A collection of some old, but great, text-only computer games. My favorites are Hamurabi and Super Star Trek.

Hamurabi is a crude simulation of an ancient city-state, Sumer. You allocate bushels of grain to plant and grow more, feed to your people, and buy more land. It's challenging, but can get addicting. An interseting story behind it is that the real name of the city's ruler is Hammurabi, but the second 'm' was dropped when the game was put into David Ahl's book of BASIC computer games, in order to limit the name to 8 characters. (BASIC is an old programming language.)

Super Star Trek is, like Hamurabi, famous, though not to the same extent. You take control of the USS Enterprise, traversing the galaxy on a mission to destroy the Klingon ships that menace the Federation. Every game has randomized locations of stars, starbases, and Klingons; number of stardates until the Federation is conquered, unless you defeat the Klingons; and number of Klingons. You can control the amount of energy available to shields and phasers in battle, as well as firing photon torpedoes that destroy Klingon ships in one hit, as long as your defined trajectory doesn't make it miss. Captain Kirk's crew even talks to you, responding to your orders. It's a really cool game, and you can be playing it for long stretches of time without even realizing it. Though I prefer this version, a more complicated version with Romulans, supernovae, and automatic trajectory calculation, among other features, can be found here.

The rest of the games are pretty great, too. Just because they don't have graphics, it doesn't mean they can't be good!