From the box: "Fast and Fun Number Crunch'n! Players add, or subtract, 1, 2, or 3 to the number the top card on the pile to determine if they have a card that can be played next. Sounds simple, but with everyone playing simultaneously, the options are constantly changing."
Part of Out of the Box's Fun to Go series, the tin contains 73 cards. Each has a large yellow number (1-10) and a small one in the corner indicating +/- 1, 2 or 3. A card is laid to start the central pile, then the rest of the cards are dealt out. Players race to add the next card to the center pile. As an example, a card with a large yellow 5 and a 2 in its corner could be covered by a 3 or a 7 card (which is 5, plus or minus 2). The first player to get rid of all their cards is the winner.