its a illustrated koch snowflake

snowflake.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace snowflake_
{
public partial class Form1 : Form
{
    public Form1()
{

InitializeComponent();
this.Paint += new PaintEventHandler(Form1_Paint);
}
 
private void Form1_Paint(object sender, PaintEventArgs e)
        {
            DrawKochSnow(e.Graphics);
        }


        private void figure (Point p1, Point p2, Graphics g) // Polyline composed of 4 basic line segments
        {
            Point p3 = new Point(p1.X + (p2.X-p1.X) / 3, p1.Y + (p2.Y-p1.Y) / 3); // coordinates of the third point
            Point p4 = new Point(p1.X + (p2.X-p1.X) * 2 / 3, p1.Y + (p2.Y-p1.Y) * 2 / 3); // coordinates of the third point
            Point p4XD3 = new Point(p4.X-p3.X, p4.Y-p3.Y); // the coordinates of p4 relative to p3
            //int x = (int)(p4XD3.X * Math.Cos(Math.PI / 3)-p4XD3.Y * Math.Sin(Math.PI / 3));
            //int y = (int)(p4XD3.X * Math.Sin(Math.PI / 3) + p4XD3.Y * Math.Cos(Math.PI / 3));
            // Note that the vertical coordinate of the computer screen is opposite to the mathematical one, so mathematically rotating counterclockwise is equivalent to clockwise rotating on the computer
            int x = (int)Math.Round(p4XD3.X * Math.Cos(Math.PI / 3) + p4XD3.Y * Math.Sin(Math.PI / 3));
            int y = (int)Math.Round(p4XD3.Y * Math.Cos(Math.PI / 3)-p4XD3.X * Math.Sin(Math.PI / 3));
            Point p5XD3 = new Point(x, y); // The coordinates of the raised point p5 relative to the point p3
            Point p5 = new Point(p3.X + x, p3.Y + y); // the coordinates of p5 relative to the origin
            Pen pen = new Pen(Brushes.Black, 1);
            double length = Math.Sqrt(Math.Pow(p2.X-p1.X, 2) + Math.Pow(p2.Y-p1.Y, 2)) / 3;
            //Console.WriteLine(length);
            if (length> 20) // The iteration can be controlled by the length of the final line segment
            {
                figure(p1, p3, g);
                figure(p3, p5, g);
                figure(p5, p4, g);
                figure(p4, p2, g);
            }
            else
            {
                g.DrawLine(pen, p1, p3);
                g.DrawLine(pen, p3, p5);
                g.DrawLine(pen, p5, p4);
                g.DrawLine(pen, p4, p2);
            }
        }


        private void DrawKochSnow(Graphics g) // Koch snowflake (the Swedish Koch proposed the famous "snowflake" curve in 1904)
        {
            int length = 480;
            Point origin = new Point(this.ClientSize.Width / 2, this.ClientSize.Height / 2);
            g.FillEllipse(Brushes.Blue, new RectangleF(origin, new Size(10, 10)));
            // Calculate the vertices of the triangle so that its center coincides with the center of the window
            Point A = new Point(origin.X-length / 2, (int)(origin.Y + length / (2 * Math.Sqrt(3))));
            Point B = new Point(origin.X, (int)(origin.Y-length / Math.Sqrt(3)));
            Point C = new Point(origin.X + length / 2, (int)(origin.Y + length / (2 * Math.Sqrt(3))));
            figure(A, B, g);
            figure(B, C, g);
            figure(C, A, g);
        }
        

    }
}