code: func (c *Client) updateGravity() {
  	dist := c.origin.DistanceTo(c.coord).Seconds()
  	force := -1.0 * math.Pow(dist/c.config.GravityRho, 2.0)
  	c.coord = c.coord.ApplyForce(c.config, force, c.origin)
  }
docs: // updateGravity applies a small amount of gravity to pull coordinates towards
  // the center of the coordinate system to combat drift. This assumes that the
  // mutex is locked already.