Keys "s"=save "l"=load "b"=back once
Indigo and Azure are the Blue team. Maroon and Scarlet are the Red team.
In negotiating the barriers, knights are assumed to move first orthogonally. You may capture a unit from an allied army, but you do not check the allied king. You may not move into check. If a king is checkmated when his turn comes around, his whole army vanishes. If there is no legal move, skip the turn. For this reason, stalemate is unlikely, so all pawns promote to queens.
I couldn't figure out how to handle the en passant rule, so I skipped it. I may add the option to arrange the pieces in your fortress as you like at the onset.
I figured the pawns could capture around the corner of the fortress, but that bishops could not sneak out the rim of the door.
Thanks to Bishop Fish and Veronica Reid for help with the debugging.
Russian Fortress Chess
Bodlaender's Chess Variants
Hans Bodlaender's Chess Applet
Ed's Chess Variants
There are simple illustrations rather than strong opponents.
Bug reports? -- Thank you! Keep them coming!