...start with putting the topology generator to work
- turns out it is still challenging to write the ctrl-rules
- and one example tree looked odd in the visualisation
- which (on investigation) indicated unsound behaviour
...this is basically harmless, but involves an integer wrap-around
in a variable not used under this conditions (toReduce), but also
a rather accidental and no very logical round-up of the topology.
With this fix, the code branch here is no longer overloaded with two
distinct concerns, which I consider an improvement