In Seirawan Chess are used another names and letters for Archbishop and Chancellor. There is Hawk and Elephant (H and E). In material_conditions.dart on line 75 should be:
soloMaters: ['P', 'Q', 'R', 'A', 'C', 'E', 'H'],
or change the definition of Seirawan chess with customized materialConditions.
In Seirawan Chess are used another names and letters for Archbishop and Chancellor. There is Hawk and Elephant (H and E). In material_conditions.dart on line 75 should be:
soloMaters: ['P', 'Q', 'R', 'A', 'C', 'E', 'H'],
or change the definition of Seirawan chess with customized materialConditions.