I have finished the pack. Here is my entire replay collection for the pack. I also did an LP of the pack. Link is here:
Kaywhyn's LP of Niesch's Yippee! More Lemmings. Enjoy!
Feedback on the PackEven for a 20 level pack, this pack is not a quick solve at all. Total time to solve the pack was about 6 hours. Pretty much all levels after the Fun rank gave me a challenge in some ways, although there were still some easy levels in the Tricky, Taxing, and Mayhem ranks. In the Fun rank, I say the hardest was Fun 2. This level is the first real puzzle after the very easy Fun 1 which is a 5-of-everything level. Since it is a really small level pack, it makes sense that the first puzzle level would be this early. I still really like the level a lot, though!

Fun 5 definitely reminded me of Painless 1 from Lemmings Migration in that I still ended up struggling for about the same amount of time on each level. Honestly, I think it's a psychological thing when solving levels via LP. I likely wouldn't fumble my solutions as much if I had solved on my own off-camera. Then again, I don't mind the occasional silliness in my LPs, as I'm trying to also be entertaining while solving the levels. After all, I think LPs should be like that, since viewers are watching how someone else is solving their levels and hearing their thoughts on the solving process, and being entertaining from time to time in an LP is always a plus.
Once you get into the Tricky rank, I say there is somewhat of a jump in difficulty. This is evidenced by how I still ended up struggling with Tricky 1. I definitely had the solution, just couldn't quite get the beginning to work out the way I wanted it to when holding the crowd back. My favorite level of the rank was Tricky 2. I absolutely loved the
blocker turning a shimmier around trick. I honestly have never seen this shimmier interaction before, even though I have played so many shimmier levels before I played your pack. Nevertheless, I was able to figure out the trick on my own. I think it came to me while contemplating, "I need a way to turn the shimmier around." I think that's where I had the idea that the blocker had to be the answer.
I also really liked Tricky 3 a lot. Really nice 1-of-everything level that took me a while to figure out but in actuality isn't too hard. I like the solution a lot. Tricky 4 I wasn't too much of a fan due to all the fiddliness in the execution. Finally, even though Tricky 5 needed multiple videos, I still somewhat liked it. It looks quite intimidating from the very tall size of the level, but is not that hard either. The really small skillset means there aren't that many options available to try in the level, and so it doesn't take too long to stumble upon the solution.
The difficult puzzles continue with the Taxing rank. I say the hardest level in the rank is Taxing 2, with Taxing 1 probably a close second due to the puzzle and to an extent the time limit. Taxing 2 is the only other level in the pack that needed multiple videos, but luckily I was able to figure it out. It's really all about finding the most efficient route while conserving your skills as much as possible to ensure you have enough to get to the exit in the end. I say the most difficult button to get to is the one at the very top. Taxing 3 wasn't too bad, although I initially thought it was a bit unfair due to how the timing of catching the bottom lemmings is too tight. Turns out it wasn't as tight as I thought it was, perhaps due to my builder/platformer placements. Other than that part, it wasn't too hard of a level. For sure my favorite level of the rank is Taxing 5. Very nice solution, and you can even tell I was having fun with putting the lemmings in the form of characters from the movie/novel Tarzan. I called the bottom lemming Jane because of how much immediate danger that lemming is in, while the top lemming is of course Tarzan. It was initially a hard level, but once I figured out the first shimmier usage the rest was easy.
Finally, for Mayhem I must say that the levels in the rank were easier than some of the levels in earlier ranks. There wasn't really any level that stood out to me as very hard, but I would say the hardest in the rank was Mayhem 4, with Mayhem 2 probably a close second for hardest. I might had ended up backrouting Mayhem 4, though. The only hard part is the start, but after you figure out how to stop them from being in any danger, the rest of the level is somewhat easy. I do have a stacker leftover, though. I absolutely loved Mayhem 1 due to how the level title makes a reference to the mathematical theorem. I'm a math person, and I happen to be a math teacher, so I very well know it refers to the Pythagorean Theorem. The level itself is very similar to the Just a Minute levels from the original Lemmings. I also really liked Mayhem 3. Probably the easiest level in the entire rank. The solution doesn't take too much thought at all. Finally, Mayhem 5 is far from being the hardest level of the entire pack. It is difficult, but I think the hardest part is figuring out how to use the builders and avoiding the fire traps. Builders may be plentiful, but they surprisingly run out fast, and I ended up using all of them.
Even the two Bonus levels weren't that hard. I absolutely loved the design of the levels, though, especially Bonus 1. I love the lemming sprites in it. The only one I'm not sure about is the far left one. Is that supposed to be a bomber in the ohno animation? Bonus 1 still ends up being somewhat difficult, but is still easier than Bonus 2. Bonus 2 is hard only because it can get very overwhelming with the huge flood of lemmings everywhere and the several splitters that send lemmings in different directions and places. Nevertheless, there's not that many skills at all, and so it doesn't take too long to figure out where the skills go. It's still not easy to figure out where they should go, though. Before I made serious attempts at solving, you can see that I first decided to let the level play itself out without doing anything to see how many actually make it home before time runs out. Close to 200. Then I slowly used the skills 1 by 1 to see how much of an improvement or non-improvement it makes. When I just used the stacker where it was placed in the level, it made it worse. It's really just a matter of determining which splitters to avoid and keeping the specialists with their own group, i.e, floaters with floaters and gliders with gliders.
Overall, this is an excellent and very well-done pack. I absolutely enjoyed playing this pack a lot and especially the challenges that await within. When I had Tricky 5 as the first level in the pack where I needed multiple videos, I started to worry that said level and later ones would get too hard for me to figure out and solve in a reasonable amount of time on-camera. Luckily, I was able to figure them all out on my own, albeit with a lot of struggling on certain levels. The video lengths still ended up being an improvement over the ones in my 2 other LPs. Still, I can work on cutting down the lengths drastically.
With all this being said, I absolutely agree with your assessment that you were trying to make not a very hard pack but a challenging one. I believe you have succeeded in this regard. There were still some tough nuts, but none were over the top hard. I also thought the pack challenged me appropriately enough that I was still able to enjoy playing it. The pack sometimes did get overwhelming, but it wasn't bad enough to make me think about what I had gotten myself into. I guess beating your pack is redemption that I wasn't able to figure out your R1 contest level. I was able to figure out the rest. I'll get your R1 level one of these days, though. I'm sure it's a level where you at first need to keep the crowd going before containing them.
Again, nice job with this pack, and I can certainly highly recommend it!

If you're feeling up for it and think you can handle this, go for it. You will love the challenges within
