Cinderella's Dance was first released under the name Count Up 21 at a January 2019 event called "これはトリテなのか？" ("Is This a Trick-Taking Game?"). This two-player game may or may not be a trick-taking game, and is, in a sense, intended to live on the edge.
The game consists of a deck of cards (numbered 1-21) and two optional scoring cards. To set up a round, shuffle the cards, remove five from play, then deal each player eight cards. The starting player plays any card, then the next player either plays a card at most three higher than the previous card — so on a play of 5, the next player could play 6, 7, or 8 — or passes. When a player passes, the previous player collects the played cards, stacks them as a scored trick, then leads a card. When a player is out of cards, you resolve the current trick, then the player who has collected more tricks wins the round; in case of a tie, the player who collected the last trick wins.
The first player to win three rounds wins the game.