I think there might be a problem with the alien AI. If not , this can be a good strategy for getting an advantage. I recently played a game where I expanded very fast close to the AI. They managed to capture 5 or so settlements. They tried to get a sixth, but I kept destroying their colony ships. I settled one of the systems towards which they were trying to go. and tried to guard as many settlements I could so that It wont advance too much. But he kept sending colonies in the same place even if there were unguarded planets on other directions. This might be a sign of the Ai lacking After a while he stopped even trying. I basically cornered him and he remained with 6 settlements.
This was on hard, 64X64 and 64 planets V 1 Alien. I can post screenshots of the middle game whole map situation if you want. I can describe the general order and my approach to the game. The game Is pretty much won now.
Nexus 5, android 6.0.1. I can try to share a screenshot form my phone later today.
On another note, here's an update: I tried a game on PC as well. Here's what I noticed: On android, when for example I attack a colony ship and hit it, usually the colony ship will not be able to move more that 1 space next turn. I though that was a mechanic. I would stop it from colonizing a system I wanted for example. The ship keeps trying to get there besides my ship blocking it(I also noticed It usually only goes to adiacent squares, never on diagonal. I might be wrong though). On PC on the other hand, the colony ship just passes by my ship with no problem.
The only screen shot I have is with the mid game situation after the AI is surrounded. I'd be happy to share that If it helps.
mikell - any screenshots would help. We'll see what we can find with your information, but the more details about exactly what tactic you are using against the AI would be most helpful -- then we can improve!