Annulus app for iPhone and iPad

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.