Here, I will detail the use of inheritance.

Polygon.k

import Core;
export Samples.Polygon;

// The keyword 'base' allows inheritance.
// It automagically marks the destructor as 'virtual'.

base class Polygon
{
    int32 _edgeCount;

    public get int32 EdgeCount { return _edgeCount; }
    public abstract get double Area;

    public constructor(int32 edgeCount)
    {
        _edgeCount = Math.Max(3, edgeCount);
    }
}

class RightTriangle is Polygon
{
    double _width;
    double _height;

    public override get double Area { return _width * _height / 2.0; }

    public constructor(double width, double height) : base(3)
    {
        _width = Math.Max(width, 0.1);
        _height = Math.Max(height, 0.1);
    }
}

int32 Main(String[] arguments)
{
    Polygon* polygon = new RightTriangle(2.0, 3.0);
    Console.Write(polygon.Area).Write(NewLine);
    delete polygon;
    return 0;
}