code: function moveDrag(entity, world) {
    return function (dx, dy) {
      // This position updating is fairly naive - it lets objects tunnel through each other, but it suffices for these examples.
      entity.data.pos.x = this.ox + dx;
      entity.data.pos.y = this.oy + dy;
      world.simulate();
    };
  }
docs: Create a Raphael move drag handler for specified entity