Tower defence games can sometimes feel like passive experiences. Mostly because there's usually a downtime after setting up your defences during which all you can do is sit back and watch, but also because there's very little you can do to correct your mistakes once they've become apparent.
Orcs Must Die masterfully solves both of these issues by letting you enjoy the tower-defence gameplay you love with all the kinetic and immediate feedback of a third-person shooter. Rather than the detached, omniscient overhead perspective, Orcs Must Die puts you in the boots of a War Mage who is left to protect a series of fortresses and the magical rifts they contain.
You'll run around the fortress as you set up your defences, inspecting the route between the gates (the orcs' entry point) and the rift, trying to find the best choke point. This makes a huge difference in the way you play this type of game. Some of the traps that you can set, like spikes that come out of the ground or tar that slows the orcs, could have been managed from an aerial perspective, but some of my best defences have been set up in narrow hallways-turned-meat grinders with traps pushing spinning blades out of the wall or mallets swinging from the ceiling.
Other tower defence games have similarly tried to make things more exciting by giving you an avatar and putting you in the middle of the action, but Orcs Must Die stands out by really taking advantage of its three-dimensional space. There are stages when you have to run up and down stairs to manage orcs that are coming at you from different floors, and stages when your main advantage is having the upper-ground, where flying enemies (introduced later in the game) can really catch you unprepared.
However, unlike most tower defence games, making a mistake here is not the end of the world. The War Mage you control cannot only set up traps, he is also equipped with a crossbow, a sword, and magic spells. The action is not on the level of top tier third person shooters like Gears of War, but it's not inconsequential, either. You can zoom in with the crossbow and slow down your firing rate to land headshots that instantly kill most enemies, and knowing how to do this sometimes makes the difference between winning and losing. You may not notice that you left one path undefended, but if you can get there fast enough and properly use the tools you're given you can save the day.
Thankfully, the tools are plentiful. You start out with a few simple floor traps and gain a new kind of trap at the end of almost every level. Some levels are clearly designed to teach you how to use a certain trap, but you spend the majority of the game choosing the traps that best suit your strategy and style of play. This makes the game consistently challenging, but also enjoyable, as it's not about figuring out the one correct way to survive the attack; it's about figuring out what best works for you.
My strategy was usually to keep my distance, spending my money on many cheap defences to slow the enemies down while a battery of archers and I fired at them from afar. I set up a few of the expensive and more lethal traps only as fail-safes in case any orcs slipped by.
Sometimes there are a hundred orcs coming right at you, and it doesn't even seem possible to take them all on. Orcs Must Die may not be as technically impressive as some top tier action games, but many of those game could learn a thing or two from how immensely satisfying it is to watch those hundred orcs step into your kill box and get completely annihilated.
And the traps are not even all the tools at your disposal. Later on you can choose from more weapons, more spells, and three skill trees are introduced, adding a RPG element you can use to complement your style of play.
I loved Orcs Must Die and would recommend it to anyone, especially those who tired of or never liked the tower defence genre to begin with. I would have given it a perfect score were it not for a few minor problems.
Orcs Must Die deserves a much better protagonist. The War Mage looks fine; he's just a more stylised take on Nathan Drake in robes (at this point all game protagonists are some sort of a take on the Uncharted hero). The problem is that he's a stupid jerk and he always has something to say. This was the intention of the developers -- to make a stupid jerk protagonist in the vein of Duke Nukem or Serious Sam -- but seeing as how he's not very funny, he ends up doing more harm than good.