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I lost Saturday, Sunday and Monday to the cutest little game called Tower Defense. It completely mesmerized me for three days. I was told that during that period I hardly moved and there is no question that on Friday when I looked down to start playing it was morning, and when I again looked up, it was night. I haven’t been this engrossed in a game since Stronghold devoured weeks of my life back in 2002.

I found the game, which now is in version 1.5, on a web site called kongregate.com. Subsequently I found out that the game is available on a number of sites and that there is a thriving Tower Defense game community with their own web sites. Who knew?

The concept is simple: Kill moving creeps running through a rectangular box with blasts from stationary towers. The towers inflict damage on the increasingly virulent creeps as they run in two roughly symmetrical streams across a boxed field.  One stream of creeps originates from the top of the box, the other from the left, and they come in eight different forms with characteristics such as fast or slow, squiggly or tough.

The towers come in seven different forms and inflict different types of damage on the creeps, which change when the towers are combined by placing them in close proximity to each other. Some of the towers are more successful on certain types of creeps than others. You build towers by spending an initial bank of coin points which is replenished by creep kills. This makes the player focus on scarcity and choice while solving the 7^8 plus permutations of problems that unfold in the time dependent game (each wave of creeps begins its march at relentless intervals. This is at the core of the game’s mesmeric effect.)

When you lose – and you always lose – the game board is immediately blocked with a menu screen so you can’t examine the success of your tower configuration. This is a stroke of game design genius because you have to go back in and play again to test out your new ideas rather than examining the old, since you are not quite sure if that last tower, for example, was in the right place or not, and you can’t see exactly where it was anymore.

You would think that there was an optimal solution to the game but there is not. Your game-playing hubris is one of the first victims of the creep’s assault. Just to humble you the game incorporates subtle stochastic changes in the program applet which show up with greater impact as the game wears on. And isn’t that the shocker of all? This game is only an applet in a browser. What a marvel of design. I can remember when a game like this took all my PC’s computing gizmos to run, and those games weren’t nearly as much fun.

The game combines puzzle solving, strategy design, and a good dose of mouse skills to get a high score and avoid the embarrassment of a creep getting past your defenses. If they do get past, they taunt you with an annoying little cheer of “yippie!” as they escape your maze. (Such creeps!)

There are many different strategies to maximizing creep kill, and you soon learn that 100% mortality is the absolute minimum required, if you have any aspirations of a high score. If a single creep gets past, you not only loose one of your 20 lives, you also loose the coins that creep’s death would have represented and that you could have invested in the strength of your towers to defend against the next more powerful onslaught. I got to the point of restarting the game if even one creep escaped, because if one got by, you were done for.

Balance in the game is also critical. Neglecting air defense (yes, some creeps fly) in favor of a rock solid ground game, brings quick demise as a dozen soaring creeps appear and exit unscathed with that annoying “yippie!” (Those creeps!)

As the hours of game play begin to slip by you find yourself equating the game to actual business situations such as a start up, where over emphasis in one area leads to crippling deficiencies in others, and ultimately to Faustian tragic endings. Just as you start waxing philosophical, a squiggly creep spawns an offshoot that jumps your rocket wall and gets away. (That will teach you to day dream about reductionism. Creep!)

How high is a high score? The kongragate applet loads not only the game but also a chat room with high scores of the day, week and of all time from other players (don’t go there, it’s depressing). I felt great about my early scores of 400 – 500 until I learned that the lowest best score of the day was over 6,500, that 10,000 was not uncommon, and that there were hundreds of these scores. After three days I was stuck at 3,000 and I realized that in addition to a strategy game Tower Defense was also a giant mathematical optimization problem, one that had not yet been solved by me, but that had been solved by a whole bunch of middle school kids with way too much time on their hands.

As many strategies as there are, there are as many adamant defenders of each strategy. They fight it out on the many web sites devoted to the game. Once you and your friends start playing you will see communities and factions form in defense of various strategies. And people become religiously attached to these approaches. Maze vs fort, outer perimeter vs boomer squares. You would not believe the virulence that people’s arguments take on these topics. Which gets to a whole topic of viral spread and memes and other stuff. But I don’t have time for that right now. I have to go back in and try my new maze design. I‘ll be back in a few days…

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