finished episode 25

src/Main.hs

@@ -119,6 +119,7 @@ main = do
         update sceneObject 0
         render sceneObject
       else do
+        GL.clearColor $= GL.Color4 0 0 0 1
         GL.clear [GL.ColorBuffer]
 
       -- Switch to different scene on keyboard presses F1 thourgh F?
@@ -160,9 +161,15 @@ sceneSwitch curScene evs = mapM_ (switch . SDL.eventPayload) evs
         (SDL.Keysym _ code mod))) =
           when (SDL.toNumber mod == 0) $
             case code of
+              SDL.KeycodeEscape -> do
+                isEmpty <- isEmptyMVar curScene
+                when (not isEmpty) $
+                  void $ tryTakeMVar curScene
               SDL.KeycodeF1 -> do
-                void $ tryTakeMVar curScene
-                putMVar curScene =<< scene1
+                isEmpty <- isEmptyMVar curScene
+                when isEmpty $ do
+                  void $ tryTakeMVar curScene
+                  putMVar curScene =<< scene1
               _             ->
                 return ()
     switch _ = return ()