To explain more clearly, Battery power circuit closed through magnets and the coils touching the magnets (i. e. Coil portion covering the train) and small current flows resulting creation of magnetic field. According to Lenz’s law the cause will be opposed. So opposite magnetic field will be created and Due to that magnetic repulsion and the train moves. The magnets are attached in reverse order among battery + and -ve, so the repulsion force will be added and train moves in same direction.

To avoid the short circuit induces of the coil portion under the train because of battery cover, the magnets are having more diameter and the train moving on the battery +ve side only.

This is my opinion only Naveen . Thanks for sharing such a beautiful videos.