Triple Queens

This is a Match-3 puzzle game that inspired by Triple Town. This game takes place on a fixed 6 x 6 board. Player will be given a random chess piece. When there are three or more identical chess pieces adjoin, they will be merged and promote to a more "senior" piece. e.g. 3 Pawns will forms a Knight. The most senior piece is of course the KING.

So, the objective of the game is to upgrade as many chess pieces on the board to KING as possible; There can be multiple KING on the board. And the game will end when all cell on the board are filled. The game comes with unlimited moves as well as undo feature.

The seniority is ranked from PAWN, KNIGHT, BISHOP, ROOK, QUEEN to KING.