def update (self):
delta_velocity = Vector.null()<EOL>target_position = self.target.get_position()<EOL>sprite_position = self.sprite.get_position()<EOL>desired_direction = target_position - sprite_position<EOL>if <NUM_LIT:0.0> == self.los or desired_direction.magnitude <= self.los:<EOL><INDENT>desired_normal = desired_direction.normal<EOL>desired_velocity = desired_normal * self.sprite.get_max_velocity()<EOL>delta_velocity = desired_velocity - self.sprite.get_velocity()<EOL><DEDENT>self.last_delta_velocity = delta_velocity<EOL>return delta_velocity, self.power<EOL>
Calculate what the desired change in velocity is. 
        delta_velocity = acceleration * delta_time
        Time will be dealt with by the sprite.