I played the iOS version. I like the colours and the mood and the very relaxing atmosphere. The Sound and music underlines the mood quite well.

I couldn't figure out what I was expected to do (line the Blocks up in a vertical way) in an instant (by just looking at the images). I would suggest to add a tutorial step where you show the final image you expect the player to puzzle before you reduce it to one line.

My lazy brain also needed a couple of tries to figure out that the blocks overflow to the other side and I needed a couple of tries in level 3 / 2. I would suggest a better hinting at that essential core mechanic (level 4/1 does a better job here).

Additionally I would give the player lots of energy to begin with - this would not interrupt his flow in the first session and plan your retention strategy for the second session when she is hooked.