In each center-piece, there are two magnets that repel each other. This act of magnets is called magnetic levitation, and this creates a spring-like feeling. It is only for the centers, and the corner-core magnets and the edge/corner magnets attract to each other like normal magnets do.
As for the edge/core magnets, they also repel, but since the corner/core magnets are there to snap back together, it will stay together. The core is still a corner-core magnet system, but as the edge magnets at the bottom of the tracks meet, they repel, and as the corner magnets come back into position, they snap back together.
At least, that is what I speculate.