Не работает движение по кругу в делфи 10.4

unit Unit18;
 
interface
 
uses
  Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
  Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.Buttons, Vcl.ComCtrls,
  Vcl.ExtCtrls;
 
type
  TForm1 = class(TForm)
    Shape1: TShape;
    Shape2: TShape;
    Shape3: TShape;
    Shape4: TShape;
    Shape5: TShape;
    Shape6: TShape;
    Shape7: TShape;
    Panel1: TPanel;
    GroupBox1: TGroupBox;
    Label1: TLabel;
    Edit1: TEdit;
    UpDown1: TUpDown;
    Label2: TLabel;
    Edit2: TEdit;
    UpDown2: TUpDown;
    Label3: TLabel;
    Edit3: TEdit;
    UpDown3: TUpDown;
    GroupBox2: TGroupBox;
    Label4: TLabel;
    Label5: TLabel;
    Label6: TLabel;
    Edit4: TEdit;
    UpDown4: TUpDown;
    Edit5: TEdit;
    UpDown5: TUpDown;
    Edit6: TEdit;
    UpDown6: TUpDown;
    BitBtn1: TBitBtn;
    procedure First;
    procedure BitBtn1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.dfm}
 
var
k: integer;
i: integer;
t1,t2,t3: integer;
n1,n2,n3: integer;
 
 
 
procedure TForm1.First;
begin
  t1:=StrToInt(Edit1.Text);
  t2:=StrToInt(Edit2.Text);
  t3:=StrToInt(Edit3.Text);
  n1:=StrToInt(Edit4.Text);
  n2:=StrToInt(Edit5.Text);
  n3:=StrToInt(Edit6.Text);
end;
 
procedure TForm1.BitBtn1Click(Sender: TObject);
begin
  inc(k);
  First;
  if k mod 2=0
   then BitBtn1.Caption:='Пуск'
   else BitBtn1.Caption:='Стоп';
  while k mod 2=1 do
  begin
    inc(i);
    Shape5.Left:=n1*round(100*sin((pi*i)/(t1*50)))+275;
    Shape5.Top:=-round(100*cos((pi*i)/(t1*50)))+275;
    Shape6.Left:=n2*round(175*sin(pi*i/(t2*50)))+275;
    Shape6.Top:=-round(175*cos(pi*i/(t2*50)))+275;
    Shape7.Left:=n3*round(250*sin(pi*i/(t3*50)))+275;
    Shape7.Top:=-round(250*cos(pi*i/(t3*50)))+275;
    Sleep(50);
    Application.ProcessMessages;
  end;
 
end;
end.

 Application.MainFormOnTaskbar := True;