code: function getVelocity(delta_time, delta_x, delta_y) {
      return {
        x: Math.abs(delta_x / delta_time) || 0,
        y: Math.abs(delta_y / delta_time) || 0
      };
    }
docs: calculate the velocity between two points
  @param   {Number}    delta_time
  @param   {Number}    delta_x
  @param   {Number}    delta_y
  @returns {Object}    velocity