That is rather difficult, but the merit in all things consists in the difficulty.
-- Aramis

Let's try Level 3

First trial

Pressing Ctrl+3, we have this:

Well, after a few wild guesses, it just becomes a mess. I have no idea on how to solve the puzzle from the state yet. Pressing Ctrl+Z to the beginning, and git it a try again:

That was a lucky solve! Patterns and clusters naturally emerge in the last few twists, but the first few twists were just lucky. Still, let me try to explain why it worked.

The reaosn that level-1 scrammble looks obvious to solve is that there are at most two or three colors in each cell, as a 4-cubie cluster or 2-cubie cluster for each color. This makes things simple. As level goes up, the situation becomes messier, but here in level 3, we still don't see much lonely colors. We still see many 2-/4-cubie clusters. Among them all, blue and pink are the exception.

For some reason, the right-hand side of the center cell consists of 3 blue cells and 1 pink cell. Also we notice that, the bottom cell consists the opposite: 3 pink and 1 blue. Ideally, the near we are close to a solved 2x2x2x2, the more 4-cubie of a same color we should find. The 3+1 combination is complex, but maybe we can amend a 3+1 and a 1+3 together in a cell, and then do something to make it a clean 4 pink and 4 blue cubie cell.

With this in mind, first we twist the left-back cell so that the left-hand side of the bottom cell comes up to the center. In the second and third twists, I demonstrate a way that eventually works. By intuition, I was just looking for the way to twist the centor cell and meanwhile make other neighbor cells closer to the solved state, by making larger color clusters.

Compared to the first failed attempt, it wasn't really that much difference. Instead of dealing with blue and pick first, I went with yellow and light green, but unfortunately, I didn't find the right twists, so it ended up a mess.

Second trial

Let's try one more,

At the first glance, the left-front and the right-back cell looks chaotic, but as you read them carefully, we can transform them into 4 2-cubie clusters in one twist. The twist also help with other cells,

Now we can find that, the left-front, the center and the right-back cell are all made up of 4 clusters. The left-hand side of the center cell has blue and pink and the right-hand side of the left-front cell has blue and pink as well. This suggest us the next move,

and then it becomes obvious,

Conclusion

Thanks to the GNOME desktop, which provides a embedded screenshot utility that powers my playthroughs so far, but there are bugs like not showing my cursor and sometimes just not recording. I should find some alternative in the future. Also thanks to CloudConvert for transforming those video clips to gifs.

For the readers, I cannot imagine what's your feelings about the puzzle and my naive analysis. It looks like nothing, but it does require a huge effort to establish the mental model. Hypercubing is far from just playing around with color cells, and it is deep by definition.

With basic 3D twisty puzzle experiences and the preliminary level-1/-3 playthroughs, I would like to dive in to a full scramble directly. As declared, this is the core of Part II. For the record, I haven't solved 2x2x2x2 before. Hopefully I can make it in the end of Part II, and introduce my solution then.

小結

解決了難度三等級的挑戰，明日開始進行正規挑戰。