UNO is a popular card game that was first released in 1971. It is played with a deck of 108 cards, which are divided into four colors: red, green, blue, and yellow. The goal of the game is to be the first player to get rid of all their cards. Players take turns matching one of their cards with the card on the top of the discard pile, either by number or color. Special action cards add an element of strategy to the game.