ectorAll('.light--' + active);
          for (var i = 0; i < els.length; i++) {
            els[i].setAttribute('visible', true);
          }
        }

        var num = 18;
        var gap = 3;
        for (var x = -num; x < num; x += gap) {
          for (var z = -num; z < num; z += gap) {
            addTower({position: {x: x, y: 0, z: z}}, 9);
          }
        }

        function createCube (opts) {
          opts = opts || {};
          var cube = document.createElement('a-entity');

          opts