Message #4080

From: Melinda Green <>
Subject: Re: [MC4D] 2x2x2x2 solution and analysis
Date: Sun, 29 Jul 2018 22:49:13 -0700

Welcome back Jay!

Unknown to most of the list is the fact that without Jay, perhaps none of this would have happened. Don and I had written the first version of MC4D some 30 years ago, but were at an impasse. The implementation was a bit of a mess, and neither of us wanted to clean it up, nor open-source it in such a state. Jay came along and said "I’ll do that", and did the dirty work needed to satisfy our requirements and get it to build on Linux. His help was a godsend.

Regarding video series, the solution to making them play in order is to create a playlist. You can reorder them, add descriptions, and then just share the playlist link. I’ve added you to the 2x2x2x2 HOF and linked to your scramble, but once you create a playlist I’ll link to that instead.

BTW, Jay’s solution is #10, the first-10 solutions list is full. As with MC4D, I’ll have to settle for the first-100.

It’s great to have you back, Jay!

On 7/29/2018 6:25 PM, Jay Berkenbilt [4D_Cubing] wrote:
> Hello all – this is Jay Berkenbilt, one of the longest time members of this group, and the second ever solver of mc4d back in October, 1998. I’ve been mostly lurking on this list since its formation, popping up every now and then. Several weeks ago, I ordered my physical 2x2x2x2 puzzle and then sequestered myself to do my own analysis and solution, free of spoilers from the list. I have completed this, and I’m now ready to share my work, dive in, and join all the discussions. I’m looking forward to contributing and learning.
> I have created a YouTube channel <> with my solution videos. You should view these "oldest first". The videos are numbered in order and also linked below in order. Clicking "Play All" will show you my videos in reverse order. I don’t know how to fix that.
> My solution method is as follows:
> * Do a full scramble
> * Get all the blue and green stickers off the corners – some will be on and some off right after full scramble, and the next stage works better if they are all off the corners
> * Get all the blue and green stickers onto the corners starting from all of them off the corners
> * Solve the blue slice
> * Solve the green face as much as possible; sometimes there will be a single corner out of orientation or a pair out of orientation such that one can’t be rotated using regular 3D Rubik’s cube moves
> * Resolve the final corner orientations
> It typically takes me about 15 minutes to do a full solve. I tend to do things in a fixed order rather than doing much exploitation of things that coincidentally happen to be in an ordered state.
> I have created a series of 11 videos, each ranging in length from about 2:30 to just under 10 minutes, but most are in the 4 to 8 minute range. The videos are as follows:
> * 00: 0:39 personal introduction <>. You can skip this unless you’re curious about who I am and what I look like.. :-)
> * 01: 5:18 mapping to mc4d <>. This is my discussion of how I map this puzzle to the software mc4d puzzle and how I label the slices.
> * 02: 9:19 gyro <>. My "gyroscopic rotation" video. Here I present my algorithm for the 4D rotation that moves some other slices into the top and bottom positions. I describe in detail how to look at this and how and why it works. My sequence is different from the one in Melinda’s introductory video and requires only five moves with no "cleanup" moves.
> * 03: 4:06 scramble <>. This is the full scramble I used for the solution. I’m using a previously posted method for scrambling, but I describe from first principles why it is valid.
> * 04: 7:59 blue green off corners <>. First solution stage: moving all blue and green stickers off the corners. I also introduce a few move patterns I use systematically throughout my solution.
> * 05: 6:14 blue green to corners <>. Second solution stage: move all blue and green stickers back to the corners. It turns out in this case to be all but one, which happens sometimes.
> * 06: 5:02 solve blue <>.. Solve the blue face starting from all the blue stickers on the outer corners.
> * 07: 3:53 green except last corners <>. Solve green down to one pair of corners out of orientation such that one of them can’t be fixed using regular 3D Rubik’s cube operations.
> * 08: 4:08 final solve <>. The final solution, resolving the pair of non-oriented corners (or "disoriented", as I say in the video), with a clear explanation of how my method works.
> * 09: 6:00 corner monoflip demo <>. A stand-alone video showing my algorithm for fixing the single corner monoflip issue. My algorithm is 34 twists, counting twists of a half slice (treating one face as a 3D Rubik’s cube) as a single twist and counting the gyro as zero. (One could argue that the half twist should count as two because how it is justified, but I’m counting it as one here.)
> * 10: 2:30 pair swap demo <>. A stand-alone video showing a common sequence I use to swap two pairs of corners. I use this various times during the solution (contrary to what I say in the video), but this video demonstrates it in an otherwise pristine puzzle, making it easier to follow and understand.
> Each video has a descrption with slightly more detail. I hope you enjoy these. I’m looking forward to feedback and commentary.
> –Jay