From the campaign:
To play Flip Flash, players simultaneously flip through their cards, and race to play them on shared number piles in the center of the table. First card to the pile gets to stay!
You can play a number higher or a number lower than the top number on a pile at any time, only the color has to match. Of course if you play a WILD card, you can change everything about the pile to suit you, simply yell out the color and number you want the wild to represent.
When you have played all the cards in your down pile, you can yell "Flip Flash" to end the round. Scoring is +1 for every card played, and -2 for every card remaining in your down pile.
Play as many or as few rounds as you like! Each round is only about 5 minutes long!