I feel like the volume mixing can be a little wacky at times. Some songs are really loud while others are really quiet. to the point where it feels like a mixing error more than a stylistic choice.
Having multiple tracks for the general gameplay is nice when thinking about an actual game. makes it feel more like an OST.
The final song felt really strange because of the vocaloid alongside the toy piano and awkward tempo. It didn't really feel like an ending song to me.
Overall, I think the ideas here are great, but the execution of some of them in terms of mixing and theming could use a bit of work.