Mongolian Blackjack

The essence of the game: Two cards are dealt to each person. One of your opponent's cards will not be visible to you. Your goal is to score 21 points. You may draw more cards or stop at once. Points are measured according to the strength of the card.
Card Strengths: Jack, Queen, King - 10 points Ace - 1 or 11 points 2 to 10 - 2 to 10 points.
Winning conditions: The first person to score 21 points wins. It is necessary to score as many points as possible, but not more than 21. In case someone scored more than 21 points, he loses. In case someone took a card, but the opponent still has more points, he loses.