I've found a pic of my "Brain Training" gizmo
You have to hit the heads as they light up or it makes a rather rude noise at you.
If you turn it upside down there's a little switch for advanced players. The heads light up in a semi-logarithmic sequence using your height in millimeters as a base number. I beat it regularly nowadays.
Unless it chooses an alpha-numeric sequence in which case I only beat it 51.2356% of the time.