ZX Spectrum game

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Okay, I'm trying to remember the name of an old ZX Spectrum game. The game was something along these lines: You were in control of an outpost on a planet/moon which was under attack by alien ships. You had different views of the base which you could switch between. The base had different buildings. You could get supplies by teleport beam or something. The spinning UFOs would either drop bombs on your base, or drop infiltrators. You had to control a security robot in the connecting tunnel to destroy the infiltrators. You could also shoot the aliens down. I think you also had to repair the base. Any ideas what game it was?