Аполлониево Множество

uses CRT, GraphABC;
var 
    x, y, a, b: Real;
    r: Real;
    a0, b0: Real;
    a1, b1, a2, b2: Real;
    f1x, f1y: Real;
    x1, y1: Real;
 
begin
    setwindowcaption('Фракталы: Аполлониево Множество');
  setwindowsize(650, 500);
  clearwindow;
    x := 0.2;
    y := 0.3;
    a := 0;
    b := 0;
    Randomize;
    r := Sqrt(3);
    while not KeyPressed do 
    begin
        a := Random;
        a0 := 3*(1+r-x)/(sqr(1+r-x)+sqr(y))-(1+r)/(2+r);
        b0 := 3*y/(sqr(1+r-x)+sqr(y));
        if (a <= 1/3) and (a>=0) then 
        begin
            x1 := a0;
            y1 := b0;
        end;
        a1 := -1/2;
        b1 := r/2;
        a2 := -1/2;
        b2 := -r/2;
        f1x := a0/(sqr(a0)+sqr(b0));
        f1y := -b0/(sqr(a0)+sqr(b0));
        if (a <= 2/3) and (a > 1/3) then 
        begin
            x1 := f1x*a1-f1y*b1;
            y1 := f1x*b1+f1y*a1;
        end;
        if (a <= 3/3) and (a > 2/3) then 
        begin
            x1 := f1x*a2-f1y*b2;
            y1 := f1x*b2+f1y*a2;
        end;
        x := x1;
        y := y1;
        PutPixel(320+Round(x*50), 240+Round(y*50), clRed);
    end;
    ReadKey 
end.