@MarkReed The output of ⎕NQ and many other system functions is "shy", which means it will not display by default. If I ever start a new APL interpreter from scratch, I would definitely drop "shyness". Instead, display all results when running expressions interactively and require explicit output (⎕←) if you want a running function to display output.

Two confessions

1. I just found a solution for the next Quest, which I have to admit was partly by accident :\

2. I am still frequently suprised by the size or shape of the (intermediate) resutls. Which I fix sometimes by trial and error

Probably should try to construct the result in my head more often instead of immediatly testing it in the interpreter.