Apocalypse World is a genre-establishing tabletop RPG about post-apocalyptic life. It inspired a slew of other tabletop RPGs that use roughly similar systems but focus on wildly different themes and settings.
Such games are collectively known as Powered by the Apocalypse (PbtA) games, and their strength, as well as their weakness, is that they are each tightly focused on the themes that that particular system wants to tell. Apocalypse World, for example, is designed to be a gritty, realistic game where life is cheap and hard choices abound. You could try running it as a lighthearted exploratory romp, but the system would fight you at every step. Trying to make a generic version of PbtA games, therefore, would be the height of folly, discarding every advantage that PbtA games have in favor of something that appeals to nobody. ... Anyhow, here's a generic version of PbtA games. : ) Generic World core rules