var metrics;

function calculateMetrics() {

  metrics = new BaselineRhythmMetrics();
  metrics.body_font_size_px = parseInt($('base_points').value);
  metrics.body_line_height_px = parseInt($('rhythm_points').value);
  $('css_output').update(metrics.toCSS());
  metrics.applyStyles();
}

window.onload = function() {

  $('base_points').onblur = function() { calculateMetrics(); }
  $('rhythm_points').onblur = function() { calculateMetrics(); }
}