Left 4 Dead: New AI Perspectives

Yesterday I downloaded the Left 4 Dead Demo off of steam and played through co-op with a couple of friends. The current server situation left things a bit rocky (I'm sure Valve will iron things out and more and more servers will be created later), but once we started playing, we were blown away. I couldn't believe how enjoyable it was to play the same two levels over and over again. But why was it that everything was so enjoyable?

Anyone who has been following Left 4 Dead over the last few months or so would know about its "Director". The Director is basically a server-side program that monitors the progress of the players and adjusts level difficulty, "infected" placement, and item distribution according to how well things are going. The better you do, the more zombie action the game throws at you. This creates a completely dynamic experience each time a level is played, keeping things from getting boring.

The elements the director employs are relatively familiar. One of these things is use of on-screen effects and music to create dramatic moments when the game gets tough. This is done quite well in most FPS titles these days, but often times these elements are only triggered by a specific location on a map, or a critical event. Having these things become dynamic, though, keeps gameplay fresh and enjoyable.

This aside, as enjoyable changing gameplay can be, I would go so far as to say that it can go too far. Valve's "Director" and AI system are impressive, and well-implemented, but only because they didn't take too many steps in that direction. One such a step is in level design. Some games rely on a type of pseudo-random process that creates dynamic levels for players to interact in. While this worked out well for RPG hack and slash titles like the Diablo series, it didn't work out as well in the Flagship Studios title "Hellgate London". But why? The answer, in my opinion, is that this kind of approach does not lend itself well to the 3D worlds we are used to in first person shooters. Dynamically created levels may hold a certain level of novelty, but follow a distinguishable pattern that quickly makes them feel worn-out. What's worse, level design is an afterthought, and one that is handled by a program that is often unable to create moments of intense strategic reaction, or thought-provoking problem solving.

The Left 4 Dead Demo levels were pretty well designed. Valve took into account a lot of the elements that make fighting zombies an intense and frightening experience and incorporated them into their maps. Often times you'll find yourself in a space where zombies flood in from all directions, or where a zombie lurks in a corner and you pass by without even noticing. This responsible level design approach coupled with the ever-changing zombie invasion of the Director takes the AI directed approach of game design to just the right level.

It seems clear to me that Valve has set a new standard in game design. A completely dynamic game experience is not very responsible and leaves too much of the game experience to chance. Future games without some kind of dynamic element, though, will probably feel lacking in light of Left 4 Dead's replay value. So perspectives in AI will likely be changing for the better, which is great, because I'm sick of predictable enemy placement!

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