I assume this is not a vaild shot. But what if it the opponent's, once in motion, hits an otherwise stationary disc of mine?
Also, if the opponent's disc is demoted, or even pushed of the board, as a result of an invalid shot, is it replaced, or does it stay where it ends up?
Assuming the opponent didn't hit any of your discs with any of their discs during the shot then their disc is removed along with any other of their own discs that were hit. Your disc would stay where ever it ended up or if it's touching the shooting line it gets removed from play.