It's been nearly two years since Angry Birds crashed through some glass panels and into hearts. Half a billion downloads is certainly worth celebrating. Developer Rovio has announced that new content is coming to Angry Birds to celebrate the anniversary.

Titled 'Happy Birdday,' the December 11-due update includes new achievements and art alongside fifteen new levels, and also unlocks all of the Angry Birds episodes so that they don't have to be earned via standard game progression.

The update also adds a new "Rovio Channel" that lets players access Angry Birds-worthy "news, games, videos, Facebook [content], [the] Angry Birds shop, and other great content."

A handful of big retail outlets are also celebrating with special Angry Birds-themed events. Barnes & Noble will host special events and giveaways "from 11 AM to 3 PM on December 11," including a scavenger hunt where players can earn entries to a raffle for Angry Birds prizes. Some stores will also have "coloring or high score contests, design your own Angry Birds character, [and] Angry Birds Parades and guessing games."

Toys 'R' Us is also getting in on the 'birdday' action on December 11, offering "25% off Angry Birds plush toys plus a code that unlocks an Angry Birds Chrome Seasons' Greedings bonus level."

I, for one, will be celebrating the triumph of the Angry Birds franchise by eating a lot of bacon.