def do_move(self, dt, buttons):
        """
        Updates velocity and returns Rects for start/finish positions
        """
        assert isinstance(dt, int) or isinstance(dt, float)
        assert isinstance(buttons, dict)

        newVel = self.velocity

        # Redirect existing vel to new direction.
        nv = newVel.magnitude()
        newVel = nv * self.impulse_dir

        mv = buttons['up']
        if mv != 0:
            self.stats['battery'] -= self.battery_use['linear']
            newVel += dt * mv * self.accel * self.impulse_dir
        else:
            brake = dt * self.deaccel
            if nv < brake:
                newVel *= 0
            else:
                newVel += brake * -self.impulse_dir

        nv = newVel.magnitude()
        if nv > self.top_speed:
            newVel *= self.top_speed / nv

        return newVel
Updates velocity and returns Rects for start/finish positions