Number Nightmare challenges players to perform mathematical operations quickly. Numbered chits are randomly placed on an 8x8 board. Players score points by finding three numbers in a row vertically, horizontally or diagonally which, when applying any mathematical operations, produces the target number.

If the player cannot find a solution within the alloted time, the first player to offer a solution steals the point.

This game is included in Mensa Brain Games. Included in the box is a book of over 100 brain teasers, plus rules and components for 10 board, dice and word games.