Steam's Daily Deal has dusted off a fantastic co-op game all PC players should try out. Trine 2: Complete Story includes the Trine 2 core game and integrates the Goblin Menace DLC along with the unlockable Dwarven Caverns level, all for an impressively small amount of cash.
As puzzle platforms go, it's tough to beat Trine 2. The genre isn't exactly everyone's favorite in this modern age of first person teabagging simulations and candy farming games (or whatever those Facebook things let you do), but it's ripe territory for an amazing cooperative experience. Trine 2 puts players in control of a wizard, knight and a thief as they work through a gorgeous fantasy world. Each character has his or her own abilities that must be used in concert to proceed. The wizard can levitate foes and spawn crates the others can stand on, the thief has deadly arrows and a handy invisibility cloak, and the knight carries a big hammer that can smash anything in his path. Our Trine 2 co-op review spells out all the lovely details.
Trine 2: Complete Story is only on sale for a day. The 90% discount applies to the 3-pack as well, which is convenient since it supports three player local or online co-op. If your friends aren't as fast with the "add to cart" button as you, do them a solid and gift a copy posthaste.