Good catch for the cached entities.  Alright I think I've finished this up so we might have it now. Cool enough by replacing the method to retrieve snappable entites, a couple vanilla bugs for fixed just like that; notably the inability to continue wall placement in fog of war, but also inability to build from captured walls. I've listed all features achieved in opening comment. I've tested everything I could thing of to see if any exceptions are left unhandled but I think everything seems so much better now then it ever was. 

Hi everyone, I'm "El Maker" (it's not my real name) and  I love playing 0 A.D. !!  I've been playing 0 A.D. for a few years now (I’m not very good at it, but I really enjoy it!). After discovering this amazing project, I’ve developed a genuine interest in helping its development and contributing in any way I can. I’ve already explored the forum and found several topics that inspired me — there are a few areas where I think I could help or bring new ideas. I’m highly motivated and would love some guidance on how to get started ! My ideas (or areas where I’d like to help): –First of all : the civilisations such as Etruscans, Numidians, Nabateans or Dacians (I've seen that there are a lot's of civilisations that you want to add so I can help !) – Secondly : improve the Gaïa system (not fauna or flora but the "humans" : pirates, itinerants bandits ...) --> I've seen that in the Big Eyecandy section (but anyperson anwsered me) – Thirdly : (it's not THE ONE but I would be cool in my opinion) change the starts of every civilisations (in order to have different beginnings of games and strategies that really change depending on the civilizations) Any advice or feedback would be greatly appreciated. I’d love to collaborate in this amazing project !! Thanks in advance for your time !! El Maker  

You could either define it in the GUI globally somewhere and then pass it to every GuiInterface call, or just make it a member of the GuiInterface directly. The Engine.PickSimilarPlayerEntities method does not exist in the simulation scripting context, but the same thing can be achieved through the GetEntitiesByPlayer method combined some additional manual checks. That would also allow filtering entities by the "Tower" class instead of their template names (as you mentioned in the comment), if wanted. By the way, the GUI already caches entity states (in g_EntityStates).

When I tried to do so, it gave me errors, telling me rustc is too old. I read later in that thread that I need to install rustup, but there was no instructions for it. Ideas?