diff --git a/example/main.go b/example/main.go
index 0d85a49ec..3197f7c63 100644
--- a/example/main.go
+++ b/example/main.go
@@ -9,9 +9,7 @@ import (
 	"github.com/hajimehoshi/go-ebiten/example/game/rotating"
 	"github.com/hajimehoshi/go-ebiten/example/game/sprites"
 	"github.com/hajimehoshi/go-ebiten/example/game/testpattern"
-	"github.com/hajimehoshi/go-ebiten/ui"
 	"github.com/hajimehoshi/go-ebiten/ui/cocoa"
-	// "github.com/hajimehoshi/go-ebiten/ui/glut"
 	"os"
 	"runtime"
 )
@@ -23,10 +21,6 @@ func main() {
 	if 2 <= len(os.Args) {
 		gameName = os.Args[1]
 	}
-	uiName := "cocoa"
-	if 3 <= len(os.Args) {
-		uiName = os.Args[2]
-	}
 
 	var game ebiten.Game
 	switch gameName {
@@ -52,12 +46,11 @@ func main() {
 	const screenHeight = 240
 	const screenScale = 2
 	const title = "Ebiten Demo"
-	var u ui.UI
-	switch uiName {
-	default:
-		fallthrough
-	case "cocoa":
-		u = cocoa.New(screenWidth, screenHeight, screenScale, title)
+	ui := cocoa.New(screenWidth, screenHeight, screenScale, title)
+	ui.Start(game)
+	ui.InitTextures(game)
+	for {
+		ui.WaitEvents()
+		ui.Draw(game.Draw)
 	}
-	u.Run(game)
 }
diff --git a/graphics/opengl/device.go b/graphics/opengl/device.go
index 0380001ac..841c581e1 100644
--- a/graphics/opengl/device.go
+++ b/graphics/opengl/device.go
@@ -6,13 +6,13 @@ import (
 )
 
 type Device struct {
-	context     *Context
+	context *Context
 }
 
 func NewDevice(screenWidth, screenHeight, screenScale int) *Device {
-	graphicsContext := newContext(screenWidth, screenHeight, screenScale)
+	context := newContext(screenWidth, screenHeight, screenScale)
 	return &Device{
-		context:     graphicsContext,
+		context: context,
 	}
 }
 
diff --git a/ui/cocoa/cocoa.go b/ui/cocoa/cocoa.go
index db94c92aa..42cb244cc 100644
--- a/ui/cocoa/cocoa.go
+++ b/ui/cocoa/cocoa.go
@@ -1,20 +1,24 @@
 package cocoa
 
-// #cgo CFLAGS: -x objective-c -fobjc-arc
+// #cgo CFLAGS: -x objective-c
 // #cgo LDFLAGS: -framework Cocoa -framework OpenGL -framework QuartzCore
-//
+// 
 // #include <stdlib.h>
 // #include "input.h"
 //
-// void Run(size_t width, size_t height, size_t scale, const char* title);
+// void Start(size_t width, size_t height, size_t scale, const char* title);
+// void WaitEvents(void);
+// void BeginDrawing(void);
+// void EndDrawing(void);
 //
 import "C"
 import (
 	"github.com/hajimehoshi/go-ebiten"
+	"github.com/hajimehoshi/go-ebiten/graphics"
 	"github.com/hajimehoshi/go-ebiten/graphics/opengl"
+	"runtime"
 	"sync"
 	"time"
-	"runtime"
 	"unsafe"
 )
 
@@ -41,16 +45,16 @@ func (context *GameContext) InputState() ebiten.InputState {
 }
 
 type UI struct {
-	screenWidth               int
-	screenHeight              int
-	screenScale               int
-	title                     string
-	updating                  chan ebiten.Game
-	updated                   chan ebiten.Game
-	input                     chan ebiten.InputState
-	graphicsDevice            *opengl.Device
-	funcsExecutedOnMainThread []func() // TODO: map?
-	lock                      sync.Mutex
+	screenWidth       int
+	screenHeight      int
+	screenScale       int
+	title             string
+	updating          chan struct{}
+	updated           chan struct{}
+	input             chan ebiten.InputState
+	graphicsDevice    *opengl.Device
+	lock              sync.Mutex
+	gameContext       *GameContext
 }
 
