;
+using KSA;
+
+namespace OemLoader;
+
+[UsedImplicitly]
+[HarmonyPatch(typeof(Program))]
+internal static class ProgramPatch
+{
+    public static bool WindowOpen;
+
+    private static void DrawMenuItem()
+    {
+        ImGuiHelper.DrawMenuItem("Ephemeris loader", ref WindowOpen);
+    }
+    
+    [UsedImplicitly]
+    [HarmonyPatch(nameof(Program.DrawMenuBar))]
+    [HarmonyTranspiler]
+    private static IEnumerable<CodeInstruction> DrawMenuBarTranspiler(IEnumerable<CodeInstruction> instructions, ILGenerator generator)
+    {
+        // Find the menu item that we want to add ours after
+        var matcher = new CodeMatcher(instructions, generator);
+        matcher.MatchEndForward(
+            CodeMatch.Calls(() => Staging.Toggle()),
+            new CodeMatch(OpCodes.Nop)
+        );
+        matcher.ThrowIfInvalid("Could not find staging menu entry");
+        matcher.Advance(); // the current instruction at this point is just a nop
+        // We want to inject our code before the current instruction, but it should be the target of
+        // the label that was previously on the current instruction, so we need to swap around the labels
+        var labels = new List<Label>(matcher.Instruction.labels);
+        matcher.Instruction.labels.Clear();
+        matcher.Insert(CodeInstruction.Call(() => DrawMenuItem()));
+        matcher.AddLabels(labels);
+        
+        return matcher.InstructionEnumeration();
+    }
+}
\ No newline at end of file