-Generator variant, called "Matrix" ?
-Peces on first rank never move but generate new pieces. Pawn don't generate.
-A generator captured and replaced by a similar piece does not generate.
-King does not generate. No castling. En passant possible?
-Goal is still checkmate.
+Merge variants 1, 2 (3) into one with sub-variant selection when starting a game (New Game + vs engine + analyse)
+E.g. Checkered 1 & 2 into one, and so on.
+Need additional field in variant code... in a generic way (radiobutton or select or checkbox?)