program reflective_walls_skip_d_inner
      real*8 x,y
      real x_inner(5),y_inner(5)

      write(*,*)'Vx?'
      read(*,*)vx
      write(*,*)'Vy?'
      read(*,*)vy

      i_dummy=pgopen('/xwin')
      xmin=-10
      xmax=10
      ymin=-10
      ymax=10
      r=0.3
      wdth=(1+0.1)*r
      call pgenv(xmin-wdth,xmax+wdth,ymin-wdth,ymax+wdth,1,-1)
      call pgsfs(2)

      x_inner_min=-1.2;x_inner_max= 1.2
      y_inner_min=-5.0;y_inner_max= 5.0

      x_inner(1)=-1.2+wdth;y_inner(1)= 5.0-wdth
      x_inner(2)= 1.2-wdth;y_inner(2)= 5.0-wdth
      x_inner(3)= 1.2-wdth;y_inner(3)=-5.0+wdth
      x_inner(4)=-1.2+wdth;y_inner(4)=-5.0+wdth
      x_inner(5)=-1.2+wdth;y_inner(5)= 5.0-wdth
      call pgline(5,x_inner,y_inner)

      x=-9
      y=-9
      xold=x
      yold=y
      dt=0.0000001

      n_draw = 100

      do i=1,1000000000

        if(x>xmax) vx=(-1)*vx
        if(x<xmin) vx=(-1)*vx
        if(y>ymax) vy=(-1)*vy
        if(y<ymin) vy=(-1)*vy

        if( (y>y_inner_min) .and. (y<y_inner_max) ) then
          if( (x>x_inner_min) .and. (x<x_inner_min+0.1) ) vx=(-1)*vx
          if( (x<x_inner_max) .and. (x>x_inner_man-0.1) ) vx=(-1)*vx
        end if

        if( (x>x_inner_min) .and. (x<x_inner_max) ) then
          if( (y>y_inner_min) .and. (y<y_inner_min+0.1) ) vy=(-1)*vy
          if( (y<y_inner_max) .and. (y>y_inner_max-0.1) ) vy=(-1)*vy
        end if

        x=x+vx*dt
        y=y+vy*dt

        if(mod(i,n_draw)==0)then
          call pgbbuf
          call pgsci(0)
          call pgcirc(xold,yold,r)
          call pgsci(1)
          call pgcirc(real(x),real(y),r)
          call pgebuf
          xold=real(x)
          yold=real(y)
c         write(*,*)'x,y,Vx,Vy =',x,y,vx,vy
c         write(*,*)'x =',x
        end if

      end do
      call pgclos
      end