After months of closed beta testing, PixelJunk Monsters Online is officially open to all on Facebook. After a number of successful games on PlayStation Network, this is developer Q-Games' first foray into social games with the PixelJunk brand.

PixelJunk Monsters Online plays very similarly to the original tower defense game on PS3 and PSP, letting players build and buy towers to survive an increasingly powerful onslaught of enemies. New to the social version is a world map system that promises to add "a brand new strategic layer to the game."

Players can expand their territory on the world map by defending their tiles. As more friends join in, you'll be able to compete for gold crowns, as your performance is ranked amongst your friends.

As with most social games, the game is free to play at first. However, you'll be able to buy new towers, maps, and items by using in-game currency. Q-Games promises to push updates "regularly," which should help enable PixelJunk addicts continue clicking away.

You can check out the game on Facebook by clicking here.