My Macbook shuts down when I try to play a game or a video.

So i just woke up this morning and tried to play a game that i have (WoW) but then as soon as i logged in, my macbook shut down. I also tried to watch a video online and then the macbook shut down again. can anyone tell me what they think is wrong? Any help is appreciated please. thank you

One of the possible reasons could be overheating. What kind of surface are you using your MB on? For proper ventilation, use it on a hard surface that allows for proper airflow. Secondly, are the fans clogged? Removing any dust or other impediments using something like a can of compressed air will allow the fans to operate to their fullest potential.

Also sounds like a possible graphics hardware/driver problem.
I'm not a mac expert so I can't help specifically.. might give someone else an idea though.