In The Enigma of Leonardo, players try to collect keys by creating patterns in the cards before them on the table.
To start the game, deal each player ten cards. Each player takes five of these cards at random, places them in a + pattern, then turns them face-up; the other five cards form that player's hand. Each card has two of twelve symbols in the upper-left corner.
On a turn, a player replaces one card in his + with a card from his hand, moving the first card into the + of his left-hand opponent in the same location; that opponent discards the card that was in that location. If a player creates a horizontal or vertical line of cards which each feature the same symbol, that player takes a key card showing that symbol. (A player can claim a particular type of key only once.) If all five cards in a player's + show the same symbol, the player can claim any key card that he does not already have. The first player to collect seven key cards wins.
The Enigma of Leonardo includes rule variants featuring additional ways to play.