The tower defense genre is a rather crowded market at the moment. Most would trace the history of such games back to a particularly addictive Warcraft 3 mod, and most will make the mistake of lumping Robot Entertainment’s multiplatform title Orcs Must Die! in as part of that comparatively recent offshoot. In reality, OMD draws most of its strengths from much more venerable stock, blending the gameplay of 1994′s The Horde and Tecmo’s Deception series. But do the charms of those mid-90s hits hold up in the year 2011? Read on and all will be answered – just mind the spike trap under the doormat.

Stepping into the armored boots of the War Mage – an infectiously cheerful wisecracking idiot hybrid of Charlie Sheen and Bruce Campbell – you’re tasked with defending 24 castles and their respective magical rift-gates from an army of angry orcs, ogres, kobolds, gnolls and a few other generic fantasy tropes. Anyone familiar with the Tower Defense genre knows how this goes. Enemies come in from point A (and later, points B, C and D) and make a bee-line towards point Z. You place defenses and traps in their path to stop them from reaching their objective, as if too many get through, it’s game over.

Aesthetically, the game is largely familiar stuff. The art-style is quite reminiscent of World of Warcraft, with the exaggerated lighting and cartoonish proportions on the characters and monsters lending it some immediate (if slightly generic) charm. This is unquestionably an instant action game, with the plot relegated to three short (and skippable) animatics over the course of the campaign, and a few short internal monologues from the main character, which don’t interrupt the gameplay at all. Aside from the constant cheerful wisecracking and self-aggrandizement of the motormouth protagonist, the game makes it fairly clear that you’re not meant to be messing around here and pondering the meaning of life. You’re supposed to jump in, build traps and mulch a whole lot of monsters to an enthusiastic fantasy-metal soundtrack.

What sets this apart from its genre contemporaries and encourages comparisons to The Horde and Deception is the perspective. Rather than smiting your foes from the perspective of an omnipotent overseer, you’re right there on the front lines with a crossbow, sword and a variety of spells to cast. In terms of raw control, it feels like any third/first person shooter. Your weapons are responsive and accurate, and headshots help thin out the orc hordes a lot quicker than just firing wildly. Movement is fast and precise, with sprinting and jumping letting you cover the required distances with surprising ease. At the start of each level, you’re told the types of enemies you’ll be seeing, and can pick out what personal weapons and placeable traps would best help in your mission.

Rather than building towers, you build your defenses into the walls, ceilings and floors of each castle, trying to string together traps in the most efficient possible fashion. A springboard trap built into the floor will do very little damage by itself, but placing a set of whirring grinders on the wall above and behind the launcher will catapult orcs up and into the deathtrap, awarding a modicum of bonus cash for stringing together damage sources, and if the poor orcs are lucky enough to survive, then they have to navigate the springboard trap yet again. While the game is a purely solo affair (global leaderboards are the only interaction you’ll have with other players), you’re not entirely alone. Among the traps are remarkably capable soldiers and archers, although they’re by no means essential for a successful defense.

There’s a remarkable number and weapons of traps to pick from – one unlocked after each level – so there’s a lot of room for players to experiment and mix things up, looking for new combinations that leverage the layout of each castle to their advantage. Most castles have a few built-in hazards as well, with permanent obstacles to throw enemies into such as acid pits, and single-use ‘smartbomb’ traps such as precariously fastened chandeliers, vats of boiling acid perched on ledges and rolling logs waiting to be unfastened above staircases. These are typically activated by shooting them, and are only usable once per level but can do massive damage if timed right. It helps to be aware of your environment, and it gives you a good excuse to properly scout out every inch of the cartoonish castles in the pauses between waves.

While initially starting out very simplistic (the demo levels are particularly poor examples of the later gameplay), the castles expand quite dramatically over the course of the 24 missions, with later stages often featuring three or four entry-points for enemies, as well as a multitude of branching paths for them to run down. The difficulty ramps up fairly consistently through the campaign, and completion of all levels (Steam estimates this took me between 7 and 8 hours) unlocks a whole second ‘Nightmare’ campaign, putting you right back at the start with all your collected weapons and traps intact, ready to face down expert-level remixes of all 24 stages. Having run headlong into a brick wall of difficulty around Level 6 of Nightmare mode, it’s safe to say that there’s no shortage of content or challenge available here.

Completing the game is only part of the experience, though. At any point, you can replay previously completed levels (and take all unlocked traps and upgrades along with you) in search of a 5-skull reward, achieved by completing a level with no respawns, no enemies escaped, and coming in under a set par time. These skulls can be spent on permanent, small upgrades or discounts for each of your traps, permanently making them slightly more useful. On top of this, there’s the perpetual competition over the high score board, with global and friends-list rankings for each level kept nice and seperate. Given the amount of freedom afforded to players, there’s a lot of choice and experimentation involved in finding the highest-scoring trap combos. While it might be more efficient to just crush your enemies quickly, you might earn more points by toying with them, flinging them through the air and building up multi-trap combos. There’s definite replay value here.

There’s really not much to complain about here. OMD achieves everything it sets out to do, and the only potential problems are those of omission. After playing Sanctum, the lack of any cooperative mode feels a little odd, a replay function (even if just for friends) to see completion techniques for other players would have been nice, and I found myself wishing for some kind of sandbox map where I could just play around with infinite resources and let me experiment with unusual trap combinations without having to save up money from kills in a campaign level. The opening levels are possibly a little too narrow and restrictive, making the demo likely to turn some players away, but even that complaint vanishes when you get to Nightmare mode and find that there’s some interesting challenges inherent in defending a single, tight corridor from overwhelming enemy forces with limited resources. In the end, all I can come up with is some mild nitpicking and a few minor glitches on show, such as orcs getting ‘lost’ in the middle of an open hallway after being thrown by a physics trap, or stuck up on a high ledge out of sight after an unusually successful encounter with a springboard. Nothing that a small patch can’t rectify.

Orcs Must Die is an accessible, charming and well paced bit of arcade action/strategy. Solid aesthetics back up a game with remarkable depth and variety, a good amount of content for the asking price, and plenty of incentive to go back and do it all again as soon as you’re finished. The traps are inventive, the levels are varied enough to be memorable in their layouts, and it’s just plain satisfying to watch your enemies exploded into showers of cartoonish kibble – violent and visceral, but just silly enough to scrape by with a Teen rating at the end of the day.

Orcs Must Die! is out now on the Xbox 360 via XBLA and is due October 12th for PC via Steam, priced at $15/1200MS Points.