There are several styles for the Compass window that you can choose.
There is nothing shown when the window is concealed. The window is invisible with no graphics or controls to minimize the amount of memory used. Nothing will appear on the screen when you attempt to activate the window.
This is the "round" style compass.
This is the small normal "strip" style compass.
This is the large normal "strip" style compass.
This is the combination small and large normal "strip" style compass.
Note: The above images are only sample styles.