 var currentUI *UI
@@ -60,14 +64,18 @@ func New(screenWidth, screenHeight, screenScale int, title string) *UI {
 		panic("UI can't be duplicated.")
 	}
 	ui := &UI{
-		screenWidth:  screenWidth,
-		screenHeight: screenHeight,
-		screenScale:  screenScale,
-		title:        title,
-		updating:     make(chan ebiten.Game),
-		updated:      make(chan ebiten.Game),
-		input:        make(chan ebiten.InputState),
-		funcsExecutedOnMainThread: []func(){},
+		screenWidth:       screenWidth,
+		screenHeight:      screenHeight,
+		screenScale:       screenScale,
+		title:             title,
+		updating:          make(chan struct{}),
+		updated:           make(chan struct{}),
+		input:             make(chan ebiten.InputState),
+		gameContext: &GameContext{
+			screenWidth:  screenWidth,
+			screenHeight: screenHeight,
+			inputState:   ebiten.InputState{-1, -1},
+		},
 	}
 	currentUI = ui
 	return ui
@@ -76,50 +84,45 @@ func New(screenWidth, screenHeight, screenScale int, title string) *UI {
 func (ui *UI) gameMainLoop(game ebiten.Game) {
 	frameTime := time.Duration(int64(time.Second) / int64(ebiten.FPS))
 	tick := time.Tick(frameTime)
-	gameContext := &GameContext{
-		screenWidth:  ui.screenWidth,
-		screenHeight: ui.screenHeight,
-		inputState:   ebiten.InputState{-1, -1},
-	}
-	ui.InitializeGame(game)
 	for {
 		select {
-		case gameContext.inputState = <-ui.input:
+		case ui.gameContext.inputState = <-ui.input:
 		case <-tick:
-			game.Update(gameContext)
-		case ui.updating <- game:
-			game = <-ui.updated
+			game.Update(ui.gameContext)
+		case ui.updating <- struct{}{}:
+			//ui.DrawGame(game)
+			<-ui.updated
 		}
 	}
 }
 
-func (ui *UI) Run(game ebiten.Game) {
+func (ui *UI) Start(game ebiten.Game) {
 	go ui.gameMainLoop(game)
-	runtime.LockOSThread()
 
 	cTitle := C.CString(ui.title)
 	defer C.free(unsafe.Pointer(cTitle))
 
-	C.Run(C.size_t(ui.screenWidth),
+	C.Start(C.size_t(ui.screenWidth),
 		C.size_t(ui.screenHeight),
 		C.size_t(ui.screenScale),
 		cTitle)
+	C.WaitEvents()
 }
 
-func (ui *UI) InitializeGame(game ebiten.Game) {
-	ui.lock.Lock()
-	defer ui.lock.Unlock()
-	ui.funcsExecutedOnMainThread = append(ui.funcsExecutedOnMainThread, func() {
-		game.InitTextures(ui.graphicsDevice.TextureFactory())
-	})
+func (ui *UI) WaitEvents() {
+	C.WaitEvents()
 }
 
-func (ui *UI) DrawGame(game ebiten.Game) {
-	ui.lock.Lock()
-	defer ui.lock.Unlock()
-	ui.funcsExecutedOnMainThread = append(ui.funcsExecutedOnMainThread, func() {
-		ui.graphicsDevice.Update(game.Draw)
-	})
+func (ui *UI) InitTextures(game ebiten.Game) {
+	C.BeginDrawing()
+	game.InitTextures(ui.graphicsDevice.TextureFactory())
+	C.EndDrawing()
+}
+
+func (ui *UI) Draw(f func(graphics.Context)) {
+	C.BeginDrawing()
+	ui.graphicsDevice.Update(f)
+	C.EndDrawing()
 }
 
 //export ebiten_EbitenOpenGLView_Initialized
@@ -127,7 +130,6 @@ func ebiten_EbitenOpenGLView_Initialized() {
 	if currentUI.graphicsDevice != nil {
 		panic("The graphics device is already initialized")
 	}
-
 	currentUI.graphicsDevice = opengl.NewDevice(
 		currentUI.screenWidth,
 		currentUI.screenHeight,
@@ -136,16 +138,6 @@ func ebiten_EbitenOpenGLView_Initialized() {
 
 //export ebiten_EbitenOpenGLView_Updating
 func ebiten_EbitenOpenGLView_Updating() {
-	currentUI.lock.Lock()
-	defer currentUI.lock.Unlock()
-	for _, f := range currentUI.funcsExecutedOnMainThread {
-		f()
-	}
-	currentUI.funcsExecutedOnMainThread = currentUI.funcsExecutedOnMainThread[0:0]
-
-	game := <-currentUI.updating
-	currentUI.graphicsDevice.Update(game.Draw)
-	currentUI.updated <- game
 }
 
 //export ebiten_EbitenOpenGLView_InputUpdated
diff --git a/ui/cocoa/ebiten_opengl_view.c b/ui/cocoa/ebiten_opengl_view.c
index 0a280a38b..801313639 100644
--- a/ui/cocoa/ebiten_opengl_view.c
+++ b/ui/cocoa/ebiten_opengl_view.c
@@ -13,7 +13,7 @@ void ebiten_EbitenOpenGLView_InputUpdated(InputType inputType, int x, int y);
 
 // TODO: Use NSViewController?
 
