I just finished a game, well, was forced to finish it
This was a 50 planets, two 7.6 difficulty AIs: One-Way Doormaster and Sledgehammer.
My home planet was the one in the middle (a bit above the scanline in the screenie), had Space Tank as a starting bonus ship. I slowly explored and expanded to the boundaries of level 3 and level 4 worlds which posed a serious problem in the beginning of the game. I couldn't get my scouts past those and having Black Hole Machine on almost every AI world I couldn't just use transport ships to move scouts past those worlds. So I just let them be, fortifying the wormholes and conducting suicidal Warp Gates strikes where necessary.
Finding Dyson Sphere in cut off part in top left was a big help - it allowed me to easily capture all surrounding worlds and kept the level 3 planet on top a safe choke point that I didn't even need to capture for the time being. I just sent a bunch of cleanup drones with light escort-distraction to clear out some of the defenses built up in there and mauled by dyson spawns.
As the game progressed, I captured two advanced labs, one gave me Eyebots, one Electric Shuttles, also captured Core Acid Sprayers fabricator. Then I began expanding south, capturing one level 3 world in the process - nothing interesting on it, just that it blocked my route and was too close to my home world. Then I found a Broken Black Widow Golem (the spike of the south triangle) which I managed to capture and then used to help capture worlds between it and my home world to close the gaps and move my forces further south. Capturing next two worlds (south corner of the triangle and the planet beyond it) was easy. First one had zenith power generator and ion cannon that I chose to capture and the last planet had Broken Hive Golem on it. Oh goodie, I thought. I even opened the Zenith storage-cache thingy that let me buff up my strike force nicely.
But then things went, well, south. Pear shaped.
There were revenge guard posts on three worlds - two I was prepared for: one attack happened on the world next Dyson Sphere, sadly the Acid Sprayer fabricator was lost, the other attack hit my home world but I managed to hold it off long enough for my quick reaction force to reach the site and kill the attackers.
The problems started when I missed the third revenge guard post. I went on to quickly destroy the command center on that planet to prevent reinforcements and turrets rebuilding and then my home world got revenge attacked again. When I went to investigate and send reinforcements I noticed that there is a Raid Starship wrecking havoc on the infrastructure there, that somehow got there unnoticed by me. That wasn't so bad on its own. What was bad was that I just defended against a 1600 strong CPA so it took time for the reinforcements to get to my home world. And then some other larger attacks came from the level 3 planet in the middle and level 4 planet - they were between 60 and 80 ships strong but they tore through my tier 1 defenses and caused chaos. So I had to spread out my forces some to kill them all. Then I got warning about 2000 strong wave of tier 2 frigates about to hit my last captured world, the one with Hive Golem that I was desperately trying to repair in time. Seeing that I won't make it I started preparing fixed defenses there and concentrating my mobile forces to help. The Black Widow Golem was dispatched to help kill the smaller attacks a while back and I knew it wouldn't be able to come back in time. Just as I thought the crisis is over, I got warning about another 2000 strong wave to hit the same planet and things got crazy. I abandoned the defenses and went to galaxy view to gather more ships to that planet. And strangest thing I noticed - I was missing one planet (far right in the middle), then I noticed it was not one but two planets I lost (both neighboring the level 4 AI planet) and I was just loosing the third one - directly bordering my home world, which also happened to be attacked from the level 3 world bordering with it. So I abandoned the idea of gathering my ships scattered there and moved them to defend my home command station instead. But it was already too late - I lost all cryo pods and space cities
And then the combined 4000 wave entered the world with golem still being repaired there. They went straight for it and obliterated it in matter of seconds. Then they started chewing through my weakened mobile forces, while I was out of resources due to rebuild and repair effort carried out prior to the attack.
With many worlds lost already and couple other waiting in line to be killed, and more importantly, failing to protect the human remnants on my home planet - hope was lost and suffering began.
I don't really see that game going anywhere now, so I decided to finish it at this point.
I started wondering what could I have done differently and I think I should have played more aggressively - especially after Dyson Sphere started wrecking havoc on AI worlds. One of my concerns was that I had to destroy the Black Hole Machines if I wanted to progress without capturing some worlds, and that meant raising AIP - so I just left some worlds, only stripping them from warp gates, under AI control, especially the high level worlds. In retrospective, I think it would have been better if I captured all the infrastructure on AI worlds (Black Hole Machines and Ion Cannons) - it would slow down AI attacks, and the AIP would be slower than when I killed Black Hole Machines first to be able to retreat my forces.
But the Doormaster slowed down my expansion a lot, especially in the beginning and I had to fight through high level worlds just to see where is it worth to go to next. Scouts were just instakilled and never made it past those chokepoints, and transports were stranded by black holes - so I destroyed those just to see whats further down the line - that raised AIP and ultimately, caused a lot of trouble after I captured both golems. I think that if I could keep AIP down to Tier 1 longer, I could still get out of it alive...