Hi Paideia, thanks a lot for having played our game, we're happy to hear that you had fun with it! :D
Regarding the music, I definitely second your thoughts... The fact is that we both kinda suck at sound design, and music is usually the last thing we rush to put in the game ^^" But we're going to follow your precious suggestions for the future: for instance, I never thought about using an ambient background to match the tone, it's something new for me and that's exactly what we need from feedbacks! Thanks, really! :))
The information about what machines produce in the next levels is always accessible from the cards, by clicking on the text "Lv X"... However, we know that this possibility is not made clear in the tutorial, and every player misses it :( It's not your fault, we'll definitely improve the UI in the next update!
About the end, it's nice that you managed to escape with not so many difficulties. You're right: once the production engine has started, the game becomes pretty easy (...without malfunctions). We wanted to keep it affordable to everyone because it's our first attempt with "management" games, and balance is not immediate. However, one of the ideas for the future was to have more types of resources, making the machines unique in their production, exactly as you suggested. But that's for the another day :)
Again, thanks a lot for your helpful feedback, we really appreciated it!