pro show_slab
  !P.MULTI=[0,2,1]
  L=1

  for i=0,250 do begin
     snr=string(i,form='(i03)')
     name="snap_"+snr
     
     readnew,name,h,"HEAD"
     readnew,name,x,"POS"
     readnew,name,v,"VEL"
     readnew,name,id,"ID"

     jj=where(abs(x[2,*]-0.05) LT 0.01)
     jjb=where(abs(x[2,*]-0.05) LT 0.01 AND id[*] EQ 0)
     plot,x[0,jj],x[1,jj],psym=3,xr=[0,l],yr=[0,l],xst=1,yst=1,xtit='x',ytit='y',charthick=2,charsize=2
     oplot,x[0,jjb],x[1,jjb],psym=3,col=128

     plot,x[0,jj],v[1,jj],psym=3,xr=[0,l],yr=[-1.05,1.05],xst=1,yst=1,xtit='x',ytit='vy',charthick=2,charsize=2
     oplot,x[0,jjb],v[1,jjb],psym=4,col=128

     save_screen,"frame_"+snr
  end
  stop
end