How do you speed up the mac screen black after the screen is locked?

I've been a mac os x high sierra in my room and zock at night secretly always some games. The thing is that my mother still looks netflix in the evening and zwischendruch still stands up and I see if I spiele.mein room is right next to her I hear when she comes. I then always press -control- command- q-. And sometimes it is too late and you can see that he is still on. Could you tell me how I can speed it off, or the screen?

Try it:

apple + alt + eject

fast rest

Or you take a black picture as a slideshow ;-)

Does not know how to do that