I appreciate the positive feedback. Also, I am having the following extra ideas for
zoning types (in addition to industry catchment):
- City catchment (or 'building catchment')
- Unserved industries
- Unserved buildings
Edit: Well, as it turns out, doing 'industry/city catchment' won't be easy, since the catchment does not vary depending on industry, but rather depending on the type of station. The solution is thus to vary the colour of the tiles as they get further from the industries.
- 1-3 White (lorry/bus)
- 4 Blue (train station/some airports)
- 5 Green (docks/some airports)
- 6 Yellow (some airports)
- 7-9 Light blue (international airport)
And of course, there should be a 'station catchment', where you can see at a glance all tiles being served by your stations.
Edit 2: A little tease on the unserved buildings. It is however, not perfect. It would have produced the same results had I placed a lorry station, which cannot serve buildings. But checking for such will come!

- Notice which buildings are red, and which are not.
For the record, right now a building is a MP_HOUSE that accepts and/or produces mail and/or passengers.
Edit 3: And a showcase of station catchment!

- A combination of station catchment and unserved buildings. Notice how there are no unserved buildings!

- Testing whether the showcase is different from the actual handling.