Mini Metro is a game elegant in its simplicity. That's why it could have easily been created on Newgrounds. In flash. For free. I'm not saying that this isn't a good game. I'm saying that it's the equivalent to some of the less impressive browser-based games out there, and in an era where there are some truly fantastic pieces out there for three dollars or less, the asking price here is akin to extortion. It's not worth your money. Seriously. Just go on Newgronds. You'll find better games that you don't even have to pay for. Chalk this one up to yet another GoG game ripping people off.
I played this game elsewhere and let me be blunt with this review - Don't waste your time. The mechanics of this game are deliberately set up to make your choices meaningless. At any given point in time, there is one, and only one, right answer. Even if you know what skills you need, you'll fail if you don't train them the right way, or in the right order. Sometimes even though you focused on a skill well before you needed it, arbitrary restrictions will mean you still end up with it too low to pass the check. So your entire game will be filled with failing meaningless choices that amount to nothing...and they do amount to nothing. Often, you'd get the same results with a failure and a choice as with a success. In fact, succeeding checks can even open up new ways to fail rather than making you more likely to succeed. Factor in the princess' personality and ignorance, and...well, if you can get through even a single play session without loathing her and wanting to send her to the headsman yourself, you have more patience than I.