program anim

      implicit none
      real x,y,r,theta,d_theta,rold
      integer idummy,pgopen,i

      idummy=pgopen('/xwin')
      call pgenv(-5.0,5.0,-5.0,5.0,1,0)

      call pgsfs(2)
      x=0
      y=0
      r=2
      rold=r

      call pgcirc(x,y,r)

      d_theta=2*3.1416/3600
      theta=0
      do i=1,100000
        theta = theta + d_theta
        r=2+sin(theta)
        call pgbbuf
        call pgsci(0)
        call pgcirc(x,y,rold)
        call pgsci(1)
        call pgcirc(x,y,r)
        call pgebuf
        rold=r
      end do

      call pgclos
      end