open window 640,512
setrgb 1,0,0,80
setrgb 2,0,80,30
setrgb 3,255,255,255
label k
 j=j+1
 c=cos(j/9.1)*sin(j/9.2)
 v=sin(j/9.3)
 x=320+c*320
 y=256+v*256
 gtriangle 0,0 to 640,0 to x,y
 gtriangle 0,0 to 0,512 to x,y
 gtriangle 640,512 to 640,0 to x,y
 gtriangle 640,512 to 0,512 to x,y
goto k
