X-COM: UFO Defense is a strategy game that combines tactical combat with base management and global defense. Players lead an international organization tasked with defending Earth from an alien invasion. The game unfolds on two levels: a global view where players manage resources, research alien technology, and intercept UFOs, and a tactical combat mode where squad-based battles occur. Players recruit and train soldiers, build bases, and develop new weapons and equipment based on recovered alien technology. Missions involve turn-based combat against aliens in various environments, with permadeath adding tension to each engagement. As the alien threat escalates, players must balance research, defense, and offensive operations to protect Earth's nations from panic and alien infiltration. X-COM: UFO Defense's blend of strategic depth, tactical combat, and atmospheric tension creates a compelling gameplay experience in the face of a global alien threat.