I also made this game. It is called "Large Hnefatafl" and is 13x13 squares. Pieces are green and blue, of course...the king is designated by a different shape than the other defenders.
(hide) If you are waiting for your turn, click on "change" next to the "refresh" on the main page, then set refresh the page to 30 seconds to get your turn to move displayed faster. (Servant) (show all tips)