(17.12.2014) Here is one join problem with Circle SneK. It was born during the conversation between me and Pierre about the 2^nd KoBulChess TT - Christmas Tourney 2014. There are still 4 days for all of you to participate on it! 

Circle SneK:

When a Queen is captured - a Rook (or Royal Rook) of the same color (if exists on the board) becoming Queen;

When a Rook is captured – a Bishop (or Royal Bishop) of the same color (if exists on the board) becoming Rook;

When a Bishop is captured - a Knight (or Royal Knight) of the same color (if exists on the board) becoming Bishop;

When a Knight is captured – a Queen (or Royal Queen) of the same color (if exist on the board) becoming Knight.

Only one piece may change its type after a capture. In case of option – the capturing side choose which piece will be transformed.

The capture and the change of type is a single move. If this full move result a selfcheck - the capture is forbidden. 

The capture of a pawn is normal. The capture is normal also in the case when there is no piece on the board which should be transformed. Castling with Royal piece is not allowed.