The Particle System
The particle system for Outpost is exactly like the one from Chapter 13, "Playing God: Basic Physics Modeling." Particles can be created with various velocities and colors, and there are functions to create sets of particles with specific properties to mimic explosions and so forth. The important thing is not how particles work (because you already know), but how I used them.
Particles are used for a lot of things in Outpost. I want all the enemies to leave vapor trails when damaged. I want the player to leave plasma behind when flying around. And when something is damaged or blown up, I want a lot of particles to be part of the explosion in addition to the bitmap-animated explosions.
The cool thing about particles is that they're so cheap and add so much to the visual excitement of a game. Not to mention that vapor trails and particles can be used as game elements themselves for tracking, or for other interpretations: food, footprints, whatever.