{$reference 'System.Windows.Forms.dll'}
{$reference 'System.Drawing.dll'}

uses System, System.Windows.Forms;
var
 f : Form;
 btn : Button;
procedure ButtonClick(sender: object; e: EventArgs);

begin
 MessageBox.Show('Hello world!');
end;
begin
 f := new Form;
 var w := f.Width;
 var h := f.Height;
 btn := new Button;
 btn.Left := integer((f.Width - btn.Width)/2);
 btn.Top := integer((f.Height - btn.Height)/2)-10;
 btn.Text := 'Click me';
 btn.Click += ButtonClick;
 f.Controls.Add(btn);
 Application.Run(f);
end.