program review_anim
      i_dummy=pgopen('/xwin')
      xmin=-4
      xmax=4
      ymin=-4
      ymax=4
      call pgenv(xmin,xmax,ymin,ymax,1,0)

      dr=2*3.14/3600
      do i=1,100000
        x=0.0
        y=0.0
        r=3.0+sin(i*dr)
        call pgbbuf
        call pgsci(0)
        call pgcirc(xold,yold,rold)
        call pgsci(1)
        call pgcirc(x,y,r)
        call pgebuf
        xold=x
        yold=y
        rold=r
      enddo
      end