Angry Birds and other game apps

Do you use "data" time when you are playing games, like Angry Birds?  I know when you download, of course you do, but what about when you are playing the game?

Thanks so much, that is what I was assuming, but the game took up the whole screen so I couldn't tell.  I don't want to keep playing and get a huge bill!    Then explain to my husband, "oh, I was playing Angry Birds!" 

When I am running the free games those ad are running data?

I just downloaded the official angry birds game, and I noticed it has ad's. Almost ANY free application is going to have ad's. If it has an Ad, it uses data. However, you probably won't go anywhere close to over your data plan. If you have wifi, have it active at all times. If you don't, you should still be fine. I play a multiplayer game in school, where we have no wifi, and I have tons of data left of my $15 plan.