Monday, February 17, 2014

Curvy Rhombohedron Skewb

The first couple solves I just started putting pieces together that looked like they needed to be put together. Eventually a 3-cycle or a twist or two needed to be done to finish up and I drew from my Skewb Family Arsenal of Algorithms (I just made that up).

But then Kevin asked how I solve the Skewb, so I got out the Skewb Cube and solved it. Then the Tetrahedral Skewb. Then the Squished Skewb. Then I intentionally tried to use the same strategy to solve the Curvy Rhombo Skewb.

Documented Scramble #1: DNF
After getting the first 8 pieces solved, leaving only 6 to go, the thing still looked scrambled! After using a setup move and the 3-cycle to place 2 of the 6 pieces, and not being able to see how to undo the simple setup move, I decided that although it is possible to solve in the same way, a more intuitive approach would be better.

Documented Scramble #2:
After solving the yellow layer, including the green and purple triangle center pieces, one twist of the black layer was needed to solve the 3 remaining triangle center pieces. That left the 3 remaining edges out of place and the remaining corner twisted. After using Double-EPS to place the edges instead of the pure 3-cycle, both of the diagonally opposite corner pieces needed twisted. I don't think it is possible to twist them together, so I twisted each one with a triangle using an algorithm that hadn't been used in any of the previous posts' solves. I will not even attempt to type it out.

video

So it turns out I not only demonstrated the algorithm. I also showed what happens when unexpected results happen, and one way to solve mysteries! :D

Documented Scramble #3:
Very difficult to get the yellow layer this time. The first several times I tried it this way it seemed almost trivial to get a layer solved. But this time, either it was a different scramble, or my mind wasn't in sync with the puzzle as before. This can be a problem when solving intuitively rather than with a systematic strategy. I ended up using Triple-EPS a couple times to swap pieces into place on the yellow layer.

After solving most of the black layer as described in #2, once again I ended up with the 2 small corners twisted. Two lessons to learn. First, if I would use the same steps as I do with other Skewb puzzles, I wouldn't have this problem at the end. So is it worth it to work through a more visually challenging solve at the beginning to make the endgame go more smoothly?

Secondly, it dawned on me that one conclusion I made in #2 above is incorrect. I said "I don't think it is possible to twist them together," because one is in the corner role and the other in the center role (thinking of the Tetrahedral Skewb). But what did I learn in the video above? I can twist 1 corner and 3 triangles, in the unshapeshifted puzzle, and 2 of the triangles are centers! So I can twist a corner and a center together! Yay!

video

In conclusion... well, is it ever really concluded? Let's just say that after several more solves I have decided that at this point I rather like solving it using the same basic approach taken with the other Skewb Family puzzles. That is, get the 2 small corners and the 6 triangles first. This only takes a few simple twists. Maybe 1 EPS. So with half a dozen twists or less more than half the puzzle is solved! Then 3-cycle the 6 big pieces home.

If a corner needs twisted without disturbing triangles, up twist down replace up twist-the-other-way down go-back works well and is pretty simple. Let's see.

video


Bottom line though, with this puzzle, as with any puzzle, there is no right or wrong, easy or hard, better or worse, way to solve it. I may decide on a favorite way to solve it tonight, but 6 months from now pick it up and take a whole different approach. I suppose I should demonstrate the Preferred Method applied to this one, so

Documented Scramble #4:

video

3 comments:

  1. What is the Double-EPS? How is it different than a 3-Cycle?

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  2. An EPS on this puzzle does a 3-Cycle plus double-swap. Doing the same EPS twice in a row does a 3-Cycle, and swaps back the other pieces, so it does only a pure 3-Cycle. So the answer to your question: no difference! But when solving skewbs, I sometimes use a 3-Cycle that is not a double-EPS.

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  3. Thank for the reply. Even though I wasn't entirely sure about what it was, I experimented using my limited knowledge of a 3-Cycle and figured it out much to my pleasant surprise and now I can follow along with better understanding. Once again, I appreciate the reply. And the good news in the end is that I can now solve the Skewb Curvy Rhombohedron puzzle. The important keys were the two algorithms you showed; one for cycling the edge pieces, and the last for rotating the remaining two edges. Thank again for the tutorial.

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