This game is created with HTML, CSS and JavaScript and it generates a random number between 1 and 20, and the player has to guess the number by entering it into an input field and clicking a "Guess" button. If the player's guess is correct, a message is displayed congratulating them, and the input field and button are disabled. If the player's guess is incorrect, a message is displayed informing them of their mistake, and their score is reduced by 1. The player starts with a score of 20, and the game continues until the player guesses the correct number or their score reaches 0.