Challenging, Uno Wiki

Challenging is the act of questioning whether a player played a Wild Draw Four card illegally. The official Uno rules state that a Wild Draw Four may only be played if the player who played it does not have any cards matching the color of the card at the top of the Discard Pile. Therefore, any time a Draw Four card is played, the player who is next in line may choose to initiate a "challenge" to see if the card was played illegally or not. If a challenge is initiated, the player who played the D

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