X-COM: Terror from the Deep

X-COM: Terror from the Deep was MicroProse's 1995 sequel to the landmark UFO: Enemy Unknown, and it kept the acclaimed formula almost entirely intact while relocating the war beneath the waves. Set decades after the first alien invasion, the story picks up as a long-dormant alien threat awakens in the oceans, and you once again command the secretive X-COM organisation, now battling aquatic terrors from underwater bases and submersible craft.

The two-layer structure that made the original so compelling returns. On the strategic Geoscape you manage funding, research, manufacturing, and the interception of enemy craft, while the tactical battles play out on turn-based, isometric maps where every soldier's action points, line of sight, and nerve matter. Terror missions, ship assaults, and base defences all carry the same knife-edge tension, where a single careless move can cost you veterans you have painstakingly levelled up. The research tree, rebuilt around alien biology and technology of the deep, rewards methodical play.

The game is notorious for being harder than its predecessor, with two-stage missions and a brutal difficulty curve that can overwhelm newcomers. It also reuses the first game's engine closely enough that some see it as more of an expansion than a true sequel. Even so, more of one of the greatest strategy games ever made is hardly a bad thing, and Terror from the Deep remains a deep, atmospheric, and punishing classic.