Left4Dead week will feature one short piece on Left4Dead each day this week to celebrate the full release of the game.

The problem with the AI director is that I think the implementation works too well for zombies, and won’t be adaptable enough for anything else. The quiet, eerie moments of being unsure whether an area will be filled with mindless undead, crouched shivering in a corner, leaning helplessly against a wall or vomiting up raw chunks of flesh, or completely empty; the variation in threats from rushing hordes, against the lesser special zombies (boomer, smoker or hunter), the adrenal rush of fighting a tank or trying to creep past a witch.

Contrast this with Half-Life 2, where there is a similar variety in enemies, but all of which are pre-figured by the environment you are moving through: no mix of head crabs, combine and Ant Lions together would make as much sense. And the simplicity of the zombie AI will make it hard to have a similar flood, of say, Nazis en mass. Any more intelligence in the enemies than that which the zombies display would dilute the flood to a surge or trickle, as they found alternate routes, held back or hid within the level to wait for you. The techniques used by the ALife in S.T.A.L.K.E.R. makes more sense for the most games: where each enemy has a distinct personality and set of goals to move through large free roaming levels.