Keys "s"=save "l"=load "b"=back once
Christiaan Freeling's game. Kings may not leave their castles. Check & checkmate as usual, but actual captures except by the king only occur between a defender in the castle and an attacker on the castle wall. Rooks stopping in enemy castle become queens.
Chad and other games -- inventor's site
These are simple illustrations rather than strong opponents.
Bug reports? -- Thank you! Keep them coming!