diff --git a/example/main.go b/example/main.go
index 0ea6bae42..1ff15c229 100644
--- a/example/main.go
+++ b/example/main.go
@@ -28,7 +28,7 @@ func main() {
 
 	u := cocoa.UI()
 	textureFactory := cocoa.TextureFactory()
-	window := u.CreateWindow(screenWidth, screenHeight, screenScale, title)
+	window := u.CreateGameWindow(screenWidth, screenHeight, screenScale, title)
 
 	textureFactoryEvents := textureFactory.Events()
 
diff --git a/ui/cocoa/ebiten_window.c b/ui/cocoa/ebiten_window.c
index 01bbf2803..350c0a02a 100644
--- a/ui/cocoa/ebiten_window.c
+++ b/ui/cocoa/ebiten_window.c
@@ -45,6 +45,11 @@ void ebiten_WindowClosed(void* nativeWindow);
   return self;
 }
 
+- (void)dealloc {
+  [self->glContext_ release];
+  [super dealloc];
+}
+
 - (NSOpenGLContext*)glContext {
   return self->glContext_;
 }
@@ -73,7 +78,6 @@ void ebiten_WindowClosed(void* nativeWindow);
   (void)alert;
   (void)contextInfo;
   if (returnCode == NSAlertDefaultReturn) {
-    [self->glContext_ release];
     [self close];
     ebiten_WindowClosed(self);
   }
diff --git a/ui/cocoa/mainloop.c b/ui/cocoa/mainloop.c
index 6be352a72..761747667 100644
--- a/ui/cocoa/mainloop.c
+++ b/ui/cocoa/mainloop.c
@@ -34,7 +34,7 @@ void StartApplication(void) {
   [app finishLaunching];
 }
 
-void* CreateGLContext(void* sharedGLContext) {
+NSOpenGLContext* CreateGLContext(NSOpenGLContext* sharedGLContext) {
   NSOpenGLPixelFormatAttribute attributes[] = {
     NSOpenGLPFAWindow,
     NSOpenGLPFADoubleBuffer,
@@ -46,13 +46,12 @@ void* CreateGLContext(void* sharedGLContext) {
                                   initWithAttributes:attributes];
   NSOpenGLContext* glContext =
     [[NSOpenGLContext alloc] initWithFormat:format
-                               shareContext:(NSOpenGLContext*)sharedGLContext];
+                               shareContext:sharedGLContext];
   [format release];
   return glContext;
 }
 
-void* CreateWindow(size_t width, size_t height, const char* title, void* glContext_) {
-  NSOpenGLContext* glContext = (NSOpenGLContext*)glContext_;
+NSWindow* CreateWindow(size_t width, size_t height, const char* title, NSOpenGLContext* glContext) {
   NSSize size = NSMakeSize(width, height);
   EbitenWindow* window = [[EbitenWindow alloc]
                             initWithSize:size
@@ -87,8 +86,7 @@ void PollEvents(void) {
   }
 }
 
-void UseGLContext(void* glContextPtr) {
-  NSOpenGLContext* glContext = (NSOpenGLContext*)glContextPtr;
+void UseGLContext(NSOpenGLContext* glContext) {
   CGLContextObj cglContext = [glContext CGLContextObj];
   CGLLockContext(cglContext);
   [glContext makeCurrentContext];
@@ -102,16 +100,6 @@ void UnuseGLContext(void) {
   CGLUnlockContext(cglContext);
 }
 
-void* GetGLContext(void* window) {
+NSOpenGLContext* GetGLContext(NSWindow* window) {
   return [(EbitenWindow*)window glContext];
 }
-
-void BeginDrawing(void* window) {
-  // TODO: CGLLock
-  [[(EbitenWindow*)window glContext] makeCurrentContext];
-  glClear(GL_COLOR_BUFFER_BIT);
-}
-
-void EndDrawing(void* window) {
-  [[(EbitenWindow*)window glContext] flushBuffer];
-}
diff --git a/ui/cocoa/texture_factory.go b/ui/cocoa/texture_factory.go
index e39f61374..9007f21e1 100644
--- a/ui/cocoa/texture_factory.go
+++ b/ui/cocoa/texture_factory.go
@@ -1,17 +1,18 @@
 package cocoa
 
-// void* CreateGLContext(void* sharedGLContext);
-// void UseGLContext(void* glContext);
+// @class NSOpenGLContext;
+//
+// NSOpenGLContext* CreateGLContext(NSOpenGLContext* sharedGLContext);
+// void UseGLContext(NSOpenGLContext* glContext);
 // void UnuseGLContext(void);
 //
 import "C"
 import (
 	"runtime"
-	"unsafe"
 )
 
 type textureFactory struct {
-	sharedContext unsafe.Pointer
+	sharedContext *C.NSOpenGLContext
 	funcs         chan func()
 	funcsDone     chan struct{}
 }
@@ -24,7 +25,7 @@ func runTextureFactory() *textureFactory {
 	ch := make(chan struct{})
 	go func() {
 		runtime.LockOSThread()
-		t.sharedContext = C.CreateGLContext(unsafe.Pointer(nil))
+		t.sharedContext = C.CreateGLContext(nil)
 		close(ch)
 		t.loop()
 	}()
diff --git a/ui/cocoa/ui.go b/ui/cocoa/ui.go
index 26e969862..785c39b2e 100644
--- a/ui/cocoa/ui.go
+++ b/ui/cocoa/ui.go
@@ -47,7 +47,7 @@ func TextureFactory() graphics.TextureFactory {
 	return getCurrentUI()
 }
 
