procedure TMainForm.FormCreate(Sender: TObject);
begin
 Randomize;
 // nastavení náhodných čísel...
 MoveRect.Left:=Random(DXDraw1.SurfaceWidth-60);
 MoveRect.Top:=Random(DXDraw1.SurfaceHeight-40);
 MoveRect.Right:=MoveRect.Left+60;
 MoveRect.Bottom:=MoveRect.Top+40;

 StayRect.Left:=Random(DXDraw1.SurfaceWidth-120);
 StayRect.Top:=Random(DXDraw1.SurfaceHeight-80);
 StayRect.Right:=StayRect.Left+120;
 StayRect.Bottom:=StayRect.Top+80;

 Collision:=false;
end;

procedure TMainForm.DXTimer1Timer
(Sender: TObject; LagCount: Integer);
var gx,gy:integer;
begin
 // když nemůžeme kreslit tak pryč
 if not DXDraw1.CanDraw then exit;

 // draw grid
 for gx:= 0 to DXDraw1.SurfaceWidth div 50 do
  begin
   for gy:= 0 to DXDraw1.SurfaceHeight div 50 do
    begin
     DXImageList1.Items.Find('grid').Draw
     (DXDraw1.surface,gx*50,gy*50,0);
    end;
  end;

 // update klávewsnice
 DXInput1.Keyboard.Update;

 // má se hýbat s MoveRect ???
 if isLeft in DXInput1.Keyboard.States then // doleva
  begin
   Dec(MoveRect.Left);
   Dec(MoveRect.Right);
  end;
 if isRight in DXInput1.Keyboard.States then // doprava
  begin
   Inc(MoveRect.Left);
   Inc(MoveRect.Right);
  end;
 if isUp in DXInput1.Keyboard.States then // nahoru
  begin
   Dec(MoveRect.Top);
   Dec(MoveRect.Bottom);
  end;
 if isDown in DXInput1.Keyboard.States then // dolu
  begin
   Inc(MoveRect.Top);
   Inc(MoveRect.Bottom);
  end;

 // není náhodou kolize ???
 if InterSectRect(CollisionRect,MoveRect,StayRect)
 then
  Collision:=true
 else collision:=false;

 // kreslit RECt
 with DXDraw1.Surface.Canvas do
  begin
   Pen.Width:=2;
   Brush.Style:=bsClear;
   Pen.Color:=clYellow;
   Rectangle(MoveRect);
   Rectangle(StayRect);

   // kreslit collisionRect když je kolize
   if Collision then
    begin
     Pen.Color:=clLime;
     Font.Color:=clBlack;
     Font.Name:='Tahoma';
     Font.Style:=[fsBold];
     Font.Size:=15;
     TextOut(10,10,'!! KOLIZE !!');

     Brush.Style:=bsSolid;
     Brush.Color:=clRed;
     Rectangle(CollisionRect);
    end;

   // na to nezapomanout
   Release;
  end;

 // a flip ...
 DXDraw1.Flip;
end;

   MoveCircle, StayCircle:record
    CenterX,CenterY,Radius:integer;
    end;

   Collision:boolean;   // došlo ke kolizi ???
   R:real;              // pomocná proměnná

procedure TMainForm.FormCreate(Sender: TObject);
begin
 Randomize;
 // nastavení pozic kol a poloměrů..
 MoveCircle.Radius:=(Random(30)*2)+5;
 MoveCircle.CenterX:=Random
 (DXDraw1.SurfaceWidth-MoveCircle.Radius);
 MoveCircle.CenterY:=Random
 (DXDraw1.SurfaceHeight-MoveCircle.Radius);

 StayCircle.Radius:=(Random(40)*2)+5;
 StayCircle.CenterX:=Random
 (DXDraw1.SurfaceWidth-StayCircle.Radius);
 StayCircle.CenterY:=Random
 (DXDraw1.SurfaceHeight-StayCircle.Radius);

 Collision:=false;
end;

procedure TMainForm.DXTimer1Timer
(Sender: TObject; LagCount: Integer);
var gx,gy:integer;
begin
 // pokud nemůžeme kreslit, tak hned pryč
 if not DXDraw1.CanDraw then exit;

 // vymazat předchozí kresbu
 DXDraw1.Surface.Fill(0);

 // draw grid
 for gx:= 0 to DXDraw1.SurfaceWidth div 50 do
  begin
   for gy:= 0 to DXDraw1.SurfaceHeight div 50 do
    begin
     DXImageList1.Items.Find('grid').Draw
(DXDraw1.surface,gx*50,gy*50,0);
    end;
  end;

 // update klávesnice
 DXInput1.Keyboard.Update;

 // pohnout s MoveCircle ???
 if isLeft in DXInput1.Keyboard.States  // doleva
  then Dec(MoveCircle.CenterX);
 if isRight in DXInput1.Keyboard.States // doprava
  then Inc(MoveCircle.CenterX);
 if isUp in DXInput1.Keyboard.States    // nahoru
  then Dec(MoveCircle.CenterY);
 if isDown in DXInput1.Keyboard.States  // dolu
  then Inc(MoveCircle.CenterY);

 // nedošlo mezi kruhy ke kolizi ???
 R:=Sqr(MoveCircle.CenterX-StayCircle.CenterX)+
    Sqr(MoveCircle.CenterY-StayCircle.CenterY);
 R:=Sqrt(R);
 if R <= (MoveCircle.Radius+StayCircle.Radius)
  then Collision:=true
 else Collision:=false;

 // kreslit kruhy
 with  DXDraw1.Surface.Canvas do
  begin
   Brush.Style:=bsClear;
   Pen.Width:=2;
   if Collision then
    begin
     Pen.Color:=clLime;
     Font.Color:=clBlack;
     Font.Name:='Tahoma';
     Font.Style:=[fsBold];
     Font.Size:=15;
     TextOut(10,10,'!! KOLIZE !!');
    end
   else
    begin
     Pen.Color:=clYellow;
    end;

   Ellipse(MoveCircle.CenterX-MoveCircle.Radius,
   MoveCircle.CenterY-MoveCircle.Radius,
   MoveCircle.CenterX+MoveCircle.Radius,
   MoveCircle.CenterY+MoveCircle.Radius);

   Ellipse(StayCircle.CenterX-StayCircle.Radius,
   StayCircle.CenterY-StayCircle.Radius,
   StayCircle.CenterX+StayCircle.Radius,
   StayCircle.CenterY+StayCircle.Radius);

   // na tohle nezapomenout !!!!
   Release;
  end;

 // a flip...
 DXDraw1.Flip;
end;