From the website:
"Alien Checkers is a versatile game. Besides using cards during the game, players select one of nine special cards to secretly find out which planet they are representing: each planet has a different secret victory condition. Children can enjoy how the game is silly and (compared to plain checkers) gives them a better chance of winning when playing their parents. Adults who wish to analyze the game more carefully will notice new flavors of strategy as the cards and secret goals work together."