Inspired by classic two-player card games like Gin Rummy and Koi-Koi, in Heavenly Bodies players meld three or more cards in sets and runs, aiming to pass thresholds for each suit in order to score points. Each turn, players may either draw two cards from a shared deck, then discard a card to either of two discard piles OR draw all the cards of either discard pile, melding any that they can into sets, then taking the remaining as penalty cards. Once players have melded cards, with the number of cards depending on the suit, they score points. Each suit in the game — planet, moon, comet, and star — has a different composition of ranks based on a pyramid, and card thresholds worth different amounts of points. Each hand is a race to 5 points. Once a player reaches 5 points, they can stop the current hand and collect one star fragment OR "Nova" and push their luck to reach 10 points before their opponent reaches 5. If they Nova successfully, they collect two star fragments; if not, their opponent collect one star fragment instead. Whoever collects four star fragments first wins.
