The topic of today’s article is a game which is roughly eight years old, and which resides in the curious genre of tower defense: Defense Grid: The Awakening. I call tower defense a curious genre because the formula of tower defense is a simple one, and yet one which is rather often poorly executed. For this article, I just want to talk about what that formula is, and how Hidden Path managed to impeccably nail it (in addition to doing other things right).
It is amazing to me that Defense Grid is almost a decade old now, as I first played it less than two years ago and, due in no small part to its economical aesthetics, the game still felt fresh and new. In short, it has aged incredibly well so far. Indeed, what is perhaps most striking is the fact that so very many tower defense games have been produced in the eight years since Defense Grid released, which by and large continue to make the same mistakes that Defense Grid so gracefully and thoroughly avoided.
The Tower Defense Formula and Defense Grid:
The basic formula of tower defense games is as follows: progressively more difficult waves of enemies traverse the playfield while the player manages the choice and placement of different kinds of stationary defensive units to cease the enemies’ march. Sure, there are other common elements and variations, but pretty much anything that bears the name of ‘tower defense game’ has at least that much. Where most entries to the genre fail is in insufficient or uninteresting variety and balance—of towers, upgrades, and enemies.
One of the first things that began to really impress me as I played through Defense Grid: The Awakening was its tower variety. Usually there are a few options that are a bit lackluster, but I found myself adding each and every new tower to my plans as each was introduced. The towers are almost universally useful, interesting, and well-thought-through as regards enemy weaknesses and strengths. While a couple of tower options fulfill similar roles (there are two primary short-range group-control towers, for instance), each individual tower has pros and cons which actually impact whether one or the other will yield better results for a given set of enemies.
More impressive than its tower variety, from my perspective, is Defense Grid‘s balancing of upgrades. The resource costs of upgrades are as high as usually found in such games, but in return one receives substantive damage, range, or effect boosts. Having both a solid upgrade system and a solid tower variety means that build decisions and build order are vital to victory, and lead to some intricate planning in more difficult stages and challenges. Add to these strengths the game’s most unique gameplay element—a resource interest rate tied to how many ‘power cores’ remain in the housing that you are protecting on each map—and timing becomes as important as planning.
Generally a tower defense game will get either tower balance or upgrade balance correct, but not both. Failing on either of these is the clearest way that most of the huge number of browser and professional TD games I have played have lost my interest. If tower balance is lacking, an efficient player will just carpet the lanes with the tower that has the best power to price ratio. If upgrade balance is lacking, an efficient player will just carpet the lanes with a huge number of cheap low-level towers rather than spending any resources on upgrades.
Another solid area of Defense Grid‘s design is its middleground approach between determined tower placement locations—like in OTTTD and Kingdom Rush—and near-total placement freedom—like in Orcs Must Die!. Defense Grid only allows the player to place towers on grid squares, but different maps implement the squares differently. They range from surrounding the lanes in small localized groupings to being a canvas-like mat across which the enemies will march unless mazed. This seems very straightforward, but I can only think of a handful of games which have used this balanced approach in the intervening years, such as Sanctum.
Further Virtues of Defense Grid:
It’s not to be discounted that this is also one of the few tower defense games I have ever played which includes flying enemy units without making me feel like those flying units are either cheap or trivial. When they’re cheap, a tower defense game will slot them in as bosses or unexpected challenges which seem to spit in the face of all of the design work which the player has done until their arrival. When they’re trivial, they will be attacked by all of the same towers as the ground units, or they will be bafflingly restricted to the same path as the ground units.
Instead, in Defense Grid, a tracing line at the beginning of each level (and which can be called back up throughout) indicates not only the presence of air units in that level, but also their path of attack. Air units are balanced by being very harsh with power cores (if an air unit picks up a core, it is lost even if that unit is later destroyed), but being totally obliterated by the air defense missile towers. In this way, the player has a further challenge to consider, but provided that the player is careful enough in planning the resource requirements and best placement of one or more missile tower(s), they will have no problem dealing with flying enemies. Rewarding the player for planning things out and thinking critically is precisely the proper way to construct a mechanic in a genre that is ostensibly all about planning a bulwark against future offenses.
