It's built in Unity. For the music, I created a basic "Score Manager" that chooses from 1 of 3 different pieces of music depending on your current morale, so as things get worse, the music gets darker and sadder. It's pretty rudimentary, but I think the effect works pretty well.
Code is available here, if you want to take a look: https://github.com/tonyrobots/penguinexpedition/blob/master/Assets/Scripts/Score...