Classic international chess. Timed, with a leaderboard for wins.
Checkmate your opponent's king — trap it so it's under attack and can't escape.
Pawn: forward one square (two on its first move), captures diagonally.
Rook: any distance in a straight line.
Bishop: any distance diagonally.
Knight: in an "L" shape — can jump over pieces.
Queen: any distance, straight or diagonal.
King: one square in any direction.
Castling: king and rook swap positions for safety, if neither has moved and the path is clear.
En passant: a special pawn capture just after an opponent's pawn moves two squares.
Promotion: a pawn reaching the far end becomes a Queen, Rook, Bishop, or Knight.
Control the center early. Don't move your queen out too soon. Keep your king safe — castle when you can.