https://brainking.com/en/GameRules?tp=47&fwa=ArchivedGame!g=8204276$i=1
+https://musketeerchess.net/games/cerebral/rules/rules.php
+http://history.chess.free.fr/rollerball.htm
+
Squatter Chess: safe on last rank = win
Companion Chess : pieces of same nature don't attack each others
https://www.chessvariants.com/difftaking.dir/brotherhood.html