This category would fit Metamorph Chess and Assimilation Chess, but there is a question of how finetuned our categories should get. On the one-hand, Diff-Promotion would fit in with Diff-Moving and Diff-Capturing. But then we still have games where there is demotion, or pieces change without involving promotion or demotion, such as when a player's own pieces merge or split apart. Should these be in a separate category, or should we have a category that includes promotion, demotion, and other ways of changing pieces? Maybe something like ProteanPieces.
This category would fit Metamorph Chess and Assimilation Chess, but there is a question of how finetuned our categories should get. On the one-hand, Diff-Promotion would fit in with Diff-Moving and Diff-Capturing. But then we still have games where there is demotion, or pieces change without involving promotion or demotion, such as when a player's own pieces merge or split apart. Should these be in a separate category, or should we have a category that includes promotion, demotion, and other ways of changing pieces? Maybe something like ProteanPieces.