The aim of the game is to be the first player to score 500 points, achieved (usually over several rounds of play) by being the first to play all of one's own cards and scoring points for the cards still held by the other players.

Game consists of 108 cards: 25 in each of four color suits (red, yellow, green, blue), each suit consisting of one zero, two each of 1 through 9, and two each of the action cards "Skip", "Draw Two", and "Reverse". The deck also contains four "Wild" cards, four "Draw Four".

In the beginning, seven cards are dealt to each player
On a player's turn, they must do one of the following:

- play one card matching the discard in color, number, or symbol
- play a Wild card, or a Draw Four card
- draw the top card from the deck, and optionally play it if possible

Explanation of special cards:
- Skip card:
Next player in sequence misses a turn
- Reverse card:
Order of play switches directions (clockwise to counterclockwise, or vice versa)
- Draw Two (+2)
Next player in sequence draws two cards and misses a turn
- Wild
Player declares the next color to be matched (may be used on any turn even if the player has any card of matching color)
- Draw Four (+4)
Player declares the next color to be matched; next player in sequence draws four cards and misses a turn.

If a player does not call "Mau" before or slightly after laying down their penultimate card (double tap on your score) and is caught before the next player in sequence takes their turn (i.e., plays a card from their hand, draws from the deck, or touches the discard pile), they must draw two cards as a penalty. If you see that your rival has not called "Mau", double tap on their score and they will have to draw penalty cards.