When ⌘F (or the Options menu) is used to switch from full-screen to windowed, the game window is positioned such that the game's titlebar is completely hidden under the system menubar. This makes the window un-movable from the perspective of most users.



(Of note: to anybody else reading this, there's the work-around of holding the ⌥-key and clicking the ‘Window’ menu, then choosing ‘Arrange in front.’)