It is an addictive puzzle game inspired by the mathematical concept of annulus. Annulus (the Latin word for "little ring") is a ring-shaped object, especially a region bounded by two concentric circles.

Challenge is to combine similar rings/annuli and complete the circles.
- Swipe left, right, up or down to move all the rings/annuli in the same direction.
- Same-sized 'blue' rings/annuli merge to form a larger 'green' annulus.
- Same-sized 'green' rings/annuli merge to form a larger 'blue' annulus.
- Two max sized blue (or green) annuli complete the circle.

Play tactfully to hop through different levels and unlock donuts. Each donut reward requires certain number of blue/green circles.