I like the art style and near monochrome colour scheme used, and the music was fairly relaxing. This was a great decision as it didn't feel distracting.
The variety of puzzles was good, and the difficulty felt consistent all the way through. Each puzzle felt reasonable, and the length of each puzzle was short enough that I felt encouraged to try different ideas, and then restart and quickly get back to a particular spot if a particular action didn't pan out.
The controls and mechanics were fairly intuitive after the first few levels.
It is a well designed puzzle game.