In the Middle of Bubbles: The bubbles are clearly represented here and I think it opens the track very nicely. The soft piano with subtle strings feel so calming and would keep me at ease through this beginning part of the game.
Where no Bubble dares to dwell: The dynamic contrast and dark harmonies lead to a very ominous feeling in this area fitting the setting very well. The cello line is beautifully written and stands out when placed so bare in this composition with the accompaniment doing more decoration than foundation work. The lack of extra sound is a nice effect juxtaposed with the bubble sounds from the previous track.
Interlude: This is a nice little musical break. I think it was a great idea to bridge the contrasting styles between the dark track preceding and jovial track following.
Origins: I think it is a testament to your compositional style that even though there was a lot of energy up front, I felt that the climax of the entire OST occurred at one of the softest moments.
Overall: Silence and pianissimo were your friends in this soundtrack. I often have trouble knowing when to back off and am often afraid to do so. You leaned into it here and it paid off because you were able to create some really striking imagery with very slight instrumentation nuances. Well done and thank you for sharing!