-static CVReturn
+/*static CVReturn
 EbitenDisplayLinkCallback(CVDisplayLinkRef displayLink,
                           CVTimeStamp const* now,
                           CVTimeStamp const* outputTime,
@@ -28,19 +28,26 @@ EbitenDisplayLinkCallback(CVDisplayLinkRef displayLink,
     EbitenOpenGLView* view = (__bridge EbitenOpenGLView*)displayLinkContext;
     return [view getFrameForTime:outputTime];
   }
-}
+  }*/
 
 @implementation EbitenOpenGLView {
-@private
-  CVDisplayLinkRef displayLink_;
+  /*@private
+    CVDisplayLinkRef displayLink_;*/
 }
 
-- (void)dealloc {
+/*- (void)dealloc {
   CVDisplayLinkRelease(self->displayLink_);
-  // Do not call [super dealloc] because of ARC.
-}
+#if !__has_feature(objc_arc)
+  [super dealloc];
+#endif
+}*/
 
-- (void)prepareOpenGL {
+/*- (void)prepareOpenGL {
+  [super prepareOpenGL];
+  ebiten_EbitenOpenGLView_Initialized();
+  }*/
+
+/*- (void)prepareOpenGL {
   [super prepareOpenGL];
   NSOpenGLContext* openGLContext = [self openGLContext];
   assert(openGLContext != nil);
@@ -60,9 +67,9 @@ EbitenDisplayLinkCallback(CVDisplayLinkRef displayLink,
   CVDisplayLinkStart(self->displayLink_);
 
   ebiten_EbitenOpenGLView_Initialized();
-}
+  }*/
 
-- (CVReturn)getFrameForTime:(CVTimeStamp const*)outputTime {
+/*- (CVReturn)getFrameForTime:(CVTimeStamp const*)outputTime {
   (void)outputTime;
   NSOpenGLContext* context = [self openGLContext];
   assert(context != nil);
@@ -74,7 +81,7 @@ EbitenDisplayLinkCallback(CVDisplayLinkRef displayLink,
     CGLUnlockContext((CGLContextObj)[context CGLContextObj]);
   }
   return kCVReturnSuccess;
-}
+  }*/
 
 - (BOOL)isFlipped {
   return YES;
diff --git a/ui/cocoa/ebiten_opengl_view.h b/ui/cocoa/ebiten_opengl_view.h
index 802065c0a..d395bdcfd 100644
--- a/ui/cocoa/ebiten_opengl_view.h
+++ b/ui/cocoa/ebiten_opengl_view.h
@@ -8,7 +8,7 @@
 
 @interface EbitenOpenGLView : NSOpenGLView
 
-- (CVReturn)getFrameForTime:(CVTimeStamp const*)outputTime;
+//- (CVReturn)getFrameForTime:(CVTimeStamp const*)outputTime;
 
 @end
 
diff --git a/ui/cocoa/ebiten_window.c b/ui/cocoa/ebiten_window.c
index 58f845270..2fbac108a 100644
--- a/ui/cocoa/ebiten_window.c
+++ b/ui/cocoa/ebiten_window.c
@@ -2,9 +2,16 @@
 
 #import "ebiten_window.h"
 
+#include <OpenGL/gl.h>
+
 #import "ebiten_opengl_view.h"
 
+void ebiten_EbitenOpenGLView_Initialized(void);
+
 @implementation EbitenWindow
+{
+  NSOpenGLContext* glContext_;
+}
 
 - (id)initWithSize:(NSSize)size {
   NSUInteger style = (NSTitledWindowMask | NSClosableWindowMask |
@@ -31,6 +38,20 @@
   [self setDocumentEdited:YES];
 
   NSRect rect = NSMakeRect(0, 0, size.width, size.height);
+  NSView* contentView = [[NSView alloc] initWithFrame:rect];
+  [self setContentView:contentView];
+
+  return self;
+
+  /*EbitenOpenGLView* contentView =
+    [[EbitenOpenGLView alloc] initWithFrame:rect
+    pixelFormat:format];*/
+}
+
+- (NSOpenGLContext*)glContext {
+  if (self->glContext_ != nil)
+    return self->glContext_;
+
   NSOpenGLPixelFormatAttribute attributes[] = {
     NSOpenGLPFAWindow,
     NSOpenGLPFADoubleBuffer,
@@ -40,11 +61,15 @@
   };
   NSOpenGLPixelFormat* format = [[NSOpenGLPixelFormat alloc]
                                   initWithAttributes:attributes];
-  EbitenOpenGLView* glView =
-    [[EbitenOpenGLView alloc] initWithFrame:rect
-                                pixelFormat:format];
-  [self setContentView:glView];
-  return self;
+  self->glContext_ = [[NSOpenGLContext alloc] initWithFormat:format
+                                                shareContext:nil];
+  [self->glContext_ setView:[self contentView]];
+  [self->glContext_ makeCurrentContext];
+  ebiten_EbitenOpenGLView_Initialized();
+
+  [format release];
+
+  return self->glContext_;
 }
 
