In this play, which may have been from a Ray Bradbury or Dimension X show, robots protect humans from an alien invasion. The aliens kill off most of humanity. It gets to the point where only two humans remain and live in a cave, protected by robots. However, eventually they die too. The robots create an engine which spawns a sentient being which shoots up into the sky and kills all the alien ships. The soundtrack seemed to have lots of whirring and clicking sounds, with sparks going off. I'd love to find out what this was as it was quite unique.