Nice game! Somewhat reminiscent of agar io.

I think that the best part of the game, as others have mentioned, is the music! It really adds more of a sense of progression to the game, plus it's catchy! 
Feedback wise, I would recommend that you take a look at vertical systems and their implementation. Right now, if the player reaches the score threshold for the next layer to be added, it seems like you just change the track for a new one, so the musical phrase can be interrupted and you go right back to the start, which can be a bit distracting. If you're using only Unity and no audio middleware, what you can do is have all of the layers playing simultaneously in their own AudioSource, and route each one of those AudioSources to a separate Group in the AudioMixer.  You lower every group's volume except for the first one, and then make Snapshots for each state (layer 2 added, layer 3 added, etc). You then transition to those snapshots when reaching the score threshold, so the result is a nice fade in to the new layer without interrupting the current loop. It's less efficient in terms of computer resources, but I don't think it would be too much of a problem!

Keep up the good work!