On the Level (8)

Around Christmas each year the British spy agency puts out a puzzle intended to challenge the best solvers in the world. This is a puzzle you may or may not find difficult but regardless is pretty clever. It's part of a class of puzzles where the solver isn't provided any instructions. Figuring out the rules is part of the fun.

Solving this creative puzzle requires realization that there are 3 i/o points on the outside of each edge and 3 i/o points on the inside. This allows us to nest the images to create continuous circuits. Nesting 4 times allows for a complete circuit from start to finish (on the same level). Each time a boundary is crossed, write down the letter corresponding with the opposite of the moving direction.

TURNBYPI

Does this sound like the solution to the puzzle? No - sounds like directions. How cool! Rotating each nested level by pi (180 deg.) leads to the following diagram.

This time the circuit can be completed starting and ending on the outside (or zero) level! Tracing the circuit and tracking the letters:

F.......

The final solution is left for you to work out but the answer makes sense and matches the theme. We have the solution to the puzzle!

Feel free to contact me to check your answer or with questions.