The levels start off very simply. Actually, way too easy.
Very gradually, new mechanics are added. White spokes can move, but they don't get eliminated. Black spokes can't move or get eliminated.
Other elements: spokes normally stay on their hexagons, unless they pass through a portal. Also, when a spoke hits a certain node, other hexagons will shift across the board, quite unexpectedly. Similarly, invisible hexagons suddenly appear.
I don't know how many levels there are. But I got up to 8-4. There might even be other game elements that I haven't gotten too yet. Other games are beckoning.