Robot Entertainment announces plans for Orcs Must Die! 2, saying the sequel to their AIAS award-winning action/strategy hybrid will come exclusively to personal computers this summer. This is a direct sequel, starting off all of 48 hours following the conclusion of the first game, and it will offer exclusive content for those who own the original, which they say has been responsible for the demise of 3.4 billion orcs since its release. The game will be playable by attendees of PAX East next week, so we'll be hearing more about this soon, and in the meantime, here's an announcement trailer and here's a list of new features, including the oft-requested multiplayer support in the form of co-op:

• New Campaign – Orcs Must Die! 2 features a full campaign that you can play in single-player or with a friend in co-op. Choose to play the campaign as the War Mage, a headstrong hero who charges into danger, or play as the more nuanced Sorceress, a new hero who keeps enemies at bay with mind-control and magic.
• More Enemies – An army of vile new creatures is set to pour through the rifts, and they’ve brought all of your favorite trap-fodder from the original Orcs Must Die! along with them!
• More Defenses – Orcs Must Die! 2 has an enormous armory of new and classic defenses, including an all new assortment of magical trinkets. Use your new spellbook to buy defenses and upgrades the way you choose to, building up your arsenal based on how you play the game.
• New Upgrade System – The skull system has been completely redesigned. You will always earn skulls for replaying levels, and the skulls can be spent on multiple persistent upgrades for each of your defenses.