There's this one Calvin and Hobbes strip that really gets at a truth of human nature. Calvin is standing in the snow describing the snow fort that he and Hobbes are going to build. It's going to be a huge affair, with multiple redoubts and turrets before anyone even gets close to the main wall. Then he and Hobbes start to build the thing and they find that the snow doesn't pack well, the job will be difficult, and they're cold. So the next we see of them, they are sitting next to the living room fireplace drinking hot cocoa, and Calvin is drawing a plan of a snow super-fortress. He says, "This is more fun that actually building the fort anyway. Now where should we put the icicle spikes?"
This is the appeal of the tower defense genre: it permits all the imaginative joy of planning without the frustration and futility of execution. Everything is either invariable or foreseeable. The enemy can't disrupt the player's activity, nor is the player bombarded with micromanagement tasks that cumulatively decide the outcome of the game. The enemies try to follow a path across the map; the player stops them. Tower defense games give players a tremendous degree of control, because their defensive layout is the only important variable.
The knock against tower defense games is that they lack strategy or even significant choices. Your only objective is to interdict a bunch of mindless drones, called "creeps" in tower defense, on their way to Point B. You usually have a single resource, which you collect by killing the mindless drones you were going to kill anyway, and your only options center on choosing where to build your towers, and whether or not to upgrade them. Tom Chick called them RTS's "for basebodies," because they act like RTS without the rushing and booming, leaving only turtling. On the Three Moves Ahead podcast, panelist Bruce Geryk commented that tower defense is inherently a static defense, and static defense is inherently dull.
This strategic perspective overlooks the gratifying aspects of employing traps and killzones against an attacking enemy. There is something darkly satisfying about seeing your enemy advance into the meat-grinder that you've devised for him, then get destroyed. It's candy for the inner-sociopath, and even good people can find it alluring. Remember that Robert E. Lee made his famous, "It is well that war is so terrible, lest we should grow too fond of it," comment at the battle of Fredericksburg, where he was watching Confederate fire scything down wave after wave of Union troops as they attacked. Having an enemy attack a perfectly-prepared defensive position might not make for much of a battle, but sometimes you don't want to fight a battle. Sometimes you just want to preside over a massacre. Tower defense games grant that wish, and usually in a cheery, non-threatening arena.
Nor is a tower defense game devoid of interesting decisions. It's just that those decisions aren't strategic so much as they are geometric. A tower defense game is about how you manage the positioning of your defenses and the flow of creeps. This may not require strategic decision-making abilities, but it does demand a proper reading of the map and the ability to plan ahead.
In a tower defense game, the player has to create killzones and maximize the amount of damage inflicted there, but avoid creating a bottleneck where so many enemies will arrive at once that they overwhelm the defenses. There is also the problem of ensuring that the defenses work well against every type of creep, which typically have special properties and resistances that cause problems for the defender.
All of which means that a proper tower defense game is for the tinkerer rather than the strategist. Indeed, the biggest problem with the genre is that there is usually an optimal layout on a given map that guarantees victory. Once that layout is discovered, the map is finished because the results will never significantly change.
On the other hand, there's a great deal of pleasure to be had in making slight adjustments to a position and seeing how they impact the battlefield. This is a pleasure sadly to be found lacking in most real-time strategy titles, which are usually designed to punish defensive-minded players.
For instance, a game like Company of Heroes offers players a lot of options for setting up a static defense. Landmines, sandbag walls, barbed wire, and vehicle obstacles can all be employed, in conjunction with the player's arsenal, to block, channel, and slow an enemy's advance. However, CoH also moves at such a rapid clip that it rarely pays to set up a good defensive position, nor do most of the maps lend themselves to turtling. You might set up a great position around a fuel point, for instance, only to watch an enemy column bypass it entirely and hit two unguarded capture points. That's historically accurate, certainly, but still infuriating for the Maginots among us.
There's also a sound gameplay reason why static defenses typically get short shrift: they can ruin a game by raising the cost of attacking so much that the matches become grim sieges. Total Annihilation, for instance, had some of the best fortifications of any RTS I've ever played, but my games often broke the three hour mark without showing any promise of a conclusion. Between the punishing long and medium-range artillery, powerful short-range defensive emplacements, and battlefields that grew increasingly choked with wreckage from the prior battles, launching an attack was prohibitively expensive and difficult. TA came closer than any RTS I've ever seen to modeling the reality of warfare on the Western Front during the First World War, feelings of futility included. It made for incredible spectacle, but also endless back and forth.
The tower defense genre may not provide deep gameplay, and it does get old quickly, but it answers a particular craving that few games can accommodate. The reason so many novice players in a strategy game tend to fall back on defensive works is because stationary defenses offer the illusion of security and control, and if the enemy would just behave as expected, the illusion would be reality. In a tower defense game, victory really is that simple and certain.
Rob Zacny turtles because he is easily frightened. He is currently entrenched at http://www.1up.com/do/my1Up?publicUserId=5928939.
