diff --git a/gluturtle.cabal b/gluturtle.cabal
--- a/gluturtle.cabal
+++ b/gluturtle.cabal
@@ -2,7 +2,7 @@
 cabal-version:	>= 1.6
 
 name:		gluturtle
-version:	0.0.23
+version:	0.0.26
 stability:	alpha
 author:		Yoshikuni Jujo <PAF01143@nifty.ne.jp>
 maintainer:	Yoshikuni Jujo <PAF01143@nifty.ne.jp>
diff --git a/src/Graphics/UI/GLUT/Turtle/Field.hs b/src/Graphics/UI/GLUT/Turtle/Field.hs
--- a/src/Graphics/UI/GLUT/Turtle/Field.hs
+++ b/src/Graphics/UI/GLUT/Turtle/Field.hs
@@ -4,7 +4,7 @@
 	initialize,
 
 	-- * types and classes
-	Field,
+	Field(fRunning),
 	Layer,
 	Character,
 	Coordinates(..),
@@ -115,7 +115,10 @@
 
 	fPrompt :: IORef String,
 
-	fLayers :: IORef Layers
+	fLayers :: IORef Layers,
+
+	fRunning :: IORef Bool,
+	fBusy :: IORef Bool
  }
 
 addLayer :: Field -> IO Layer
@@ -136,6 +139,8 @@
 
 openField :: String -> Int -> Int -> IO Field
 openField name w h = do
+	fb <- newIORef False
+	fr <- newIORef False
 	fw <- newIORef w
 	fh <- newIORef h
 	layers <- newLayers 0 (return ()) (return ()) (return ())
@@ -152,11 +157,7 @@
 	initialWindowSize $= Size (fromIntegral w) (fromIntegral h)
 	wt <- createWindow name
 	wc <- createWindow "console"
-	currentWindow $= Just wt
-	displayCallback $= (sequence_ . catMaybes =<< readIORef actions)
-	currentWindow $= Just wc
-	displayCallback $= (sequence_ . catMaybes =<< readIORef actions)
-	G.addTimerCallback 10 (timerAction $ do
+	let act = do
 		currentWindow $= Just wt
 		G.clearColor $= G.Color4 0 0 0 0
 		G.clear [G.ColorBuffer]
@@ -171,7 +172,13 @@
 		ss1 <- readIORef str
 		ss2 <- readIORef str2
 		zipWithM_ (printString (-2.8)) [-1800, -1600 .. 1800] (reverse ss1 ++ ss2)
-		swapBuffers)
+		swapBuffers
+	currentWindow $= Just wt
+	displayCallback $= act
+	currentWindow $= Just wc
+	displayCallback $= act
+--	G.keyboardMouseCallback $= Just (\_ _ _ _ -> act)
+--	G.addTimerCallback 10 $ timerAction act
 	G.reshapeCallback $= Just (\size -> G.viewport $= (G.Position 0 0, size))
 	let f = Field{
 		fCoordinates = CoordCenter,
@@ -187,9 +194,20 @@
 		fConsoleWindow = wc,
 		fPrompt = prmpt,
 
-		fBgcolor = bgc
+		fBgcolor = bgc,
+
+		fBusy = fb,
+		fRunning = fr
 	 }
-	G.keyboardMouseCallback $= Just (keyboardProc f)
+	G.keyboardMouseCallback $= Just (\k ks m p -> do
+		keyboardProc f k ks m p
+		act
+		busy <- readIORef $ fBusy f
+		when (k == G.Char '\r' && not busy) $ do
+			writeIORef (fBusy f) True
+			G.addTimerCallback 10 $ timerActionN f 10 act)
+--	G.keyboardMouseCallback $= Just (\_ _ _ _ -> act)
+--	G.addTimerCallback 10 $ timerAction act
 	return f
 
 printString :: GLfloat -> GLfloat -> String -> IO ()
@@ -207,6 +225,15 @@
 timerAction act = do
 	_ <- act
 	G.addTimerCallback 10 $ timerAction act
+
+timerActionN :: Field -> Int -> IO a -> IO ()
+-- timerActionN f 0 _ = writeIORef (fBusy f) False
+timerActionN f n act = do
+	b <- readIORef $ fRunning f
+	if b then act >> G.addTimerCallback 10 (timerActionN f undefined act)
+		else act >> writeIORef (fBusy f) False
+--	_ <- act
+--	G.addTimerCallback 10 $ timerActionN f (n - 1) act
 
 -- data InputType = XInput | End | Timer
 
diff --git a/src/Graphics/UI/GLUT/Turtle/Move.hs b/src/Graphics/UI/GLUT/Turtle/Move.hs
--- a/src/Graphics/UI/GLUT/Turtle/Move.hs
+++ b/src/Graphics/UI/GLUT/Turtle/Move.hs
@@ -40,7 +40,7 @@
 
 import Graphics.UI.GLUT.Turtle.State(TurtleState(..), makeShape)
 import Graphics.UI.GLUT.Turtle.Field(prompt, initialize, setFieldSize,
-	Field, Layer, Character, Coordinates(..),
+	Field(fRunning), Layer, Character, Coordinates(..),
 	openField, closeField, waitField, coordinates, topleft, center,
 	fieldSize, forkField, flushField, clearLayer,
 	clearCharacter, addLayer, addCharacter,
@@ -55,6 +55,8 @@
 import Control.Monad(when, unless, forM_)
 import Data.Maybe(isJust)
 
+import Data.IORef
+
 --------------------------------------------------------------------------------
 
 moveTurtle :: Field -> Character -> Layer -> TurtleState -> TurtleState -> IO ()
@@ -68,11 +70,13 @@
 			undoField f
 			when (visible t1) $ drawTtl (direction t0) $ position t0
 	when (visible t1) $ do
+		writeIORef (fRunning f) True
 		forM_ (directions t0 t1) $ \dir -> fl $
 			drawTtl dir (position t0) >> threadDelay (interval t0)
 		forM_ (positions w h t0 t1) $ \p -> fl $
 			drawTtl (direction t1) p >> threadDelay (interval t0)
 		fl $ drawTtl (direction t1) $ position t1
+		writeIORef (fRunning f) False
 	when (visible t0 && not (visible t1)) $ fl $ clearCharacter f
 	when (clear t1) $ fl $ clearLayer l
 	unless (undo t1) $ fl $ maybe (return ()) (drawSVG f l) (draw t1)