Open a transparent Window in PTB

Can I open a transparent window using “PsychImaging(‘OpenWindow’,…)”?
I have an idea to show some visual stimuli when play a video game.
So I need a transparent window background through which the game screen can be seen.
I try to use “PsychDebugWindowConfiguration(1,0.5);”, but the stimuli also become transparent.
Is there any way to achieve it?