Uridium is a science fiction side-scrolling shoot 'em up originally designed by Andrew Braybrook for the Commodore 64, and later ported to other 8-bit machines. It consists of fifteen levels, each named after a metal element, with the last level being called Uridium (a fictional metallic element, not to be confused with the real metallic element iridium). The manual quotes Robert Orchard, who invented the name as saying "I really thought it existed." Source: https://en.wikipedia.org/wiki/Uridium