In Cat in the Box: Deluxe Edition, cards only have numbers (1–5 for 2 players, 1–6 for 3, 1–8 for 4, 1–9 for 5), with five identical copies of each number. A card’s color (Red, Blue, Yellow, or Green) is determined only when you observe (play) it onto the central Research Board.
At the start of each round, every player sets aside 1 card face-down. In 2-player games, 3 of the 5 undealt cards are observed on the Research Board (placed in Green, then Yellow, then Blue) and predictions are skipped. In 3–5 player games, each player predicts how many tricks they will win (1, 3, or 4 in 3-player; 1, 2, or 3 in 4–5 player).
To play a card number and declare a color, that (Color, Number) space on the Research Board must be empty and that color must still be available on your player board.
Leading: The trick leader may not lead Red (Trump) until at least one Red card has been observed on the Research Board, unless they have no legal non-Red play.
Following: You may declare any available color with an empty space for your card’s number. However, if you declare a color different from the led color, you immediately forfeit the led color (marked with ✕) for the rest of the round.
Winning a trick: The highest Red card wins; if no Red card was played, the highest card of the led color wins.
Play continues until everyone has 1 card left in hand (8 tricks in 2–4p, 7 tricks in 5p) or a player has no legal (Color, Number) play on their turn, triggering a Paradox that immediately cancels the current trick and ends the round.
Non-paradox players score +1 point per trick won. If they matched their prediction (or won 4 or fewer tricks in 2-player), they also earn +1 bonus point per token in their largest orthogonally connected group of their own tokens on the Research Board. A player who triggers a Paradox scores −1 point per trick won and no bonus.