Centre disc

From Polarity

The red Centre Disc determines both the polarity of the game and who moves first. One side has a bar (north) and the other a spot (south). The orientation of the piece is determined by a toss at the start of the game.

Causing any disc to contact the centre disc is an immediate loss for the faulting player. You may not lean pieces against the centre disc. Some strategies suggest that choosing the same polarity as the centre disc gives a slight advantage due to pieces repelling as opposed to attracting the centre disc.