Tower Defense

If Sid Meier's Alpha Centauri is the heroin of gameplay, the SMAC(k) if you will, then tower defense is the crystal meth. How appropriate then that some of the best games in the genre involve crystalline gems whose interrelated properties weave together in pyramidal symmetry just like the molecular structure of a jewel.

Gem TD has been out for a while; Gemcraft is just released. They both gripped me with euphoric insomnia, coupled with vitamin C depletion, grinding of teeth, and paranoid hallucinations of creeps, endlessly marching. Like all tower defense games, they evoke a superb linearity of thought, a simplified psychology of marching enemies, marching resources, marching upgrades, ever forward, ever higher. I can't belabor this meth analogy enough.

Immortal Defense puts you in the role of a man whose soul has been separated from his body and cast into higher dimensional space. There, you shoot things on a line, then achieve enlightenment.

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The "tower defense" genre arguably began with some scenarios in Warcraft, but has since become the first truly new genre we can point to as emerging from the indie games scene. Pioneered in Master of Defense, and widely available in free flash form in games like Desktop Tower Defense, a number of good commercial versions have appeared as well.

Games of this style seem to fall into two categories; ones, like Master of Defense, in which levels have different geographies and the main strategy is figuring out optimal placement for your towers; and ones like Desktop Tower Defense where the geography is open, and the main strategy is in building towers to channel the attackers (called "creeps") along a circuitous path, giving you plenty of opportunity to shoot at and kill them. Attack of the Creeps falls into the second category.

Desktop Tower Defense, designed by Paul Preece, is one of the brightest jewels in the fistful of free games that make up the Flash-powered land of the burgeoning tower defense category (think RTS lite here). While not the first in the field, it ranks among the best, with millions of games having been played since its introduction earlier this year.

Lock & Key is a tower defense game. With only one attacker wave. And it's in text.

The premise is that you're a dungeon designer, the one who lays out the arrangement of traps to keep in the extra-specially-dangerous prisoners. You've got a grid of rooms in which you can place these traps, and a limited budget to spend. When you're done, you're taken aside to a guard room with the King to watch as Boldo -- a kind of Tarzan figure gleaming with oiled muscles -- does his best to break out. If he fails, you win. If not, you get to watch Boldo defeating all the traps you so carefully laid out -- and the consequences for you are disastrous. Time to play again.

Defense is boring, right? Attacking is action, advance, and victory; defense is static. You sit there and hope for the best. No war was more boring than World War One--unmoving defensive trench lines for four long years. So a priori, you might think a game named "Master of Defense" would be, ah, less than scintillating.

Actually, it's quite cool.