program circ_ani
      integer pgopen
      if( pgopen('/xwin') <= 0 ) stop
      xmin = 0.0
      xmax = 4.0
      ymin = 0.0
      ymax = 4.0
      call pgenv(xmin,xmax,ymin,ymax,1,0)
      x=2.0
      y=2.0
      d_theta = 2*3.14159/36000
      theta = 0.0
      xold=x
      yold=y
      rold=1.0
      call pgsfs(2)
      do i=1,100000
        theta = theta + d_theta
        r= 1.0 + 0.3*sin(theta)
        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
      end do
      call pgclos
      end