Tomorrow Challenge concept:
We tried to address the challenge in the lyrical theme of the song, and also in the compositional approach of the instrumental music.
Lyrics/Theme: the song is about the end of a romantic relationship, and how the narrator feels his life has been turned upside down from the happy days of the past to the misery of the present as he's dealing with the breakup in the moment. As an extra turn, the chorus suggests that the future could be brighter, i.e. another upside-down flip of emotions. The narrator was on the top looking down, now he is on the bottom looking up.
Composition: The song is in Am, with a chorus of Asus Csus F Dsus, Asus Csus Dsus F G. For the bridge, creating a change in feel and to be subtly in the world of the "Upside Down" as it were, we chose to use the concept of negative harmony (on the b3/3 pitch axis for Am) to transform the chorus progression into something that is based on the original progression but moves differently and hopefully slightly uncannily, compared to the original: Dsus Bsus C#m Asus, Dsus Bsus Asus C#m Bm. Additionally the guitar melody that plays in the instrumental breaks before verses start was transformed via the same negative harmony construct and plays over the bridge, the "right side up" version then gets played fully over the final chorus.
Here's an article on negative harmony if that helps, it's basically IMO just like a music theory trick for making music not only change keys but also invert the direction of the intervals so the new progression is still related in a mirror universe way to the original:
https://dantepfer.com/blog/?p=368
I'm sure there's YouTube videos on it, like a bunch of Collier videos or whatever, but I mostly referenced this article, any misunderstandings of the idea or bad execution are my fault alone.