C# list of structures reference testing

struct-list-reference-test.cs

using System;
using System.Collections.Generic;

namespace struct_reference
{
    class Program
    {
        static void Main(string[] args)
        {
            Point p1 = new Point(10, 10);
            Point p2 = new Point(20, 20);
            Point p3 = new Point(30, 30);

            var list = new List<Point> { p1, p2, p3 }; // Members of list is not referencal equal to p1, p2, p3
            // list[0].X = 100; Compile err
            var ppap = list[0]; // ppap is new instance of point, just copied values of p1.
            ppap.X = 100;

            Console.WriteLine(p1); // => (10, 10), Not changed

            list[0].SetX(100);
            Console.WriteLine(p1);
            Console.Read(); // => (10, 10), Still not changed
        }
    }

    struct Point
    {
        public int X, Y;
        public Point(int x, int y)
        {
            X = x; Y = y;
        }

        public override string ToString() => $"({X}, {Y})";
        
        public void SetX(int new_x) => X = new_x;
    }
}