Krypto is also the name of a mathematical
card game. It is played with a
deck of 52 cards which consists of 3 each of the numbers 1 through 10, 2 each of 11 through 17, and one each of 11 through 25.
There are several variations, but the basic idea is that each player is trying to form a certain goal number (the number on a randomly-selected card visible to all players) by arranging the numbers on 5 other cards in some order, and placing mathematical operations (+, -, x, and /, and parentheses for grouping) between them, and to do it before any of the other players do.