private static bool isUsefulMove(Coin[,] state, Cell source, Cell dest)
{
Offset delta = dest.Minus(source);
var right = delta.RotateCW();
var left = delta.RotateCCW();
var color = state.get(source);
if(color == Coin.None)
return false;
if (state.getSafe(dest.Plus(delta)) == color && state.getSafe(dest.Plus(delta).Plus(delta)) == color)
return true;
if (state.getSafe(dest.Plus(right)) == color && state.getSafe(dest.Plus(right).Plus(right)) == color)
return true;
if (state.getSafe(dest.Plus(left)) == color && state.getSafe(dest.Plus(left).Plus(left)) == color)
return true;
if (state.getSafe(dest.Plus(left)) == color && state.getSafe(dest.Plus(right)) == color)
return true;
return false;
}