class Shape
{

}

class Rectangle : Shape
{
    public float width;
    public float height;
}

class Circle : Shape
{
    public float radius;
}

class ShapeTools
{
    public float Area(Shape shape)
    {
        if(Shape is Rectangle rect)return rect.width * rect.height;
        if(Shape is Circle circle)return circle * circle * Mathf.PI;
    }
}