NevoSoft Magic Rings

In 1960-70s an amusing plastic puzzle was invented, which consisted of two rings filled with coloured balls. It got many names in different countries: Eight, Colorful Beads, Eternity, etc. It was easy-to-understand and very interesting. It became extremely popular in a comparatively small amount of time. Some people spent days and nights untwisting and gathering again the magic rings. Anybody could easily master the game. But it was rather hard to solve the puzzle, although it didn't seem to be so. We offer you a computer version of this puzzle, and plus, more than 25 variants of it! Levels variate from elementary, which even a child can solve, to complicated, which demand a considerable time to be spent over them. An acquaintance of mine, a professor of Mathematics, spend 7 hours over one of the most difficult levels. But he was a success in the end. I wonder if you could do the same!