how to create a black rounded-corners window in cocoa

How to create a round开发者_高级运维ed corners black window in cocoa? Is it standard and can be created by IB? Can somebody provide an example?

You can create an NSPanel from the standard IB library. It is dark gray and translucent (not black though), and has rounded corners.

Here is a screenshot: http://grab.by/45kJ

In the library it is referred to as a HUD Window.