Google upped the ante in its challenge to Facebook Thursday by introducing games into its nascent social network Google+.

Just as in Facebook, Google+ users will now be able to play games such as Angry Birds, Zynga Poker, and Crime City — and bug their friends with notices of their latest achievements and high scores.

But Google promised Thursday there’s a difference between its network and Facebook’s — those notifications won’t show up in the general “stream” of updates users see. So you’ll only run across your friends’ gaming-centered notifications when you go to play a game yourself.

Google says it’s starting now with just a few handpicked titles, but that it’s looking to work with more developers — announcing a developer’s blog — where many hope Google will soon announce an API for Google Plus.

The announcement isn’t unexpected. Google’s going head-to-head with Facebook to try to win back the identity/sharing war that Facebook has won. And games have been a huge part of Facebook’s success, bringing users back daily to raise virtual chickens or run virtual street gangs.

Zynga, built almost entirely on top of Facebook’s platform, has filed for an IPO and reported that it made $16.8 million dollars in net income the first three months of the year, while booking $243 million in revenue — nearly all of that money coming from power Facebook users.

Google’s games announcement shows that it’s doubling down on its bet that users are tired of Facebook’s sharing model that makes it difficult to share information with only a select group of users.

[S]haring is about more than just conversations. The experiences we have together are just as important to our relationships. We want to make playing games online just as fun, and just as meaningful, as playing in real life.

That means giving you control over when you see games, how you play them and with whom you share your experiences. Games in Google+ are there when you want them and gone when you don’t.

Facebook games often reward users who announce their “achievements” to their friends, which the games hope will land them new users. But the side effect has been a growing weariness among many Facebook users upon seeing those notifications about how many chickens their friends now have on their virtual farms.

Google says its new Games page will be rolling out to users in waves.