Cast U&U

5 

This puzzle is a difficult one but after enough time you will figure out the mechanics behind it. You cannot solve this without learning how it works, but dont let that discourage you. You'll inch your way around learning how these pieces seperate in no time

5 

Very good - gives a good run for the money and like others have said, more like a level 5. I own all level 4-6 and I recommend this one.

5 

One of my favorites, partly because it appears to be just a few pieces of familiar hardware, partly because of the solving method. This puzzle is much more complex than one might suspect at first examination. There are several Hanayama puzzles that disappoint because it is possible to stumble onto the solution by just fiddling around with it. That can't happen with U&U.

5 

Wonderful puzzle! I think it is very beautiful, original, logical and great! Definitely one of the best Hanayama puzzles! Not for beginners, as previously mentioned before me, nor for people who count on good luck only.

3 

Found it more grueling than enjoyable. As previously noted - not smooth, doesn't feel like Hanayama puzzle at all. Other Hanayamas I have each has its own character and appeal, which makes them a lot more interesting to play with. This puzzle may have smart solution, but it just looks graceless. It's harder than level 4 for sure. More like 4,5-5. I would not recommend this puzzle to be your first from Hanayama series. There is a chance that you might not want to buy next one.

4 

This puzzle is clever. It's impossible to separate the Us by luck or any unintentional movement which is great. As one can guess from the design, it doesn't have that elegant flow typical to most of Hanayama puzzles, it just works in a different way - lots of adjustments and tiny movements (sometimes little bit forced) included. I found it a little bit more difficult than typical level 4 puzzle (Marble for example). The time you need to visualize the sequence of movements is comparable to Elk. Took me an hour to solve it and one more to fully appreciate the design :) Still quite fun to play with it afterwards. It's not that kind of challenging puzzle that you can hand over to someone and watch them accidentally find a solution within 10 minutes or so. Nope, ain't gonna happen!