Memorize game from stanford swiftUI course
Game starts with a random theme. There are 5 themes included: "Halloween", "X-mas", "Birthday", "Easter" and "School". Each time game started with random number of pairs (between 2 and 5).
Button "New game" will start a new game with a random theme.
Rules for scores: +2 if cards matched, -1 for each card that was already opened before.