 - (BOOL)windowShouldClose:(id)sender {
@@ -60,6 +85,7 @@
                       modalDelegate:self
                      didEndSelector:selector
                         contextInfo:nil];
+    [alert release];
   }
   return NO;
 }
@@ -74,5 +100,13 @@
   }
 }
 
-@end
+- (void)beginDrawing {
+  [[self glContext] makeCurrentContext];
+  glClear(GL_COLOR_BUFFER_BIT);
+}
 
+- (void)endDrawing {
+  [[self glContext] flushBuffer];
+}
+
+@end
diff --git a/ui/cocoa/ebiten_window.h b/ui/cocoa/ebiten_window.h
index 1c69bf49e..b5bc4f961 100644
--- a/ui/cocoa/ebiten_window.h
+++ b/ui/cocoa/ebiten_window.h
@@ -12,6 +12,8 @@
          returnCode:(NSInteger)returnCode
         contextInfo:(void*)contextInfo;
 - (BOOL)windowShouldClose:(id)sender;
+- (void)beginDrawing;
+- (void)endDrawing;
 
 @end
 
diff --git a/ui/cocoa/mainloop.c b/ui/cocoa/mainloop.c
new file mode 100644
index 000000000..6b55efd0b
--- /dev/null
+++ b/ui/cocoa/mainloop.c
@@ -0,0 +1,45 @@
+// -*- objc -*-
+
+#include <stdlib.h>
+
+#import "ebiten_controller.h"
+#import "ebiten_window.h"
+
+static EbitenWindow* currentWindow = 0;
+
+void Start(size_t width, size_t height, size_t scale, const char* title) {
+  NSSize size = NSMakeSize(width * scale, height * scale);
+  EbitenWindow* window = [[EbitenWindow alloc]
+                            initWithSize:size];
+  [window setTitle: [[NSString alloc] initWithUTF8String:title]];  
+  EbitenController* controller = [[EbitenController alloc]
+                                    initWithWindow:window];
+  NSApplication* app = [NSApplication sharedApplication];
+  [app setActivationPolicy:NSApplicationActivationPolicyRegular];
+  [app setDelegate:controller];
+  [app finishLaunching];
+  [app activateIgnoringOtherApps:YES];
+
+  currentWindow = window;
+}
+
+void WaitEvents(void) {
+  for (;;) {
+    NSEvent* event = [NSApp nextEventMatchingMask:NSAnyEventMask
+                                        untilDate:[NSDate distantPast]
+                                           inMode:NSDefaultRunLoopMode
+                                          dequeue:YES];
+    if (event == nil) {
+      break;
+    }
+    [NSApp sendEvent:event];
+  }
+}
+
+void BeginDrawing(void) {
+  [currentWindow beginDrawing];
+}
+
+void EndDrawing(void) {
+  [currentWindow endDrawing];
+}
diff --git a/ui/cocoa/run.c b/ui/cocoa/run.c
deleted file mode 100644
index fc687888a..000000000
--- a/ui/cocoa/run.c
+++ /dev/null
@@ -1,23 +0,0 @@
-// -*- objc -*-
-
-#include <stdlib.h>
-
-#import "ebiten_controller.h"
-#import "ebiten_window.h"
-
-void Run(size_t width, size_t height, size_t scale, const char* title) {
-  @autoreleasepool {
-    NSSize size = NSMakeSize(width * scale, height * scale);
-    EbitenWindow* window = [[EbitenWindow alloc]
-                            initWithSize:size];
-    [window setTitle: [[NSString alloc] initWithUTF8String:title]];  
-    EbitenController* controller = [[EbitenController alloc]
-                                    initWithWindow:window];
-    NSApplication* app = [NSApplication sharedApplication];
-    [app setActivationPolicy:NSApplicationActivationPolicyRegular];
-    [app setDelegate:controller];
-    [app finishLaunching];
-    [app activateIgnoringOtherApps:YES];
-    [app run];
-  }
-}
diff --git a/ui/ui.go b/ui/ui.go
index 161537aed..5b1faa293 100644
--- a/ui/ui.go
+++ b/ui/ui.go
@@ -1,9 +1 @@
 package ui
-
-import (
-	"github.com/hajimehoshi/go-ebiten"
-)
-
-type UI interface {
-	Run(game ebiten.Game)
-}