Under the Broken Moon (2002)

Subtitle: The Thundarr the Barbarian Role-Playing Game

From the Introduction:

"The year 1994. From out of space comes a runaway planet, hurtling between the Earth and the Moon, unleashing cosmic destruction. Man's civilization is cast in ruin. Two thousand years later, Earth is reborn... A strange new world rises from the old: a world of savagery, super science, and sorcery. But one man bursts his bonds to fight for justice! With his companions Ookla the Mok and Princess Ariel, he pits his strength, his courage, and his fabulous Sunsword against the forces of evil. He is Thundarr, the Barbarian!"

The world of 3994 is a pretty damned primitive place. Other than the wizards and their war machines, the population of the Earth is reduced to subsisting off whatever debris is still around 2000 years after cosmic destruction cast civilization into ruins. Which brings up a good point: just how did all this stuff survive 2000 years, anyway? ...

Game mechanics adapted from the 1992 edition of Over the Edge™ (Jonathan Tweet, Robin D. Laws) by Brandon Blackmoor. Over the Edge is a great game by Atlas Games, and you should buy a copy.

This game exists in HTML format (web page), see links section.