I've always loved these music-based games when you could only lie back and listen: aim for the goal and avoid several 'bad notes'. Here, its as simple and calming--easy on the nerves--and the animations are fluid and smooth. The usual flexible hit-boxes for errors and scoring add to the simplicity.
Though I think the circle-draw limit for combos should be known. With the shop purchase, its a maximum of five possible chances for combinations. I only found this out later in-game after a couple songs or two.