Facebook Messenger is good for more than just sending your friends silly cat stickers and emojis. By typing “@fbchess play” into the chat window, users can challenge any of their Facebook friends to a game of digital chess. The hidden chess game harkens back to an earlier technological era. Instead of dragging and dropping chess pieces as in most contemporary apps, players must use text commands to make their moves.

Though it’s a more laborious way of playing online chess than many of us might be accustomed to, the commands are somewhat intuitive. Once the game has started, players use traditional chess notation to move each piece. Users designate which piece they would like to move by typing K, Q, B, N, R, or P, which stand for king, queen, bishop, knight, rook, and pawn, respectively. They can also designate where they would like to move that piece by typing in the name of the new location. For instance, typing “@fbchess Pf3” at the start of the game would move White's pawn (P) forward one space, to square F3. Confused players can also access instructions by typing “@fbchess help" or check out the full list of chess commands on Life Hacker.

It’s unclear exactly how long the secret chess game has been around, but it has existed for at least a couple months. The Verge notes that reddit users on /r/chess first discovered the game last December. While the Facebook chess game might not be the most sophisticated chess app, it’s certainly a fun little Easter Egg and a useful way for newer players to familiarize themselves with chess notation.

[h/t The Verge]