In Nightfire there is a rocket launcher that fires homing missiles. These missiles follow their target until they hit a surface and explode. How they do this is based off the principle that warm bodies emit infrared light, therefore if a rocket were to follow infrared emissions it would most likely be following a body. Homing missiles are so effective that 90% of all US air force losses can be attributed to them. In order to change directions mid flight, it adjusts the direction of its rear thruster according to the direction the infrared light was received. This is done so quickly that the missile has smooth turns and adjusts its flight path at almost the same time its target does. In Nightfire, this creates a weapon that is pretty much unavoidable unless you disappear into a building or behind a safe wall.