Sloop — released in Germany as Quanto — uses gameplay similar to that of Casino and Scopa with players trying to use numbered cards in hand to claim cards available on the table, but the game includes a few twists.

To start, the deck includes 122 cards, ten copies each of cards numbered 1-12 (with one rainbow card of each number) as well as two jokers. (Quanto has 110 cards, with one copy less of each card.) Each player starts with a hand of four cards, and four cards are laid face up on the table. On a turn, a player takes one of three actions:

Lay down one card, then collect all cards of the same number (including the one played) and two or more cards that sum to this number, placing all of these cards in a personal score pile.
Create a "build" (a.k.a. "Quanto") by laying down a card, taking one other card from the display, placing them to your side, then taking the matching number tile to mark this build; you can take two or more cards at the same time that sum to this value and place them in your build. In the future, you can play a card of this value to possibly add more cards to the build, then move all of these cards to your score pile.
Discard a card to the face up display. If you discard a 1, each opponent must give you a card from her score pile; if you discard a 2, you play a second card from your hand, once again taking any of the three actions; if you discard a 3, you reveal three cards from the deck, use one to perform an action, then discard the other two.

After taking an action, you refill the face-up display to four cards and your hand to four cards. If you use a rainbow card for action 1, you can claim another face-up card of your choice; if you use one for action 3, then you add an additional card to the display.

When the deck runs out and all players have emptied their hands, the game ends and whoever has the most cards wins.

Sloop includes partnership rules that allow partners to add to (but not claim) one another's builds and to swap cards with one another during play.