open window 640,512
label k
 j=j+1
 c=cos(j/9.2)
 s=sin(j/9.4)
 cs=c*s
 i=127+cs*127
 r=(s+1)*i
 g=(c+1)*i
 b=(cs+1)*i
 setrgb 1,r,g,b
 setrgb 2,b,r,g
 setrgb 3,g,b,r
 gtriangle 640,512 to 640,0 to 0,0
 gtriangle 640,512 to 0,512 to 0,0
goto k
