I'm not totally sure it hasn't been raised before (I would be quite astonished if it hasn't) - but I was unable to find anything about it, so...
At least on my device game only get's saved right at the start of each turn. Whatever orders you give (buildings, ship movements, research, etc etc) doesn't get saved when you leave the game.
I mean...you certainly can get used it it - you just have to discipline yourself to always leave the game right after the start-of-turn-info-screen, but still I don't see why it couldn't get saved (again) when you leave the game.
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Btw: In the beginning it really made me hopping mad that you can't really save the game manually and have more than one game slot (as every other such game i played in the past had), but meanwhile I see the real charm in it. No redoing of bad decisions, no reloading til you get the desired outcome ...got to take the good and the bad as it's dealt to you. Kudos to you for that brave move!
Yes. Saved game is to start of turn only. Normal since day 1.
If you want to avoid frustrations this is how you can handle it. I play ST4x during my commute to/from work in the 30mins+ subway ride. I use a Samsung Galaxy S4 that locks after about 1 min. - If you know you are out of time, don't start the turn. - If you can finish all the players input, tap "End of turn" and put back in the bag (or whatever). I do this with my phone a lot and the turn usually get processed before the phone is lock. - Unlocking the device (for me anyway) will leave you in the game. Do not go out to other apps until you are done with game or you risk the game getting shut down.
Star Traders Elite
Age of Pirates Elite
Star Traders 4X Elite
Would be great to include this in the tutorial at least. Took me quite a while to recognize it (and I doubted my sanity a few times) - because my usual habit was to do everything I had to do, then leave/save the game and see the results and resulting actions next time I start playing.
If I leave the game open in the background on my Nexus 5, it will save mid-turn changes almost indefinitely unless I open too many other apps. It usually persists if I only open 1-2 other apps at a time.