UNO FLIP plays like regular UNO, except there are two sides to the deck of cards: a "light" side and a "dark" side.
You start playing with the Light Side, but whenever someone plays a FLIP card, the deck is flipped over (as are the cards in your hand) and now everyone must play off of the Dark Side of the cards.
The Dark Side has different Action Cards with much stiffer penalties. Player's must play with the Dark Side cards until someone else plays another FLIP card, and then play goes back to the Light Side, and so on until someone has played all the cards in their hand, ending the round.
As always, if you are the first player to get rid of all of your cards in a round, you score points for the cards your opponents are left holding. Points in rounds accumulate and the first player to reach 500 points wins.