Dodochacalo and I are happy to finally release our collaborative levelpack!
It contains 80 levels - 30 by Dodochacalo and 50 by myself - divided into 4 ratings. Our work spanned over a decade with lots of large gaps between short productive frenzies. Our main goal was to try and innovate while staying classic. We mostly used original tilesets, skills and objects, but tried to make levels that would feel fresh, puzzle-wise and/or layout-wise. There are a few exceptions of course, some new skills or objects may appear here and there.
We initially wanted to make 50 to 60 levels each but since we were making slow progress we thought better to release it now than wait another decade
We had to compose the ratings with what we had and that's why the difficulty may be bumpy at times. This being said, the pack may get updates in the (far) future with new content. 
Now for a quick presentation of the ratings:
1/ Incipio (~ I begin)
Note: There are only a few levels by Dodochacalo here but don't worry, some gems are wating for you later.
RELEASE THE KRAKEN!
2/ Proficio (~ I progress)
Latecomers
3/ Scando (~ I climb up)
20,000 Lems Under the Sea
4/ Impero (~ I rule)
Itinéraire Touristique
Some people here already played my levels. You'll find them mostly unchanged here except for a few tweaks and backroute fixes. The main change I made is that I removed The Architect was on Acid and replaced it with another mystery level somewhere in the pack.
We hope you will enjoy these levels! Any feedback is of course appreciated, and replays (even mean ones) are welcome.
The game and rating logos were made by Dodochacalo!
---
Thanks to the people that helped us test levels over the years - I hope I won't forget anyone: Akseli, Mobius, Uberwolfie and David
---
[work in progress] Here is a few details about the levels (we each commented on our own levels):
Spoiler
01/ Haute Voltige
This is french, meaning "acrobatic act". At first this level required a trick involving a floater turning around mid-air with a hanging blocker and a well-timed bomber. But as I originally made this level for Lemmini, at some point I decided this was too tedious to pull off and completely changed the solution. Now it's an easy level. Easy levels are nice too.
02/ VDNKh
The title is a reference to the video game / book Metro 2033. VDNKh is a Russian metro station where some of the plot takes place. At the center of the map you can see a defense post with a flamethrower and a barricade. Further on the right a breach goes deep into the unknown, from which creatures may come out.
03/ What the Frick Frack Patty Wack?
This one was just to showcase this odd (but fun) basher on steel behaviour.
04/ Sandstones May Break My Bones
Easiest level of the pack that only exists for its sequel... (see: Incipio 15 below)
05/ Formal Semantics of Modal Logics
This is a simple inversion. The over-the-top layout and title are just to make it look more convoluted than it is.
06/ Quid Pro Quo
Just tried to make a lovely little puzzle here. Sometimes I find it harder to make good easy puzzles and I'm happy when I manage to stay focused on a simple idea without overcomplicating it.
07/ Smells Like Team Spirit
This is your typical basher level! I really love those, and I tried to make this one interesting and fun to figure out. I think the reference in the title is obvious?
08/ As not easy as it doesn't look
This level is broken and needs serious maintenance. It may disappear in a later version of the pack.
09/ Brace Yourself, Fall is Coming
First made for Lemmini, with a self-made rightward entrance. Its title is a reference to Game of Thrones' famous motto ("Brace Yourself, Winter is Coming").
10/ RELEASE THE KRAKEN
This is purely a layout oriented level. I just wanted to make a giant octopus for some reason.
11/ Bridges in the Sky
The title is a song by Dream Theater. I tried to build a layout inspired by this but I'm not really satisfied with the result.
12/ Mountains
Here is a heavy reference to one specific scene from the movie Interstellar. I'm not a fan of this movie but that scene stuck with me ever since and I thought it would be interesting to try and depict it in NeoLemmix.
13/ Something Wicked This Way Comes
Reference to the novel by Ray Bradbury.
14/ Architects of Fortune
Using the chain terrain piece to its full potential! The title is a reference to this song by Circus Maximus.
15/ Been There, Done That
First sequel, where bashers are now miners! An easy level though. (see: Incipio 04 above)
16/ Novelty Act
Another try to extend the basher capacity. This level is clearly gimmicky. Also I got the title here.
17/ Paucity
Just a little puzzle with a few skills. This is the very first level I created for this project!
18/ Ethereal Refinery
No idea how I came up with this title. I guess the lemmings flowing down made me think of droplets running down a still?
19/ Convoi Prioritaire
This is french, I guess you could translate it is "priority convoy". The idea being that the crowd must not be stopped nor turned around. Make way for the Lemming train!
20/ Graph Theory
Initially assigned to a "bonus" rating, this level isn't just about lucky die and retry if you know how... The design here is quite simple yet resembles a pre-Columbian temple. Its title is a reference to the mathematical theory of interconnected objects.
This is french, meaning "acrobatic act". At first this level required a trick involving a floater turning around mid-air with a hanging blocker and a well-timed bomber. But as I originally made this level for Lemmini, at some point I decided this was too tedious to pull off and completely changed the solution. Now it's an easy level. Easy levels are nice too.
02/ VDNKh
The title is a reference to the video game / book Metro 2033. VDNKh is a Russian metro station where some of the plot takes place. At the center of the map you can see a defense post with a flamethrower and a barricade. Further on the right a breach goes deep into the unknown, from which creatures may come out.
03/ What the Frick Frack Patty Wack?
This one was just to showcase this odd (but fun) basher on steel behaviour.
04/ Sandstones May Break My Bones
Easiest level of the pack that only exists for its sequel... (see: Incipio 15 below)
05/ Formal Semantics of Modal Logics
This is a simple inversion. The over-the-top layout and title are just to make it look more convoluted than it is.
