From the introduction:
Three hundred years ago to this very day, the human galactic empire of a.d. 2492 encompassed 77 thriving worlds plus many small outposts scattered across the human part of the galaxy. The 77 Worlds supported each other and helped all humans expand into the galaxy.
The Lost 77 Worlds is a role-playing game with lots of differences. The game is set in a post-apocalyptic environment on Luna or on the Blasted Earth. Players use a deck of cards to enhance their role-playing experience. The draw of a heart strikes your enemy. Drawing a diamond allows you to figure out a complex ancient device. A high club allows you to do feats of dexterity. A spade draw defends you from damage in combat.
Characters adventure and gain ranks and abilities as they move from dome to dome. Eventually, they discover the means to leave the moon and explore Earth Prime - "The Blasted Earth." The core rulebook includes 9 character types and was developed to run initial adventures in a "west world" like Vacation Resort on Luna after the apocalypse on earth.