The Initial Deal
Each player starts with 13 cards from a standard 52-card deck, leaving 26 cards in the stock. Spades Duel on this site uses this draw-after-each-trick format. It is different from two-player variants where players select or discard cards before play.
Drawing After a Trick
A trick contains two cards, one from each player. While the stock remains, the winner draws first and the other player draws second. Both hands return to 13 cards after the draw. The 26-card stock therefore lasts for the first 13 tricks. Winning changes who leads next, but it does not let you choose the next card in the stock.
How Many Tricks Are Played?
After the stock is empty, the players finish the 13 cards still in their hands without drawing. A complete deal has 26 two-card tricks in total: 13 with replenishment and 13 without. Keep the stock phase in mind when bidding, because your initial 13 cards are not all the cards you will play.