Nicely done! I'm glad to hear you found the levels design and mechanics engaging.
As for the music (or lack thereof) I originally wanted to add some main background music, but I couldn't come up with anything I felt fit the game in the time I had left so I decided to leave it silent. My thought was that the silence would have a "zen" sort of focus effect versus having a short loop which might become grating as the player plays through the game. So maybe in your case my decision worked out, lol.
In the end I came up with the end screen music in about the last 30 minutes of work I did on the game as I wanted to have the game end on an upbeat feeling once players had cleared all the levels.
Thanks for your feedback and thanks for playing!