"Congratulations on your recent promotion and good luck in the upcoming battle. In the past we were invaded from other worlds but now, in 2084, the Aliens are travelling from another dimension. The means by which they achieve trans-dimensional travel is unclear, but it is apparent that the UFOs use some form of Dimensional Gateway. The gateways can appear anywhere in Mega-Primus. We would advise beginning the research of Dimension Gates immediately.

You have at your disposal the finest technology Mega-Primus has to offer to combat the Alien menace. Your Agents will be responsible for investigating any strange events that might reveal Alien activity.

The objective of these investigations is to gather as much information about the Aliens and their technology as possible. To defend Mega-Primus effectively, you will be responsible for research and development based on the results of these investigations.

X-COM must recover all Alien artifacts and technology from Alien encounters, in order to research and develop new weapons and craft. The results of your investigations will be published in the UFOpaedia, so that both you and your Agents have the most up-to-date information. Without this information we will not know of the Aliens’ intent or, more importantly, a means by which we can defeat them.

X-COM should retain a covert status as it monitors the situation in the city. Our investigation is secretly funded by the Senate and without this funding, the effectiveness and scope of operations will be severely diminished.

The success of our operation depends on your efforts. The safety of Mega-Primus is in your hands; your task is to command X-COM’s forces to defeat the Alien incursion!"

In the fourth installment of the series, we return to the squad-based strategy gaming style of play set out in the first two titles, but with much improved gameplay and graphics, even if the colours are a little bright in places.

Also for the first time, the game is set in the city of Mega Primus rather than encompassing the entire earth, as a totally new set of alien creatures invades from a completely different dimension.

Whilst Apocalypse does bring with it some revolutionary new features, such as the option for real-time gamepay as well as the traditional turn-based, it was rushed to completion and unfortunately certain features were cut from the final game, as can be seen on the Concepts, Buildings and Weapons pages on the Apocalype menu to the left.

There's a few editors and mods to check out in the files section and the Rookie's Guide is also worth a read if you didn't get the original boxed version when it was released.