Tigers and Goats is a draw LIM YEW JIN AND JURG NIEVERGELT

Bagha Chal, or “Moving Tiger”, is an ancient Nepali board game also known as Tigers and Goats. We briefly describe the game, some of its characteristics, and the results obtained from an earlier computer analysis. As in some other games such as Merrill’s, play starts with a placement phase where 20 pieces are dropped on the board, followed by a sliding phase during which pieces move and may be captured. The endgame sliding phase had been analyzed exhaustively using retrograde analysis, yielding a database consisting of 88,260,972 positions, which are inequivalent under symmetry. The placement phase involves a search of 39 plies whose game tree complexity is estimated to be of the order 10. This search has now been completed with the help of various optimization techniques. The two main ones are: confronting a heuristic player with an optimal opponent, thus cutting the search depth in half; and constructing a database of positions halfway down the search tree whose game-theoretic value is determined exhaustively. The result of this search is that Tigers and Goats is a draw if played optimally.