diff --git a/ui/cocoa/ebiten_window.c b/ui/cocoa/ebiten_window.c
index 460708522..01bbf2803 100644
--- a/ui/cocoa/ebiten_window.c
+++ b/ui/cocoa/ebiten_window.c
@@ -25,18 +25,13 @@ void ebiten_WindowClosed(void* nativeWindow);
                             styleMask:style];
   NSScreen* screen = [[NSScreen screens] objectAtIndex:0];
   NSSize screenSize = [screen visibleFrame].size;
-  // Reference: Mac OS X Human Interface Guidelines: UI Element Guidelines:
-  // Windows
-  // http://developer.apple.com/library/mac/#documentation/UserExperience/Conceptual/AppleHIGuidelines/Windows/Windows.html
-  NSRect contentRect =
-    NSMakeRect((screenSize.width - windowRect.size.width) / 2,
-               (screenSize.height - windowRect.size.height) * 2 / 3,
-               size.width, size.height);
+  NSRect contentRect = NSMakeRect(0, 0, size.width, size.height);
   self = [super initWithContentRect:contentRect
                           styleMask:style
                             backing:NSBackingStoreBuffered
                               defer:YES];
   if (self != nil) {
+    [self center];
     [self setReleasedWhenClosed:YES];
     [self setDelegate:self];
     [self setDocumentEdited:YES];
diff --git a/ui/cocoa/mainloop.c b/ui/cocoa/mainloop.c
index 8f54a39de..6be352a72 100644
--- a/ui/cocoa/mainloop.c
+++ b/ui/cocoa/mainloop.c
@@ -10,12 +10,16 @@ void initMenu(void) {
 
   NSMenu* menuBar = [NSMenu new];
   [NSApp setMainMenu: menuBar];
+  [menuBar release];
 
   NSMenuItem* rootMenuItem = [NSMenuItem new];
   [menuBar addItem:rootMenuItem];
+  [rootMenuItem release];
 
   NSMenu* appMenu = [NSMenu new];
   [rootMenuItem setSubmenu:appMenu];
+  [appMenu release];
+
   [appMenu addItemWithTitle:[@"Quit " stringByAppendingString:processName]
                      action:@selector(performClose:)
               keyEquivalent:@"q"];
@@ -49,21 +53,19 @@ void* CreateGLContext(void* sharedGLContext) {
 
 void* CreateWindow(size_t width, size_t height, const char* title, void* glContext_) {
   NSOpenGLContext* glContext = (NSOpenGLContext*)glContext_;
-
   NSSize size = NSMakeSize(width, height);
   EbitenWindow* window = [[EbitenWindow alloc]
                             initWithSize:size
                                glContext:glContext];
+  [glContext release];
+
   NSString* nsTitle = [[NSString alloc]
                       initWithUTF8String:title];
   [window setTitle: nsTitle];
   [nsTitle release];
 
   [window makeKeyAndOrderFront:nil];
-
   [glContext setView:[window contentView]];
-  [glContext release];
-
   return window;
 }