Inherited global variable cannot be accessed

I am writing a small program that is supposed to create differently shaped rooms from a base of a square. The shapes are supposed to inherit from the square, which contains List of their vertices.

Room (Parent class) code:

class Room
{
    private List<Point> vertices;
    private int oX;
    private int oY;
    private int width;
    private int height;

    public Room(int oX, int oY, int width, int height)
    {
        vertices = new List<Point>();
        addVertice(new Point(oX, oY));
        addVertice(new Point(oX + width, oY));
        addVertice(new Point(oX, oY + height));
        addVertice(new Point(oX + width, oY + height));

        this.width = width;
        this.height = height;
   }
}

Then I inherit LShape from Room, but the Visual Studio says that the vertices variable cannot be accessed due to its protection level.

Code for LShape (child) class

class LShape: Room
{
    public LShape(int oX, int oY, int width, int height, List<Point> verticesList)
    {
        vertices = verticesList;
    }
}

According to all the tutorials I found, this should be working, even if the parent's members are private.

Can someone explain to me where my error is, or where am I misunderstanding the concepts? Also If you have any good tutorials on inheritance, I'd be thankful.

Thank you.