I&#x27;d suggest a slight change. Code all the pawns into 2 &#x27;pieces&#x27; and have a special piece for promoting. The 16 moves for the special piece can be an index from a list of possible promotions which is easier to generate and canonicalise than the total move list. This frees up 5 pieces for promoted queens. You could special case the king into the spare entropy in the rooks and bishops to save one more piece.