To start the game you arrange twelve UFO cards face up in a circle, with a Planet card inside it. UFO cards are divided in colors and have numbers on them.
The aim of the game is to play UFO cards from your hand in order to win the cards composing the circle. The cards you take score points.
A card played from the hand can be played only on the UFO card in the circle next to the Planet card. Playing a card gives you the possibility of moving the Planet card accordingly to the value of the card played.
UFO cards are played one at a time and the effect produced by each card is resolved before another card can be played (this gives you the possibility of building a strategy).
A card from the circle can be taken only by cards of the same color. Different colors simply take the place of the card on the table.
Simple math can be a valuable asset in sorting out a strategy.