How to play Fidchell

About Fidchell: Celtic Chess, from BoardGameGeek:

Played on a polar grid with variable numbers of positions on each circumference. One piece-type only (stones), each player starts with 27 stones, 8 placed at specific starting positions, 19 off board. Two game phases : placement and then movement. Play usually alternates between players. Custodian capture applies during each phase, successful capture allows a second move. The two players have asymmetric goals, however: white must build a continuous line of pieces from center to circumference, black must prevent this from happening.