The volatile crust of the planet Y00l would be constantly erupting into fantastic shapes, if not for the crushing gravity that keeps the surface nearly table-flat over the entire planet. Even if there were elevation to speak of, the luminous inhabitants would be unable to climb a slope–and anything resembling a fall would be instantly fatal.
Once a planetary revolution, on the shortest day of the year, something wondrous happens: in small, localized pockets, for some reason, the gravity all but vanishes. The soil immediately leaps into the air, forming trunks and branches that would be otherwise impossible. The inhabitants flock to these spots, eagerly climbing the twisting shapes and for one short, glorious night enjoying the sensation of “up.”