A Boy and His Tank (New Kashubia, #1)

The planet New Kashubia started out as a gas giant, but when its sun went dupernova, lighter elements were blasted into space. All that was left was a ball of heavy metals, heated to 8,000 degrees. As it colled, tungsten solidified first at the survace, and layers of other metals continued down to a ball of mercury at the center. The sun meanwhile evolved into a pulsar with a deadly beam of radiation that baked the planet's survace. The New Kashubians lived inside the planet, in tunnels drilled in a thousand foot thick layer of solid gold. Still without carbon, oxygen, hydrogen, or even dirt, the colonists were the poorest people in the universe. But when they combined virtual reality with tank warfare, giving their warriors symbiosis with their intelligent tanks, neither war nor the galaxy would ever be the same. Not to mention sex... The poorest people in the universe, the inhabitants of New Kashubia live underground in tunnels drilled through a thousand feet of solid gold, but things change when the New Kashubians combine virtual reality with tank warfare to give their warriors a symbiotic relationship with their intelligent tanks. Reprint.