Hi there. Thanks for the reply.
That actually sounds heavily against the DRM-free nature of GOG -- there is no way that a single-player GOG game should ever require online access for any reason.
Can you please clarify whether the game is capable of saving offline?
Sorry, I'm spreading incorrect information. I spoke again with the dev team to clarify the specific changes we made for GOG.
Independently from the platform the game saves on Windows in the following folder: C:\Users\<Username>\AppData\Local\Mipumi\TLS\
Could Saving is not used for GOG. My bad, I should have checked with the dev team first. So you don't need an internet connection to save the game.
There is an optional use for internet connection though regarding the decision menu and the statistical percentages overview. But that's optional, you don't have to use this feature.