Let me start by saying how much I love the general idea of the mod.

'Space Age' gave us four new planets with unique themes. Vulcanus with its endless source of metals and territorial worms, Fulgora with its upside-down approach to manufacturing, Gleba with its decaying bioengineered products and finally the frozen Aquilo (my least favourite, as keeping all the mashinery warm is definitely the least disruptive approach).

Honestly, I couldn't imagine anyone else coming up with anything as unique.
You did!
Castra's enemy-driven resource system is fundamentally different from any other planet's "economy".
I love the new approach!
I wonder what your plans are for the future of the mod. How do you want to develop the mod, what direction will it take?
Also a shout out to @hurricane. The machines look stunning and capture the Factorio art style perfectly!

Of course, I'm not the owner of the mod. I have no say in the direction you take it.
However, after all the initial praise (which is well deserved), the mod isn't exactly what I expected.

Let me explain:
What I was hoping for was some sort of "tower defence" game on Castra:
Endless streams of (initially easy to defeat) enemies that would drop "loot" when defeated. This loot would then be picked up by drones as the basis for production chains (or used immediately, e.g. ammunition drops). Basically, exactly what you are doing with those mashines (sorry, I forget what you called them), but much more dynamic.
Those mashines are actually a great starting point as they are, and surface-based resources are necessary as well, I guess. But a very large emphasis on these "spoils of war" would really make the Castra experience stand out.

Having constantly attacking combat drones from the start would also have prepared me for the appearance of those 'tanks of doom', which took me completely by surprise and forced me to restart my game with a fresh Castra landing. I hope I will be better prepared for what is to come. We'll see if the perimeter I've set up is enough to stop them.
As I said, I would have liked these tanks to drop especially valuable material, as they seem to be very powerful enemies. Defeating them should grant a nice "reward". (I suspect that balancing the combat capabilities of the enemies is a thing for later development stages of the mod. I am not sure, if the current relation of spawn-frequency and enemy power is sustainable. Constant upgrades through automatic research is an interesting idea. However, at some point it will become frustrating for the player. I am not sure if this line has already been crossed.)

The graphics:
As I am apparently spoiled by what the base game achieved with the planetary surfaces, I find the current planetary surface a bit lacking.
Creating new and unique tile sets is obviously only a secondary goal. Game mechanics first!
Are you planning to improve the surface visuals? (The light oil bodies of non-water don't blend well with the surroundings. There is no vegetation, which might be OK since the planet is devastated).
But what about scattered ruined machinery, shattered solar panels and toppled electricity pylons? These graphics already exist, and would help paint the picture of a battle-scarred planet (that is not decayed to the state of Fulgora).

Please don't take my criticism as an insult.
As I said, Planet Castra is a surprisingly unique mod and has the potential to be outstanding.
I will definitely follow your constant updates and just wish that factorio would support steam mods, which would make staying up to date so much easier.

Kind regards,
Hias_G

Thanks for the feedback! The original release of this mod was put together in basically 4 days since I (and a friend) wanted to do a modded planets run but there was a gap in machines missing that the Forge filled.
The rest kinda came up around that after experimenting with enemy force turrets and tech, and here we are.

So far, I've kinda heard 2 sides of balance where it's too difficult and it's too easy, so I've been hesitant to make any major balance changes yet.
I've considered going the route of having the enemies drop loot, but tbh loot is a half baked mechanic in the game. So much so that alien artifact loots got removed years ago. Technically, I could fake loot such that it's automatically marked for deconstruction like the data collector does, but I wasn't 100% on going down that route. I'll give it some more thought. Trying not destroy performance again lol.

As for starting with some early enemies to ease the transition to tanks, I could add something early game to help there. A combat robot is probably the best bet for this (Defender at green + military and then Destroyer after tanks at yellow). These would only appear once they get military science though so we'll see. It would definitely help add some missing variety to the enemy pool.

Gotta be careful though since I could see things start getting too annoying. If more enemies get added, I think there should definitely be some new tools. Maybe some kind of jammer to "capture" data collectors in range to prevent enemy spawns while its active.

And yeah, the map gen and graphics have been the lowest of priorities. Most of it is figuring out how the map generation works in 2.0 (so complicated imo), but I'll definitely see if I can add some more decorations around to spice things up.

Thanks again for all the feedback!

Well, I failed ... again.
Partly because I did not extend the security measures to my outposts (fast enough). It was planned, but I couldn't produce enough laser turrets in time.

But also because those tanks are able to cross the light oil seas.
Should they be able to, or is this a bug?
I assumed they would be blocked, as my mech-armoured alter-ego uses his flight mode to cross them.

Castra is maybe the best planet if you play with AAI vehicles! I am enjoying it so far, it's a run where I give them chance to do some science. Some other mods are a bit strange (tried gun turret shields, it overloaded their power supply). Both capture and reclaim mechanic would be very welcome :)

Castra enemies just completed planet discovery Castra, it made me wonder if they could also come and visit gleba or so. They could build a rocket silo (side objective) in order to raid other planets.

@Hias_G
Yeah laser turrets are heavily discouraged since the tanks have high resistance to them. Arguably even more due to steam power being relatively expensive due to water being more difficult to come by.

Tanks are fine to cross light oil oceans. It's treated the same as Fulgora's shallow portions of the ocean where you can walk over it without too much speed loss.

@raute
Enemy power is quite limited since you can technically steal power from it lol
So this was compensated for by making enemy specific turrets that take less power. So other mods like gun turret shields would need compatibility added. I'll look into that later.

Interstellar combat for enemies isn't being considered at the moment. Just because I feel it's enough to manage the planet itself (especially once the enemy researches artillery). Maybe in the future there could be a mod setting for this. I think that would also be a good way to handle biological warfare by dropping pentapods or biters once the enemy gets access to their eggs.

@Bartz24
now i pity them for the power theft :D

there are a few mods I am currently looking into (maybe forking) like the orbital bombardment (it's with ion cannons, but I'd love to assemble drop squads in space, maybe with pentapods - super good idea)
one fun thing with warriors is also loyalty and faith. I am not sure if the game engine likes my idea, but age of empires 2 had a pretty fun idea with the monk turning the faction of a (previously) hostile unit.

edit: forgot to mention that mod with protoss and zerg coming for you :)