Master of Orion II (MOO2) is one of the premier empire-building computer games, and it can be played by one or multiple players. It's a turn-based strategy game (TBS), which allows players plenty of time to plot and carry out really complex strategies.
Here's how the game works: You set up colonies on planets, grow their populations, and put them to work making weapons or defenses and producing food for other colonies. MOO2 lets you expand through a treacherous universe, colonizing, building and fighting when you have to. To win, you'll need to develop new technologies to support growth and defeat your enemies.
The most mind-bending aspect of MOO2 is the combination of grand objectives -- the control of the entire universe -- with the very detailed management of each facet of your empire. Another fascinating angle is that you will need to form diplomatic alliances with other races in order to further your goals.
Turn-based games are not as popular as they once were -- MOO2 was introduced in 1996 [source: Ward]. But the game, which spawned many other science-fiction exploration games, is still considered by many to be a fun and challenging adventure.