Like so many other machine language programs from ANALOG, it was usually a decent clone of an existing commercial or arcade product. In this case, of course, it's Tempest (which, for some unknown reason, never saw the light of day as a home conversion). This game does give you pretty much the feel of Tempest, although it's not as frenetic and sometimes the guys don't seem to get killed when you shoot at them, thus causing your own demise. I think this is more of the result of vector-based games being poor conversion candidates for home play. For instance, Star Wars and BattleZone were two great arcade games that looked and played very poorly on the 8-bit.