Many markers with markers.js

<!DOCTYPE html>
<html>
  <head>
    <title>mmg: simple markers for Modest Maps</title>
    <style>
      #map {
        position:absolute;
        top:0;
        right:0;
        left:0;
        bottom:0;
      }
      body {
        font:13px/20px 'Helvetica';
      }
    </style>
    <link href='ext/controls.css' type='text/css' rel='stylesheet' />
  </head>
  <body>
    <div class='column'>
      <div id='map'></div>
    </div>
    <script type='text/javascript' src='src/mmg.js'></script>
    <script type='text/javascript' src='misc/chroma.min.js'></script>
    <script type='text/javascript' src='src/simplestyle_factory.js'></script>
    <script type='text/javascript' src='src/tooltip_wrap.js'></script>
    <script type='text/javascript' src='lib/modestmaps.min.js'></script>
    <script type='text/javascript' src='lib/wax.mm.min.js'></script>
    <script type='text/javascript' src='ext/movetip.js'></script>
    <script type='text/javascript'>
      wax.tilejson('https://a.tiles.mapbox.com/v3/tmcw.map-5vaivzxq.jsonp',
        function(tj) {
          var m = new MM.Map('map', [
              new wax.mm.connector(tj)
              ]);
          var step = 1;
          var ft = [];
          var colors = ['#fff', '#f00', '#ace', '#cae', '#fae', '#728'];
          for (var x = -70; x < -20; x += step) {
            for (var y = 30; y < 50; y += step) {
              ft.push({
                geometry: {
                  coordinates: [x, y]
                },
                properties: {
                  'marker-color': colors[y % colors.length],
                  'marker-size': 'small'
                }
              });
            }
          }

var l = mmg()
            .factory(simplestyle_factory)
            .features(ft);
          m.addLayer(l);
          m.extent(l.extent());
        });
    </script>
  </body>
</html>