06/ Quid Pro Quo
Just tried to make a lovely little puzzle here. Sometimes I find it harder to make good easy puzzles and I'm happy when I manage to stay focused on a simple idea without overcomplicating it.
07/ Smells Like Team Spirit
This is your typical basher level! I really love those, and I tried to make this one interesting and fun to figure out. I think the reference in the title is obvious?
08/ As not easy as it doesn't look
This level is broken and needs serious maintenance. It may disappear in a later version of the pack.
09/ Brace Yourself, Fall is Coming
First made for Lemmini, with a self-made rightward entrance. Its title is a reference to Game of Thrones' famous motto ("Brace Yourself, Winter is Coming").
10/ RELEASE THE KRAKEN
This is purely a layout oriented level. I just wanted to make a giant octopus for some reason.
11/ Bridges in the Sky
The title is a song by Dream Theater. I tried to build a layout inspired by this but I'm not really satisfied with the result.
12/ Mountains
Here is a heavy reference to one specific scene from the movie Interstellar. I'm not a fan of this movie but that scene stuck with me ever since and I thought it would be interesting to try and depict it in NeoLemmix.
13/ Something Wicked This Way Comes
Reference to the novel by Ray Bradbury.
14/ Architects of Fortune
Using the chain terrain piece to its full potential! The title is a reference to this song by Circus Maximus.
15/ Been There, Done That
First sequel, where bashers are now miners! An easy level though. (see: Incipio 04 above)
16/ Novelty Act
Another try to extend the basher capacity. This level is clearly gimmicky. Also I got the title here.
17/ Paucity
Just a little puzzle with a few skills. This is the very first level I created for this project!
18/ Ethereal Refinery
No idea how I came up with this title. I guess the lemmings flowing down made me think of droplets running down a still?
19/ Convoi Prioritaire
This is french, I guess you could translate it is "priority convoy". The idea being that the crowd must not be stopped nor turned around. Make way for the Lemming train!
20/ Graph Theory
Initially assigned to a "bonus" rating, this level isn't just about lucky die and retry if you know how... The design here is quite simple yet resembles a pre-Columbian temple. Its title is a reference to the mathematical theory of interconnected objects.
Spoiler
01/ A Good Lem is a Dead One
My very first Fiat Lem! level, harder to complete on Lemmini (due to bomb timing).
03/ The Wall
Minimalist design on purpose. Its minimalist title is a reference to Game of Thrones' giant ice wall.
05/ Fire & Blood
Part one of a diptych whose gimmick is to have two entirely identical levels (including skills) with just one little difference: entrance and exit were switched! (see: Proficio 15 below)
08/ Snowpiercer
A well-known technique that requires meticulous preparation here. Snowpiercer is a French comic world famous for its cinematographic adaptation.
10/ Ancient Astronauts
Having only one builder forces you to use your miners and diggers wisely. One of my favorite designs, due to its simplicity; the structures made of bricks and stairs somewhat resemble the idea I have of an alien spaceship, hence the title.
12/ Paved With Good Intentions
I always loved puzzles with only a few builders, the poor creatures having no choice but to wander through the level. I guess blockers can be more than just single-use. As the proverb says, what is "paved with good intentions" is the road to... hell.
14/ Latecomers
If it had not been for the low release rate, that level would have been of little interest, except for its design that mimics 3D graphics.
15/ Blood & Fire
Part two of a diptych whose gimmick is to have two entirely identical levels (including skills) with just one little difference: entrance and exit were switched! That second puzzle is supposed to be slightly harder to complete, not enough for the Scando rating though (see: Proficio 05 above)
17/ Bad Reflections
Punny title (a lot of my levels include symmetrical layout though... and punny titles); made easy by its limited room for maneuver... and the conversion to NeoLemmix. The gallows isn't really a problem here, is it?
20/ Eclectic Power
Two nearly identical halves that must be solved differently (hence the punny title). Maybe a little too difficult for the Proficio rating.
My very first Fiat Lem! level, harder to complete on Lemmini (due to bomb timing).
03/ The Wall
Minimalist design on purpose. Its minimalist title is a reference to Game of Thrones' giant ice wall.
05/ Fire & Blood
Part one of a diptych whose gimmick is to have two entirely identical levels (including skills) with just one little difference: entrance and exit were switched! (see: Proficio 15 below)
08/ Snowpiercer
A well-known technique that requires meticulous preparation here. Snowpiercer is a French comic world famous for its cinematographic adaptation.
10/ Ancient Astronauts
Having only one builder forces you to use your miners and diggers wisely. One of my favorite designs, due to its simplicity; the structures made of bricks and stairs somewhat resemble the idea I have of an alien spaceship, hence the title.
12/ Paved With Good Intentions
I always loved puzzles with only a few builders, the poor creatures having no choice but to wander through the level. I guess blockers can be more than just single-use. As the proverb says, what is "paved with good intentions" is the road to... hell.
14/ Latecomers
If it had not been for the low release rate, that level would have been of little interest, except for its design that mimics 3D graphics.
15/ Blood & Fire
Part two of a diptych whose gimmick is to have two entirely identical levels (including skills) with just one little difference: entrance and exit were switched! That second puzzle is supposed to be slightly harder to complete, not enough for the Scando rating though (see: Proficio 05 above)
17/ Bad Reflections
Punny title (a lot of my levels include symmetrical layout though... and punny titles); made easy by its limited room for maneuver... and the conversion to NeoLemmix. The gallows isn't really a problem here, is it?
20/ Eclectic Power
Two nearly identical halves that must be solved differently (hence the punny title). Maybe a little too difficult for the Proficio rating.
