X-COM: Terror from the Deep is the follow-up to the successful resource management and tactical combat game <a href=/info?28>X-COM: UFO Defense</a>.<br><br> 40 years have passed since X-COM defeated the aliens. But now, in the year of 2040, aliens begin to appear on the Earth again. This time the threat to humanity is coming from the depths of oceans. <br><br> Terror from the Deep is almost identical to the <a href=/info?28>original X-COM game</a>. The user interface, weapons, and aliens are all the same. The only difference is the adaptation of the aliens and weapons to the ocean environment. The game features both undersea and onland missions, and is significantly harder than its predecessor.