uses crt, graph;
var
q:char;
beta,alfa,s,x,y,z:real;
a,b,a1,b1,a2,b2,a3,b3:integer;
d,m,i,j,k:integer;

procedure koordin(s,z,x,y:real; var a,b:integer);
begin
y:=y*0.8;
if x*x=0 then begin a:=0; b:=round(s*y/(s-z)*100); end else
begin
a:=round(s*sqrt(x*x+y*y)/(s-z)/sqrt(1+y*y/x/x)*100);
b:=round(s*sqrt(x*x+y*y)/(s-z)/sqrt(1+y*y/x/x)*100*y/x);
end;
if x*a<0 then a:=-a;
if y*b<0 then b:=-b;
a:=a+320;
b:=b+240;
if k=1 then a:=a-120 else a:=a+120;
end;

begin
initgraph(d,m,'');
alfa:=0;
setcolor(15);
repeat
cleardevice;
for k:=1 to 2 do begin
case k of
1:begin alfa:=alfa-0.1; end;
2:begin alfa:=alfa+0.1; end;
end;

for j:=1 to 2 do
for i:=1 to 5 do
begin
koordin(4,cos(alfa+i*pi/2),sin(alfa+i*pi/2),j*2-3,a,b);
if i=1 then moveto(a,b) else lineto(a,b);
end;

for i:=1 to 4 do
begin
koordin(4,cos(alfa+i*pi/2),sin(alfa+i*pi/2),1,a,b);
moveto(a,b);
koordin(4,cos(alfa+i*pi/2),sin(alfa+i*pi/2),-1,a,b);
lineto(a,b);
end;
end;

{alfa:=alfa+0.01;}      { atklaat sho un aizklaat 4 naakamaas rindas, }
{delay(100); }          { lai roteetu automatiski!                    }

q:=readkey;
while q=#0 do q:=readkey;
if q=#75 then alfa:=alfa+0.05;
if q=#77 then alfa:=alfa-0.05;

until (q=#27) or keypressed;
closegraph;
end.