getCurrentCenterOfMass() {
    let total = new Vector2(0, 0);
    let count = 0;

    for (var i = 0; i < this.graph.vertices.length; i++) {
      let vertex = this.graph.vertices[i];

      if (vertex.positioned) {
        total.add(vertex.position);
        count++;
      }
    }

    return total.divide(count);
  }
Returns the current (positioned vertices so far) center of mass.

@returns {Vector2} The current center of mass.