The issue of check/mate is not as complex as it sounds. All it means is that on your turn, you are in check if your opponent could capture your king with his current number of moves. Since each piece can move only once per turn, this means that bishops', rooks', and queens' lines of attack merely need to be examined past any friendly pieces, provided the pieces in the way can be moved. In chess jargon, "discovered check" threats are actually checks.