Good news: patch 1.0.1 is live.
* custom music is fixed (thank you Viperys for your help debugging this!)
* it's now harder to inadvertently reset the game... now you have to press both app buttons at once to reset (app button is above trackpad)
* other small improvements
I will still be adding volume sliders in an update soon so that it's easy to use a standalone player, but for now, your music as ogg files should work!