What Chess'Extra puts on the board
Chess'Extra is a free chess variant played on a 10x10 board instead of the usual 8x8, and it adds two pieces you won't find in standard chess: the Priest and the Assassin. The store text spells out how they behave: the Assassin has its own moves and captures, and the Priest has its own moves and captures as well. One rule worth knowing before you sit down is that when a Pawn is captured by a Priest, that Pawn is converted to the Priest's color and placed on the square the Priest occupied before moving. So a Priest can flip a small piece to your side rather than simply removing it from the board. Basic Chess is also available if you'd rather stick to the familiar rules on the larger board.
Extra modes to shake up a match
Beyond plain chess, four additional modes change how a game plays out: Traps, Reinforcements, Fog of war, and Random positions. Fog of war hides part of the board until you can see it, Random positions starts you with an unexpected setup, and Traps and Reinforcements add their own wrinkles to the board. Since these are modes rather than separate games, a group can agree on one rule set and run a series of matches with it, or rotate through the modes so nobody gets bored of the same layout. Everything is turn-based, so there's no time pressure — you can talk through moves and take your time.
Playing together and getting started
You can play against the AI, play against yourself, or create and join a lobby to face other players, with online PvP available for matches over the internet. Local multiplayer is listed as a feature too, so a group sharing one screen can take turns at the board. Winning games against the AI or an opponent earns money, which you spend to unlock customized boards and colors for your pieces — a handy goal if your group wants something to work toward across sessions.
Before starting, check which mode everyone wants, since the Priest and Assassin rules and the four extra modes all sit on top of the standard chess you may already know. The 10x10 board gives pieces more room to move, and the Priest's conversion rule means a lost Pawn can come back on the other side, so watch your back rank.