Helpcompelmate = "help-selfmate". It is like a selfmate where black and white cooperates until the last move to reach a position where white can force black to mate in one move. White starts as in ordinary selfmates.
Nightrider (N) = a piece that moves on "knight-lines", i.e., it kan make
1, 2 or 3 successive knihgt moves in the same direktion.
(From hereon I reserv 'N' for nightriders and will use 'S' to denote knights)
Rose (Ro) = a piece that moves in "knight-circles". A rose on c3 on an empty board can for example reach c3-b5-c7-e8-g7-h5-g3-e2 in one move. To return to its start square (c3) is not considered to be a move.