function start(){
  update_reflections() ;
  Get('button_update').addEventListener('click', update_reflections) ;
}
function update_reflections(){
  var base_height = 600 ;
  var select = Get('select_units') ;
  var units = select.options[select.selectedIndex].value ;
  var np = parseFloat(Get('form_np').value) ;
  var GETs = '?' ;
  GETs = GETs + 'M='     + Get('form_M'   ).value ;
  GETs = GETs + '&m1='   + Get('form_m1'  ).value ;
  GETs = GETs + '&m2='   + Get('form_m2'  ).value ;
  GETs = GETs + '&m3='   + Get('form_m3'  ).value ;
  GETs = GETs + '&m4='   + Get('form_m4'  ).value ;
  GETs = GETs + '&pmin=' + Get('form_pmin').value ;
  GETs = GETs + '&pmax=' + Get('form_pmax').value ;
  GETs = GETs + '&np='   + Get('form_np'  ).value ;
  GETs = GETs + '&unit=' + units ;

  var height = 10 + base_height + 20*(np+2) ;
  Get('reflections_wrapper').style.height = height + 'px' ;
  var height = base_height + 20*(np+2) ;
  Get('reflections_wrapper').innerHTML = '<object type="image\/svg+xml" data="reflections.php' + GETs + '" name="reflections" width="600px" height="' + height + 'px"><\/object>' ;
  Get('link').href = 'index.php' + GETs ;
}
function Get(id){ return document.getElementById(id) ; }