Share a variable (points) between two differents Project

Hello everybody!

I am working on a project and I can't solve an issue.

I have created a "Main Project", with 3 images.

I have created 3 "Games projects".

Every image on the "Main Project" is a link to one of the three videogames.

So, you enter the "Main Project", you choose the game, you play.

At the end, you can come back to the "Main Project".

Now: how can I share the "points" between the game and the main projects?

If I do 5 points in the game, I need to have a variable with the value of "5" in the Main Project.

I need, for my beta test, the easiest way! Can someone help me?

Thank you very much!!!!!!!!

I hope I was clear :)