open window 640,512
dim cs(180),sn(180)
for angle=0 to 180
 cs(angle)=cos(angle*pi/90)*400+320
 sn(angle)=sin(angle*pi/90)*400+256
next angle
label k
 t=t+1
 x=cos(t/90)*128+320
 y=sin(t/85)*128+256
 for a=0 to 179
 r=127+cos(m)*127
 b=127+cos(m*1.002)*127
 m=m+.175
 setrgb 1,255-r,b,r
 setrgb 2,r,0,b
 setrgb 3,r,0,b
 gtriangle x,y to cs(a),sn(a) to cs(a+1),sn(a+1)
next a
setdispbuf bu:bu=1-bu:setdrawbuf bu
goto k
