How to make a game full screen on my external monitor?

Using google i came upon this page: Full screen app mode doesn't play wel with external displays.

Now this is only with fullscreen apps but I think it might be the same problem. Reading a bit futher in the comments i found this :

Just go into System Preferences > Displays > Arrangement and move the white menu bar strip to the external monitor’s rectangle. Full screen apps seem to associated only with whatever is considered the primary display.

Ps: Don't have osx so I wouldn't know if this works...

You might be able to do it using F7 or FN+F7:

I believe that the standard F7 key is to change display modes when hooked up to an external monitor or projector.

It should look like this with a helpful ambiguous icon:

I'm running OS 10.9.3 using a MacBook Pro 17" with retina display connected to a 27" Studio (Thunderbolt) Display. I mirrored the displays, then selected optimize for Thunderbolt Display. When I want to use both screens, I just deselect Mirror Displays, and it switches right over. It's the only decent way I've found to play games or watch movies/TV on my Studio Monitor, but it works fine!

Just wanted to add since it might help someone:

if you get a blank built in monitor after going full-screen on an external one

put the app you still want to use (like Safari for example) in full screen mode on built in monitor BEFORE putting your game full-screen on an external one.

This way you can play your games full screen and still browse a bit in Safari for example ..

There are at least 3 Ways:

Via Mission Control. Launch the game, swipe up the trackpad with 3 fingers (or press F3/Fn+F3, then drag the game window into the second monitor/desktop.

Via Dock. Move your mouse to the second screen and to where your Dock is positioned to activate it on that monitor. If the game is on the Dock or in the Applications Folder, launch it from there.

Via Finder on the Second Monitor. Open a new window in the second monitor, then Open the Applications Folder or where the Game is located (if it's other than the Applications folder), then launch the game from there.