Freespace 2

Freespace 2 impressed me with its idea and execution. An infinite universe from which enemies swarm near the ground, and it's up to you to neutralize the enemy. You find yourself in the cockpit of a warship spacecraft, equipped with several weapons with which you must defeat the enemy. Freespace 2 offers several missions with multiple aircraft in a darkened universe.

In 2002, Volition, Inc. released the source code for the game, allowing the community to modify the game and create new content for it.