WinFormでボールが壁で跳ね返るプログラム

mkdir プロジェクト名
cd プロジェクト名
dotnet new winforms
code .

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

namespace TickCountSample
{
    static class Program
    {
        /// <summary>
        ///  The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main()
        {
            Application.SetHighDpiMode(HighDpiMode.SystemAware);
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            
            var frm = new Form1();

            var picbox1 = new PictureBox { Dock = DockStyle.Fill };
            frm.Controls.Add(picbox1);

            var bgc = BufferedGraphicsManager.Current;
            var bg = bgc.Allocate(
                picbox1.CreateGraphics(), picbox1.DisplayRectangle);
            picbox1.Paint += (s, e) => bg.Render();


            frm.Show();

            var prev_tc = (double)Environment.TickCount64;
            var wait = 1000d / 60d;
            var next_tc = prev_tc + wait;

            int x = 50;
            int y = 50;
            int r = 16;

            int dx = 4;
            int dy = 4;
            int w = 800;
            int h = 450;

            while(frm.Created)
            {
                if ((double)Environment.TickCount64 > next_tc)
                {
                    x = x + dx;
                    y = y + dy;

                    if ((x + r) > w || x < 0)
                        dx = dx * -1;
                    
                    if ((y + r) > h || y < 0)
                        dy = dy * -1;

                    if ((double)Environment.TickCount64 < (next_tc + wait))
                    {
                        bg.Graphics.Clear(Color.Navy);
                        bg.Graphics.FillEllipse(Brushes.AliceBlue, x, y, r, r);
                        bg.Render();
                    }
                    next_tc += wait;
                }

                Application.DoEvents();
            }
        }
    }
}

dotnet build

dotnet run