Stop is a variation of Uno, with players trying to empty their hand of cards by playing onto a discard pile by matching the color or number of the card on top of the pile. Stop also includes a few special cards and rules to tweak the gameplay and differentiate it:
6s and 9s are considered to be identical, so a 6 can be played on a 9 regardless of the color and vice versa.
If a player has a number card identical in color to the top card, she may play it out of turn onto the discard stack.
An exchange card allows the player playing it to have everyone give their cards to their left- or right-hand neighbor.
The +X card forces the next player to draw the top card of the deck and add it to her hand. If it's a number card, she must also draw that many cards.
The +2 card forces the next player to draw two cards and skip her turn – unless she also plays a +2 in which case the next player must draw four cards, etc.
A skip card skips the next player.
A stop card, which is numbered 0, can prevent the action of an exchange, +X, +2 or skip card played by the previous player.
When a player runs out of cards, the other players score points based on the cards they still have in hand. After multiple rounds, the game ends if a player has 500 or more points; the player with the fewest points wins!