private void play_Click(object sender, EventArgs e)
          {

               string path_name = Application.StartupPath;
                
               Process game = new Process();
               game.StartInfo.FileName = "The Real Life ALPHA 0.5.exe";
               game.StartInfo.WorkingDirectory = Path.Combine(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location), path_name);
               game.Start();

          }

Path.Combine(Application.StartupPath, "файл_игры.exe")

int main()
{
  cout << "С днём программиста!" << endl;
}