mixster

const
  largeRadius = 100;
  smallRadius = 50;
  largeLim = largeRadius * largeRadius;
  smallLim = smallRadius * smallRadius;
  imgSize = 400;
  cen = imgSize div 2;

var
  b, x, a, y, c: Integer;
  u: Boolean;
begin
  DisplayDebugImgWindow(imgSize, imgSize);
  b := BitmapFromString(imgSize, imgSize, '');

  a := 0;
  u := True;
  for c := 0 to largeLim do
  begin
    if (u) then
      Inc(a)
    else
      Dec(a);
    if (u) then
      x := Round(Sqrt(c) + Sqrt(a))
    else
      x := Round(Sqrt(c) - Sqrt(a));
    y := Round(Sqrt(largeLim - c) + Sqrt(smallLim - a));
    FastSetPixel(b, cen + x, cen - y, clRed);
    FastSetPixel(b, cen + x, cen + y, clRed);
    FastSetPixel(b, cen - x, cen + y, clRed);
    FastSetPixel(b, cen - x, cen - y, clRed);
    y := Round(Sqrt(largeLim - c) - Sqrt(smallLim - a));
    FastSetPixel(b, cen + x, cen - y, clRed);
    FastSetPixel(b, cen + x, cen + y, clRed);
    FastSetPixel(b, cen - x, cen + y, clRed);
    FastSetPixel(b, cen - x, cen - y, clRed);

    if (not InRange(a, 1, 2499)) then
      u := not u;
  end;

  DrawBitmapDebugImg(b);
end.