Greg,

There are two rows of tiles, one for the left foot and one for the right foot. As you give the first left step, stepping for example on the left white tile, it moves towards you and disappears from your sight bringing next to you the white tile on the right side for you to give another step.

Gait Aid also helps you with the problem of drop foot. because if you step with a flat foot instead of the heel first, the tiles do not move. It really gives you feed back as how you are walking.
Margarita