X-COM: UFO Defense is based on the 1994 PC game originally developed by Mythos Games Ltd. The player assumes control of the X-COM task force, building bases and tracking various UFOs on a 3D map of Earth. Once a UFO is spotted (represented by a red cross), you must try to intercept it so that it crashes over dry land. You'll then need to send your heavily armed squad to the site, where you'll witness the downed craft and surrounding terrain from an isometric perspective.
Moving your troops is accomplished through a point-and-click interface with each side alternating turns. Your three goals are to (1) engage the aliens face to face, (2) either stun or kill them, and (3) retrieve whatever technology or weapons you find so your scientists can replicate them. After all, you have to fight fire with fire! The PlayStation version supports both the mouse and memory card, with the latter allowing you to save the game at any point (as long as you have five blocks free).