The contents of a card game involves one or more decks of cards. The number cards of two through 10 are usually worth their face value (i. e. the two card is worth two points, the three is three points, etc.), the Ace is usually worth one or 11 points, and the King, Queen, and Jack cards are usually worth 10 each.
The only card games for the Vectrex are Vector 21, Royal 21 (along with their companion limited editions), and Hexed!.