Made it to level 9 with a score of 349

Overall the visual appeal appeared to have made my retinas tired while at the same time was a bit hypnotic giving the game a bit of a challenge when things started to speed up. The music was fantastic, though I would had made the music fade in and out of each other when songs played so there would be a subtle change. Over all not bad of a game.

The music is currently the best feature of the game, don't change it. I assume it's supposed to be a relaxing game which the overall sound covers pretty decently. In terms of originality I can't say much, it's a faller game like others before. But I liked the execution, in other words the idea of staying between light and dark. Seems to have a somewhat philosophical approach to it, but maybe you can expand on that to distinguish your game further. For the graphics part I'd like it better if the changes between light and dark would be more fluent. First time the screen turned from dark grey to light grey I assumed this was the "light" I was supposed to stay out of. Maybe implement this effect over a longer period and with more subtle nuances. I would also like it better if the top of the screen wasn't yellow, doesn't seem to fit the overall design, but that's just my personal liking.
These are all just minor issues. What really needs some tuning are gameplay and gameplay mechanics. As I said, I liked the relaxing feature of the game which is supported and mostly carried by the music. Now I don't know if the levels are somewhat created randomly since I only played it once and don't plan to do so again in the games' current state. Still, my suggestion is to skip the first five to eight minutes of the game which don't pose even the slightest challenge to the player. Or at least shorten the duration of the levels to one or two minutes. Only rolling from the left to the right and waiting for the screen to catch up isn't really relaxing but kind of boring. Around level 7, respectively after 8-10min I had to check up on something else. It was kind of a pity since the game had just started to get a bit more interesting. At this point, a Pause function would be of great help.
I was afraid that there might not be scores and such, but you surprised me. However, there is no connection to a scoreboard and the like. Now I don't like posting score in the comments. This is about your game, not how well a player did. But to seize upon that idea, it would encourage players to visit the game more than once if there was some way to compete with each other (i.e. a scoreboard function. Also, medals always motivate;)
Still, all of this wouldn't be enough to motivate me playing "The Lonely Descent" again. The main reason is that it takes forever to pass the first levels. I checked, after dropping the ball you start all over again. Here, a pass code option or an auto-save every five levels would greatly increase the motivation to play again.
One last thing about the mechanics/physics. I like how the ball is floating from top to bottom, that is actually relaxing. But if you stopped that floating feature at the moment the ball makes contact with the ground, it would make a great contrast. What I noticed was the ball spinning into the direction it was moved as it should be. But the delay until the spinning changed directions gave the world a somewhat "icy" feeling, like somehow the ball slithered over ice. Would be great if you could make the changing of directions more corresponding to the spinning of the ball, which would seem like more traction and add a contrast to the floating of the ball when in the air.
All in all, it was an interesting approach to a faller game with really nice music, but the gameplay and mechanics need improvement. Maybe add some features for competing or other stuff that usually makes games more "addicting". Or maybe expand more on the philosophical approach and make it more of an artistic game. You already have a good foundation with the music. Maybe add a story to the game or a more easily relatable overall statement. I'm sure the other developers can help you out with some of the issues. Still a good attempt.

The game is relaxing and goes at a well-judged speed, but the graphics were a bit limited. You could still have a "soft" and not too "busy" feel with some more interesting graphics - perhaps some kind of design motif ... or perhaps a motif that changes as you progress through the levels (for example an organic/plant-like design, or one that incorporates geometrical patterns).

The music was not so relaxing, didn't seem well-matched to the rhythm or pace of the game, and was quite annoying. But one can always mute it :)

The speed of this game is good. It didn't fall into the trap of moving so fast that impossible situations were caused, as this type of game usually loves to do. There is not really a lot of meat to this game though.

This game needs medals.