UNO is a popular card game that is played with a specially printed deck. The game is designed for 2 to 10 players and involves matching cards by color or number. The objective is to be the first player to get rid of all your cards. Players take turns drawing cards and playing them, while also using special action cards to change the game dynamics. Each player starts with seven cards, and when they have only one card left, they must shout "UNO!" to alert others. If another player catches them not saying "UNO," they must draw two additional cards as a penalty. The game continues until one player reaches a predetermined number of points, usually by accumulating points from the cards left in opponents' hands.