UFO: Alien Takeover for OpenXcom is a total conversion mod that enhances the original game with a wealth of new content, focusing on strategy horror gameplay. It introduces various new items, weapons, aliens, missions, and an expanded narrative that challenges players to make tactical decisions in a resource-scarce environment. The mod emphasizes a slow build-up of power, starting players off with basic melee weapons before gradually introducing more advanced armaments as they progress.

Designed primarily for experienced players, this mod offers a challenging experience, with many features aimed at increasing difficulty. Players can utilize an 'Adjusted Difficulty Mode' to make the game more accessible, providing options for those who may find the standard mode too daunting. The game encourages strategic planning and resource management, making each victory feel rewarding. Additionally, players can explore new operations and tactics, further enhancing the gameplay experience.