I’ve previously written about my little World of Warcraft problem, which cost me a summer. My latest, greatest productivity killer is called Tower Defense.

It’s not one game really, but rather a genre of videogames in which the objective is to place and upgrade a series of automated kill-bots (towers) in order to obliterate wave after wave of bad guys (creeps). The latest incarnations are all Flash-based, which is uniquely insidious. Normal videogames can be wiped from your hard drive; these games are always just a click away in your browser.

The best Tower Defense games are made by Paul and Dave, who recently quit their “day” jobs to devote themselves to ruining productivity on a full-time basis. Dave’s Vector TD is free for the cost of a Orbit gum commercial, and is fairly classic, with a series of maps that constrict the creeps’ path (and limit tower placement). Paul’s Desktop TD is a good example of the “mazing” or “freeform” variety: on a blank field, you use towers to herd and direct the creeps to their death. It’s crazily popular because it offers the illusion of optimization. It seems like there should be one ideal map, which keeps you playing and testing — and going back to the discussion boards. But any small change in the underlying variables would ruin the winning strategy.

The genre isn’t new by any means. Starcraft introduced the Protoss Cannon — generally the cheesiest way to win any fight — while Warcraft III’s development system led to a lot of good Tower Defense games. Flash Element Tower Defense is probably the closest incarnation.

Why do I bring up Tower Defense, other than to derail other screenwriters’ productivity?

Well, it occurred to me, “What would the movie version of Tower Defense be like?” Is it a castle siege movie? An Aliens movie? A zombie thriller? And then it struck me.

It’s 300.

You have wave after wave of differently-styled Persians channeled through a narrow opening, no consideration to their lives. You have the towering Spartans, who simply defend their position and watch the bodies (literally) pile up. Just like in Tower Defense, the big worry is whether there will be a leak. From the beginning, you know eventually the defense will fail. The creeps will win; it’s just a matter of when.

This isn’t a slam on the movie, really. 300 knew what it was doing, and did it admirably. But watching it, I kind of felt like the guy invited over to check out the latest XBox game on the big screen, only to find his friends unwilling to give up the controllers. It was still exciting, but not quite the experience I’d wanted.

In terms of videogame addiction, Tower Defense is a lot less dangerous than WoW. For starters, there’s a “pause” button, so it’s possible to answer the phone. It’s also short. A game is five or ten minutes. The open-endedness of WoW is what’s cost people their careers. Tower Defense is like a twitchy Mine Sweeper, or Sudoku without the false sense of being good for you. It’s a time suck, though, which is part of why I’m writing about it. Having explained it, I probably won’t want to play it as much.

Probably.