TL;DR
Highlighting the reactors that are connected as neighbours during and after placement would increase legibility of what qualifies for the neighbour bonus.What?
Entities that would connect because of NeighbourConnectable should be highlighted when you select one. I imagine it would work the same way electric poles highlight what they power, roboports highlight what they connect to the network, etc.I made a quick example mod of what I desire (which I will make an icon for and publish in the meantime). It does not support the highlight during placement though.
Why?
Fusion reactors dodge the confusion by being being based on or directly matching the fluidbox connections, but it would help new users understand what the nuclear reactor means by "built next to other reactors".I do think it would also generally benefit modding, letting modders utilize the feature complexly without being incredibly confusing (and quickly test their definitions).
