Pure Round Trip
A unit undergoes a sequence of moves, not necessarily consecutive, that returns the unit back to a square earlier visited. The length of the cycle is the number of moves taken to return to an earlier square, with no squares revisited *during* the circuit, and should be at least 3 (else it's just A to B and back to A, and prefer SWITCHBACK).
Circuit length is 5, starting from first visit to c3.
The piece(s) that perform(s) a cycle are shown (in German letter symbols KDTLSBkdtlsb: upper case = white, lower case = black).
Pure round trips in different phases are separated by "comma".
For example: Pure Round Trip(K,k)
Compare with ROUND TRIP and SWITCHBACK