ZERO21 SOLITAIRE: keep the number between 0 and 21

GAME INFO
Zero21 solitaire game, an online calculation game, with cards in which you add or subtract the numbers of the cards, and you have the goal of keeping the result between zero and 21. Add and subtract, practice basic calculation operations, to keep your number in that range. Choose the addition or subtraction card, depending on whether the number is positive or negative, and keep the final result within the minimum and maximum in this online solitaire and math game.