I would also like to praise Defense Grid: The Awakening for its storytelling, which involves no cutscenes and never interrupts the player’s control of the game. Most of the story of the game—and of the expansion campaigns—comes to the player through the narration of Fletcher, a virtual representation of a now-dead soldier, who advises and guides the player in defending the planet from the invading alien forces. The strength of this fairly standard science-fiction story can be credited secondarily to the writing, but primarily to the excellent voice actor behind Fletcher, the extremely talented Jim Ward (who gamers may recognize as the vocal talent behind Captain Qwark from the Ratchet & Clank series, although the two roles are very different).
The optimization of Defense Grid is something else that impressed me. While it may be true that the game runs smoothly in large part because I am running an eight-year-old game on a four-year-old computer, there are no dropped frames whatsoever despite the very nature of the game involving immense numbers of entities on-screen with a huge number of explosion effects happening in rapid succession. To demonstrate this point, the image a few paragraphs below is a screenshot from near the end of a ‘super grinder’ challenge, during which I was making use of the speed-up function which runs the game at double speed, at a moment when about 20 towers were firing simultaneously on a wave of about 40 aliens. The mess you see below ran silky smooth . . . on my laptop.
Another commendable part of this game is Hidden Path’s post-release support of it. Apparently there were complaints from early reviewers about the UI and a low number of levels. But I didn’t know any of that until I started doing research for this article, because in the years since its release Defense Grid: The Awakening has been patched and improved a number of times, at no additional cost to the player, with bonus challenge missions, UI updates (both menu and in-game), optimization improvements, and more.
Speaking of additional cost, however, one last nice thing I want to mention about Defense Grid is that it was released in the era between when DLC became the primary delivery method of game expansions and when DLC became an inbuilt, supplemental cashgrab for many development teams. As such, its expansions are conveniently and inexpensively available for online purchase and download alongside the game, yet remain highly substantial in offering commensurate chunks of content at the same level of quality as the base game.
One strange thing about this game is that it bills itself as a ‘unique take’ on the tower defense formula at the top of its Steam page. Yet, with the possible exception of the power core interest mechanic, this game ticks all of the conventional boxes. But often a good game is not wholly—nor even, necessarily, partially—innovative. A good game can be constituted entirely by a good execution of a solid design. Defense Grid: The Awakening is a phenomenal execution of a solid design.
Tower defense is a genre that has always attracted me. I love the idea of passively managing a defense in a game every once in a while (as a change of pace from actively managing an offense); I love the idea of optimizing a tight path design with complementary defensive abilities to deal with large amounts of enemy units in minimal time and space; and I love the prospect of singlehandedly fending off droves of assailants. Defense Grid lets me do all of that while providing meaningful challenges and dodging the potential pitfalls of its unique Strategy subgenre.
 The most common variations are, first, between games that have fixed tower locations and games that have open fields that act as both lanes and possible tower locations; second, between games wherein the enemies only have to traverse the lanes, and games wherein the enemies have to fetch a resource and then travel back out along the lanes again; third, between games wherein the player only manages towers and games wherein the tower management is allied to other capabilities (e.g. special attacks, an FPS player-character, etc.); and fourth, between games wherein the towers themselves are susceptible to being damaged or spent, and games wherein they are invincible except through action by the player.
 As an aside, mazing towers to shape the enemies’ path is easily one of the most enjoyable things to do in a tower defense game, and any attempt at tower defense which releases without that capability in at least a fair number of its levels would have to do a lot of other things very right to compensate for that omission. Plants vs. Zombies, for instance, managed to win me over despite lacking path control by providing a huge number of viable tactical options (i.e. plants).
 Incidentally, included among the small set of DLC options is a campaign that is a tie-in with Portal and which sees Ellen McLain’s GLaDOS temporarily joining the narration (and story) alongside Fletcher; if you, like me, prefer the impersonal, efficient tone of GLaDOS in the original Portal, then you will definitely enjoy that expansion.
Towering Tower Defense: