Know your enemy.
This video is an interesting behind-the-scenes look into the capabilities and senses of each different enemy in the 1993 videogame DooM.
- Bonus content and nostalgia:
A look at where consumer available FPS began with Maze Wars+ (1987)
Maze Wars+ was the first experience of a networked-multiplayer-graphical-game for many people, and completely mindblowing for the era.
- For a current quality FPS experience, see Cube 2: Sauerbraten
Decino’s entire analysis series is great, he also makes the music for most of them.