Rim Sparse Extreme Impossible in 806 turns

[Gilmoy]

I dove into this little gem a few weeks ago, and quickly increased challenge to Impossible.
I learned to fear xeno AIs' exponential colonization creep, and how to beat them.
I finally played out the string to finish off an Extreme Impossible win, my 1st-ever win.

The Rim: 100x100 (93 worlds) Sparse Extreme Impossible
Date 16.26 (Turn 806)
Factions (Thulun, Javat, Steel Song)

Xeno AIs were oddly timid on this map, and soon ceased expanding.
You start on the east 1/4, and in fact you own the entire east 1/4 strip from top to bottom.
The 3 xeno AIs are NW, W, and SW. They soon border each other, and cease expanding.
In the order that I killed them:

093,103 XP = L29 Jyeeta Xeno, ~12 worlds
177,186 XP = L35 Nyktos Xeno, ~14 worlds
397,078 XP = L46 Sidtax Xeno, ~29 worlds

Half the fun for me was to see planet names and ship weapons I recognize from ST:F
Some unremarkable weapons in ST:F are a Big Deal here because of their research cost.

My Sparse worlds had Quality 6 - 15, none larger than a Prime world.
I researched up to Hab 5 and Terraforming 1, plus Javat's Orbital Refinery 3.
No planet ever lost Morale from overcrowding.
I think this means 3 AIs is a lightweight threat, so you win before the overcrowding phase.

I played most of the game with fighters + carriers, and surprisingly few of each.
+ 2 assault fighters
+ 6 light gun fighters (2 AP engine + 1 AP light gun)
+ 2 repair carriers
+ 2 refuel carriers

That sufficed to make 2 half-fleets, 1 to invade and 1 to rush home and stop a World Killer.
Sidtax AI sent only ~8 World Killers total, which cost me a few points of Quality and pop.
The other two AIs mounted nearly zero threat all game, and waited to die.

I kept all 3 of my starting ships alive
31 XP Explorer
33 XP Templar Defender
40 XP Templar Defender

I learn that high-end Invasion modules are massive
I skipped Coordinated Operations 1-3 (Angelic/Sephora Drop Ship).
I went directly to Starship Construction 11 and Deep Space Tactics 1-3 for:

2,180 mass Skyfire Drop Ship
2,460 mass Archangel Drop Shuttle + Planetary Invasion 3

I squeezed Archangel into 5100 mass, but skimped Level to 3 and Armor to 5. Ugh.
Those invasion transports sucked: they regularly ate 50-70 damage instead of 30-50.

One of ST4X's brilliant little nuggets is that Reactors techs are also your hull size techs.
I beelined to Starship Construction 14 and Superscale Reactors 1-2 for 6000 mass.
Then I made Archangels at Level 5 with 12 Armor, and they took 0(!) damage, but probably because Sidtax was down to its last 1 planet and I had it fully surrounded.

I essentially ignored all weapon techs and fighting ship designs.
The early fighters sufficed, all game long.
AI ship Rating maxed out at 6, probably because I killed them dead to stop their XP gain.
Without high-tech Crew +Attack bonuses, my fighters do miss 1/2 or more of their shots, but that sufficed to achieve an infinity:0 kill ratio.

I always Invade to purge xeno worlds, then colonize those with 11+ Quality.
I colonized 4 of 12 from Jyeeta, then 4 of 14 from Nyktos, then 10 from Sidtax.
I never Bombard to 0 Quality, so I'm still missing that Steam badge.
Xeno worlds are my worlds in the end, I don't bombard my own worlds.

Impossible difficulty seems to be correlated with a greater frequency of bad diplomatic relations, e.g. Trade Alliance changes into Spy Battle. This can drive your income negative, which could bankrupt you temporarily and disable all new Builds. In this game, these were always transient events, quickly (or very, very slowly ) resolved using the right diplomatic tool, and then a patient rebound to positive credits. I envision my empire's economy in a long game to trace out a sine-like curve, with perhaps 5-10 distinct transient phases of being underwater. This, too, shall pass.

~~~~~~~~

I previously tried the Degla Abundant 6 Xeno Extreme map, and got buried.

Now I see ST4X as a frantic race to project strength and proactively invade AIs to stop their Colony Ship spam. Hence the grand strategic flaw I made on a 6-xeno map was to sit in the center and wait for them, which cannot scale up.

+ I wonder if it's feasible to fighter-swarm AI space and deny Colony Ships.
Suppose we commit 4 fighters + 1 carrier, and sit within an AI's space while it's at ~8 worlds. Can this stop its further expansion?

The alternative is that you do nothing and the AI leisurely strolls to 30 worlds, then buries you in 20-ship wave attacks. And that's from one AI; there are 5 others. You surely can't wait in the center and defend all 6 directions.

I may try that next :p