Rules of play from the back of the box:
HOW TO PLAY SPACE 1999 - A game for 2 or more players
Deal all the cards face down to the players. The dealer puts down any card in front of him, and the next player has to put down a card with the same symbol (the symbols are stars, moons, chequers and planets) or the same picture. If he cannot play any card, play passes to the next player. However, if he holds a switch card, he can play that, and he may then switch play to any symbol he chooses. The next player must then play a card with the symbol he has called. The winner is the first player to put down all his cards.
Note: There are separate game pages for the 1976 board game from Milton Bradley and the 1974 board game from Omnia, as well as the Italian game Spazio: 1999.