Abstract card game where you collect sets of three or more cards. Each card contains one to six abstract shapes, such as a green circle or a blue triangle. A set is called a "zero sum" if it contains an even number (including 0) of every shape. In the Seven Card Challenge, seven cards are dealt face up. The first player to find a zero sum takes those cards, which are replaced with new cards. When the deck runs out, the player with the most cards wins.