Umbrella Irony - Yes, these are the kind of levels from Save One I like! Once you figure out that you can't afford to use any skills getting past the trap, the old umbrella compression technique comes to mind, though it probably took me longer than it should have

Aquarium Deception - The old adage 'just because you can doesn't mean you should' springs to mind here. I kinda hated this level, to be brutally honest with you. The fact that it's a nuke solution occurred very early on after realizing you'd need 16 builders for an easy solution and you only provide 15. The one-pixel gap at the top of the central structure isn't that hard to spot, so the nuke solution was readily apparent. Pulling it off though, jeez. I actually had to ask another member with more experience of the mechanics of the game than me exactly how nuke counters work and even armed with this knowledge it was a pain and a half to execute, bunching up the back of the pack, keeping the first lemming out the hatch busy while the back of the pack catches up. Yes, this is possibly the hardest level of the pack but that difficulty doesn't really come from problem-solving, it comes from timing and pin-point execution, which is something I don't like. No way I could be bothered with going for the talisman solution after all that, which no doubt would have been fiddly as heck.

Clappy Clappie - Pretty sure I backrouted this one as I saved a lot more than 1!

Clues Do - My favourite level of the rank. A clever little puzzle that took me a while to see how to get a non-climber over to the ramps. In the end I went for a climber compression technique, which was quite hard to pull off in terms of timing, but a satisfying level to solve. Nice one!

Blues - Oh great, another nuke solution. Two of em in a 6-level rank is pushing it. Needless to say I wasn't keen on this one either. The fact it had to be a dreaded nuke solution occurred early on when I realized there simply aren't enough destructive skills to get one lemming down to the exit. I don't dislike this as much as level 2 because the timing and execution isn't so critical; the hard part is working out how to get the crowd down near the exit and contain them there. I think this level and 2 are the only occasions in all my time playing Neolemmix where I've had to make use of the right-button marker to keep a particular lemming highlighted! I'm not gonna say this and level 2 are unfair - quite - but you do need to know exactly how nuke counters work and I didn't, despite being a pretty experienced player. I ended up saving 3, more by luck than judgement I hasten to add, but I don't think it's a backroute because there's no other way down, is there?

The Blue Pi Oh, this was clever! I bore in mind the opening text saying 'This is not a Lemmings level' and after messing around fruitlessly for a while, decided I would just try deploying the diggers on 'S', 'A', 'V', 'E', 'O', 'N', 'E' and the final symbol and just watch it play out! Sure enough, it all syncs up perfectly and you can just sit back and admire your level design

Sweet 1 - Basic brick Nice level to start off the pack with a very nice save all optional challenge!

Sweet 2 - Falling down the stairs You'll be fine as long as you accept the many unfortunate losses here, as there's nothing you can do about the ones that get trapped at the bottom.

Sweet 3 - Long road to nowhere Can be challenging since there's no way to hold back the crowd, but you do have the necessary skills to avoid both of the traps. It's a matter of clearing obstacles as you get to them in order to avoid too many unnecessary losses.

Sweet 4 - Wish upon a Lemming Nice open-ended level with another great save all!

Sweet 5 - Just relax... As long as you know your stoner mechanics and realize you need to build over both the first and third gaps, you'll be fine here. I'm definitely surprised this managed to stump Guigui, but here I acknowledge that it's simply likely due to him not being well-versed with stoners.

Sweet 6 - A Puzzle Adventure Nice level to finish off the rank! I'm not sure if anything's changed here from previous versions, as I did take a quick look at the level after Pieuw posted not being able to solve this one, which I don't think is difficult. Again, it's due to him not being used to the new portal objects that were added in v12.13 NL.   

Sour 1 - Back again? Excellent level to start the rank! Love that sending two climbers ahead, one to build to the exit for the others and the other to turn around to bash the OWW to free the crowd, with the added twist that you need to time it correctly so that the first climber doesn't get blocked by the builder staircase and therefore will prevent him from coming back to the crowd later on. Well done!

Sour 2 - I need some space... Definitely the hardest level of the pack IMO, as it took me a while to figure out the solution. Another very nice level and one of the best of the pack! Nice use of the blocker to compress the crowd but with the added twist that you must release them before everyone falls out of the entrance so that you can bash through the first diagonal terrain before you lose too many from falling out the wrong way. Well done here as well!

Sour 3 - Chasm Capers Open-ended level and very interesting there's 2 of everything except for builders where you have 60 I'm not sure if the level is supposed to be harder than this or if it's simply anyway you like and that you just need to be quick before you lose too many Lemmings.

Sour 4 - The Ball Pit Excellent level! That jumping the penultimate gap to dig and then bomb in order to have the final builder go all the way through to the exit platform without getting interrupted is quite clever.

Sour 5 - Through thick and thin Another excellent level! Jumping over the gap and exit and mining from above along with bouncing off a blocker to free the crowd from below for the solution is really nice And of course that shimmier, I love the shimmier skill a lot in NL

Sour 6 - The Institution This definitely reminds me of a past contest level of The Tomato Watcher's which was kind of one that failed because it was backroutable IIRC. It seems way more solid here. Nice level to finish off the pack and not too difficult to figure out since you don't have that many options at any moment. Nice added touch with the final builder to the exit and then using the walker skill to turn him around to bash and release the crowd.     

Lems Are Playing Freeze Tag – I hoped this level would help you get used to the slider mechanic for the upcoming more difficult slider level.(Watch your step... )

Lighter Than a Snowflake – Looking back now this level might be a bit too difficult for where it is placed. I've received similar feedback from several people.

23:58:30 12/24 – The idea behind this level was: can you make a level with a single hatch and n exits, with a time limit that only allows a solution if you go for all n exits? The answer turned out to be a relatively easy "yes".

Lost and Found – I wanted to give some spotlight to one of the least-used skills: the stoner. You can create terrain mid-air without any starting point for constructive skills and that's a unique feature of the stoner!

Claustrophobia 2 – A spiritual successor to my level Claustrophobia from the previous Xmas pack. The urgency created by the tight timer is completely intentional!

Happy New Year! – Just for your information, several levels were co-authored. The general rule is: the first author listed creates the terrain/objects and the second author creates the solution.

Living in a Fairy Tale – This is my favorite tileset.

The Bear Necessities – Not exactly intended, but your solution is actually better than my original one!

Walking Bearfoot in the Snow – Yes, I didn't want to add too many extra elements beyond the main idea of the sacrificial jumper.

Sky Shield – I think you could have solved this level even without the hints!

Watch Your Step! – The theme I had in mind was that all skills must be provided as pickups similar to rule #3 in the current level design contest.

Warm Cozy Basement – I'm glad you liked this one. It's my personal favorite level in the pack!

Constructus Interruptus – Yes, this level stands out a bit in terms of difficulty. I could have removed some tricks to make it easier but ultimately I ended up liking them too much and kept everything as-is.

Where Angels Dare – Yes, this one is more of a visual level. I drew the scenery first and the solution came afterward!

And They Lived Happily Ever After – If this level made you laugh, then it achieved exactly what it was meant to do.   I didn't have any particular reference in mind when choosing the title.