One of last year's surprise hits was Orcs Must Die!. The game mixed tower defense, action and humor into a package that was incredibly addicting and fun. A highly polished single-player experience, the one thing Orcs Must Die! didn't have was a multiplayer mode. Enter Orcs Must Die! 2. This year's sequel hits all the same high points as the original while also introducing a two-player co-op mode into the mix.

As before, the story plays out via voice-overs from the main characters and intermission sequences. The humor has not been lost, with both the War Mage and the Sorceress expressing distinct personalities. If smartass humor is your thing, you'll feel right at home.

Gameplay is all about keeping the Orc hordes out of the rifts. Before each level, you can choose a selection of weapons, traps and trinkets. Place as many traps as you can afford and then unleash the hordes. As in the first game, skillful trap placement eliminates a majority of your enemies. Those that make it through can be dealt with in combat. It is here that the differences between the War Mage and the Sorceress play out.

The War Mage is a general all-around character, with balanced health and mana. His default weapon is a blunderbuss (AKA shotgun), which launches magic grenades as a secondary attack. The blunderbuss is slower than the crossbow he wielded in the first game, though that weapon can be unlocked. Great against large groups of small enemies, the War Mage feels much like he did in Orcs Must Die!, so veteran players will have an immediate familiarity.

The Sorceress has less health than the War Mage, but more mana. Her default weapon is a magic wand that fires very quickly. Individual shots are weak, but if your aim is true, the Sorceress can take out Orcs in short order. The default attack can be charged up by holding down the fire button rather than rapidly pressing it. The wand's secondary attack is a charm spell, which temporarily convinces an enemy creature to fight by your side. If you charm the strongest creature in a crowd, this little spell can be quite potent. In general, the Sorceress is great when fighting one-on-one with a powerful opponent, but she doesn't always excel at crowd control.

For the most part, the Sorceress shares almost all of the same traps and weapons as the War Mage, though there are some variations. The most visible difference is in the two starter traps since you see those right away. The War Mage's tar trap and arrow wall are replaced with an ice vent and acid wall. They perform similar functions, though the effects differ enough to be noticeable in play. One of the Sorceress-specific unlocks worth mentioning is the polymorph ring. When used, it randomly morphs one enemy into another creature. This is usually a chicken, but it can also be another member of the horde. The ring's secondary attack turns the Sorceress into an ogre so she can dish out melee damage.

Disappointingly, it is impossible to switch between characters once you have chosen one or the other. If you wish to swap, you must start an entirely new game with the other character. Nothing carries over. Given the fact that the rest of the game offers extreme flexibility in trap selection and upgrades, this is an odd artificial limit to impose on players.

The upgrade system has been unified in Orcs Must Die! 2. The Weavers and their level-specific upgrades have been removed. Now, all traps, weapons and trinkets are upgraded individually in the spellbook. Each upgrade costs a set number of skulls. You are free to experiment, as spent skulls can be refunded at any time. Oddly, there is no option to refund individual upgrades. This means if you do wish to change a single option, you have to reselect upgrades for every item. It's clunky, but it works.

Level design is once again solid, with each map requiring thoughtful use of your arsenal. If there are any flaws in the map selection, it is that the pendulum may have swung a bit too far in the co-op direction this time around. Some of the final maps seem to be designed for co-op first, with the solo player as an afterthought. They're all doable as a single player, though you might run back and forth a lot.

At first glance, the 15-level story mode makes it sound like Orcs Must Die! 2 offers less content than its predecessor, but there's more here than just story mode. Endless mode offers up 10 maps that send wave after wave of progressively more challenging Orc hordes after you. Five of the endless maps are reused from story mode, but the other five are all new. There's also the weekly challenge, which tasks you to master a specific map under certain constraints. Toss in the fact that each level feels different when playing co-op, and there's plenty to keep you busy.

Players who happen to own Orcs Must Die! on Steam also get access to classic mode, which brings 10 levels from the original into the sequel. The levels haven't changed, but you get to play around with the new toys as well as giving them a go in co-op. Those who purchased the original on the Xbox 360 are out of luck as far as classic mode goes, but given that the first game has been on sale for less than $4 recently, rebuying it on Steam just for classic mode won't break the bank.

Speaking of Xbox 360 players, if you're coming from a controller, Orcs Must Die! 2 has you covered. The game plays just as well with an Xbox 360 controller as it does with a keyboard and mouse. Default sensitivity was a bit high in either case, but once you turn that down, control is spot-on.

Online play is great, with no noticeable lag or hiccupping during our test games. You do need to plan your games out in advance since Orcs Must Die! 2 doesn't have any sort of matchmaking. The only way to play co-op is to manually invite someone into your game.

Voice chat is supported in co-op, though that aspect of the net code is sub-par. You can generally make out what the other person is saying, but random voice drops and delays happen constantly. A better option is to disable the in-game chat and use a third-party solution or the default Steam chat client.

Like its predecessor, Orcs Must Die! 2 is a straightforward game, but it's also an extremely enjoyable one — doubly so if you have a friend to play alongside. Whether it's a return trip or your first time wading into the horde, this is one tower defense game worth checking out.

Score: 8.5/10