If you’re the only Windows Phone user on earth who doesn’t have Angry Birds yet, now’s the time to jump: A new version of the original game is available for free until May 15. Actually, you may want to snag this even if you already have Angry Birds, as this version comes with an additional 100 new levels.

“We have a brand new version of the original Angry Birds for our fans on Windows Phone to play,” a Rovio blog post notes. “The game will have over 400 levels from the get-go, and will be free to download for the first two weeks. The Windows Phone 8 version will also have Xbox Live integration with new achievements and leaderboards!”

Of course, that last part of the quote suggests that the version of this game for Windows Phone 7.5 does not including Xbox Live integration.

Another oddity: This game is indeed completely separate from the original release of Angry Birds, which Rovio says is because “it will be technically easier to support in the future.” Downloading this new, improved version of Angry Birds “will not wipe your old game, including your stars and level progress. Both versions are completely separate.”

Download Angry Birds for Windows Phone 8

Download Angry Birds for Windows Phone 7.5

A post to the Windows Phone Blog notes that Angry Birds Rio is on the way for Windows Phone “very soon” as well. (Angry Birds Space and Angry Birds Seasons are already available.)