-func (u *cocoaUI) CreateWindow(width, height, scale int, title string) ui.Window {
+func (u *cocoaUI) CreateGameWindow(width, height, scale int, title string) ui.GameWindow {
 	return u.textureFactory.createWindow(u, width, height, scale, title)
 }
 
diff --git a/ui/cocoa/window.go b/ui/cocoa/window.go
index 45f7bd98d..852273f83 100644
--- a/ui/cocoa/window.go
+++ b/ui/cocoa/window.go
@@ -4,11 +4,16 @@ package cocoa
 //
 // #include "input.h"
 //
-// void* CreateWindow(size_t width, size_t height, const char* title, void* glContext);
-// void* CreateGLContext(void* sharedGLContext);
+// @class NSWindow;
+// @class NSOpenGLContext;
 //
-// void* GetGLContext(void* window);
-// void UseGLContext(void* glContext);
+// typedef NSWindow* NSWindowPtr;
+//
+// NSWindow* CreateWindow(size_t width, size_t height, const char* title, NSOpenGLContext* glContext);
+// NSOpenGLContext* CreateGLContext(NSOpenGLContext* sharedGLContext);
+//
+// NSOpenGLContext* GetGLContext(NSWindow* window);
+// void UseGLContext(NSOpenGLContext* glContext);
 // void UnuseGLContext(void);
 //
 import "C"
@@ -26,7 +31,7 @@ type Window struct {
 	screenHeight int
 	screenScale  int
 	closed       bool
-	native       unsafe.Pointer
+	native       *C.NSWindow
 	pressedKeys  map[ui.Key]struct{}
 	context      *opengl.Context
 	funcs        chan func()
@@ -34,9 +39,9 @@ type Window struct {
 	events       chan interface{}
 }
 
-var windows = map[unsafe.Pointer]*Window{}
+var windows = map[*C.NSWindow]*Window{}
 
-func runWindow(cocoaUI *cocoaUI, width, height, scale int, title string, sharedContext unsafe.Pointer) *Window {
+func runWindow(cocoaUI *cocoaUI, width, height, scale int, title string, sharedContext *C.NSOpenGLContext) *Window {
 	w := &Window{
 		ui:           cocoaUI,
 		screenWidth:  width,
@@ -116,7 +121,7 @@ func (w *Window) notify(e interface{}) {
 
 // Now this function is not used anywhere.
 //export ebiten_WindowSizeUpdated
-func ebiten_WindowSizeUpdated(nativeWindow unsafe.Pointer, width, height int) {
+func ebiten_WindowSizeUpdated(nativeWindow C.NSWindowPtr, width, height int) {
 	w := windows[nativeWindow]
 	e := ui.WindowSizeUpdatedEvent{width, height}
 	w.notify(e)
@@ -141,7 +146,7 @@ var cocoaKeyCodeToKey = map[int]ui.Key{
 }
 
 //export ebiten_KeyDown
-func ebiten_KeyDown(nativeWindow unsafe.Pointer, keyCode int) {
+func ebiten_KeyDown(nativeWindow C.NSWindowPtr, keyCode int) {
 	key, ok := cocoaKeyCodeToKey[keyCode]
 	if !ok {
 		return
@@ -152,7 +157,7 @@ func ebiten_KeyDown(nativeWindow unsafe.Pointer, keyCode int) {
 }
 
 //export ebiten_KeyUp
-func ebiten_KeyUp(nativeWindow unsafe.Pointer, keyCode int) {
+func ebiten_KeyUp(nativeWindow C.NSWindowPtr, keyCode int) {
 	key, ok := cocoaKeyCodeToKey[keyCode]
 	if !ok {
 		return
@@ -163,7 +168,7 @@ func ebiten_KeyUp(nativeWindow unsafe.Pointer, keyCode int) {
 }
 
 //export ebiten_MouseStateUpdated
-func ebiten_MouseStateUpdated(nativeWindow unsafe.Pointer, inputType C.InputType, cx, cy C.int) {
+func ebiten_MouseStateUpdated(nativeWindow C.NSWindowPtr, inputType C.InputType, cx, cy C.int) {
 	w := windows[nativeWindow]
 
 	if inputType == C.InputTypeMouseUp {
@@ -190,7 +195,7 @@ func ebiten_MouseStateUpdated(nativeWindow unsafe.Pointer, inputType C.InputType
 }
 
 //export ebiten_WindowClosed
-func ebiten_WindowClosed(nativeWindow unsafe.Pointer) {
+func ebiten_WindowClosed(nativeWindow C.NSWindowPtr) {
 	w := windows[nativeWindow]
 	w.closed = true
 	w.notify(ui.WindowClosedEvent{})
diff --git a/ui/ui.go b/ui/ui.go
index 40e9ae320..e64f50300 100644
--- a/ui/ui.go
+++ b/ui/ui.go
@@ -34,10 +34,14 @@ type WindowClosedEvent struct {
 
 type UI interface {
 	PollEvents()
-	CreateWindow(screenWidth, screenHeight, screenScale int, title string) Window
+	CreateGameWindow(screenWidth, screenHeight, screenScale int, title string) GameWindow
 }
 
 type Window interface {
+	Events() <-chan interface{}
+}
+
+type GameWindow interface {
 	Draw(func(graphics.Context))
 	Events() <-chan interface{}
 }