Millennium 2200 is a turn based post-apocalyptic game set in the Solar System. The people of Earth had been wiped out in a meteor collision, and only a handful of humans are alive, having been spared death by living on science outposts on the Moon and Mars. As the commander of the Moon base, you must try to find a way to keep your people alive and restore humanity to Earth and also colonize the planets and moons of the Solar System. In your way is the commander of the Mars base.
In Millennium 2200, you command the six key areas essential to the development of the Moon base: life support, energy, research, mining, defense, and production. Energy is necessary for the other five areas, while mining provides minerals used for producing ships, technology, and defenses. Life support refers to your base's population, and ships that need crews draw from this. Research and defense are self-explanatory.
The Moon can only offer so many types of material in so many amounts, so you must find other sources of minerals elsewhere. This can be done by sending Grazer-class ships to the asteroid belt to scan for and collect useful minerals, or by colonizing the planets or their principal moons that contain those minerals. The latter is more time- and resource-consuming, as you need to construct a colony base to send to the moon or planet, and then send a Carrack-class ship to the new colony to pick up the minerals mined there and deliver them to the Moon.
Before colonizing a planet or moon, you must first investigate it by having a probe land on it and then ordering your scientists to study the data and tell you whether it's worth colonizing. Once you finally manage to colonize the planet or moon, you'll also have to send power generators and fighters, as colonies cannot produce anything on their own, and the basic power generator they start with won't allow them to mine. Also, depending on the atmosphere of a colony, the colonists may mutate into different forms. Oxygenic and vacuous atmospheres won't cause mutations, but Nitrogenic or Sulphuric atmospheres will. The appearance of your colonists are shown.
As previously mentioned, the people of Mars don't like you, and they will often send fighters to attack the Moon and your colonies. If you have constructed fighters of your own, you can personally fend off the Martians. The battle sequence is very disappointing, and involves you moving crosshairs with your mouse over a lone 3D object and shooting it. These engagements only take a few seconds, and shooting the one object is somehow enough to destroy all of the attackers.
There isn't much else to Millennium 2200 other than colonizing planets and moons and fending off the Martians. The only real planning needed in the game is when to launch spacecraft, as the orbits of the planets and moons will determine how long it takes for a ship to reach its destination.
The graphics aren't bad (although Jupiter is green for some reason), however the sound effects are limited to odd MIDI beeps and buzzes. There is also no music in the game.