There are various reasons, that the green checks on cleared levels/packs may disappear , as far as I know.

One of these is if you change your username on the Neolemmix settings. Another may be  ( if I'm correct ) if you use the "clear records" option, on the level select menu . There is also a dedicated file on the settings folder (userdata.nxsv) , where the catalogue of the levels you have completed and other stuff like max savings are stored. If that file will get deleted, these green checks will most probably disappear.

Fortunately it is very easy to restore these green checks. You need to run a mass replay check on the levels and packs you have completed and they will be restored.

Orange check on a level means that you have a newer version of the level now , compared to the version you had when you completed the level. That may be due to a large change like a backroute fix , or even due to small changes , like a small visual change for example.
If these changes don't affect your solution, then running your replay or doing a mass replay check will make it become green again.

I have uploaded the version 1.16 of the pack. It contains the version 1.01 of Pollux 6 - "Floating Above the Valley of the Clouds" .

The new version has terrain which is more cpm-accurate , plus some other changes on the terrain. You will need to download again the 'turrican special" tileset for this version of the level , so I have attached the link for my dropbox in the first post , so you can download from it ,the latest version of the tileset.

Also the save requirement for the level has been increased to 140 lemmings , and the skillset has also been changed , so I have uploaded in the first post , the updated replay collection , which also contains the replay of the solution of the new version of the level.

Here is how the level looks with the new changes :

I have uploaded the version 1.01 of "Floating Above the Valley of the Clouds" .

The new version has terrain which is more cpm-accurate , plus some other changes on the terrain. You will need to download again the 'turrican special" tileset for this version of the level , so I have attached the link for my dropbox in the post which contains the level, so you can download from it ,the latest version of the tileset.

Also the save requirement for the level has been increased to 140 lemmings , and the skillset has also been changed , so I have uploaded in the post which contains the level , the updated replay of the solution of the new version of the level.

Here is how the level looks with the new changes :

I have updated the 'Turrican special" tileset , which is needed for the pack , and I have added the link for my dropbox , which contains , the updated version of the tileset , in the first post .

The updated version contains reworked versions of the backgrounds of the levels : "The House With the Thin Foundations" , "The Astral Monolith" , and "In the Sight of the Colossus" .

The new backrounds are the same visually , but now they are 100% "clear physics mode" - accurate . The gameplay and solutions of the levels have not been affected .

Also the update , contains the assets , that are needed , for the level "First Light in a Parallel Dimension" , which I plan to add it , on the next update of the pack .

I have updated the 'Turrican special" tileset , which is needed for the pack , and I have added the link for my dropbox , which contains , the updated version of the tileset , in the first post .

The updated version contains reworked versions of the backgrounds of the levels : "The House With the Thin Foundations" , "The Astral Monolith" , and "In the Sight of the Colossus" .

The new backrounds are the same visually , but now they are 100% "clear physics mode" - accurate . The gameplay and solutions of the levels have not been affected .

I have updated the 'Turrican special" tileset , which is needed for several of my levels , that I have posted them in this thread , and I have added the link for my dropbox , which contains , the updated version of the tileset , in the post which contain the levels , that the tileset , in order to work .

The updated version contains reworked versions of the backgrounds of the levels : "The House With the Thin Foundations" , "The Astral Monolith" , and "In the Sight of the Colossus" .

The new backrounds are the same visually , but now they are 100% "clear physics mode" - accurate . The gameplay and solutions of the levels have not been affected .

Here is my first pack for Lemmix , called "Mikes Lemmix Pack" . It contains 10 levels , which is practically all levels , that I've created for Lemmix until now .

Six of these levels require the use of various glithes in order to be solved .

Two of them are based on challenge solutions by Richard Diaz and Alfonz1986 .

All levels have been tested on "Custom Lemmings" physics mode , except for "The Awesome level returns!" , which has been tested on "dos original lemmings" physics mode .

About the music : I haven't upladed the music pack for the levelpack yet , but very soon , I'll try to create two music packs for EricLang's nmew Lemmix player , and for Golems , and I will post the links for them , in this thread .

About Custlemmix : There are three levels , that if you will play them on Custlemmix , will have some objects being misplaced . That happens because Custlemmix has a restriction , in which it requires the x coordinate of the position of each object of the level , to be a multiple of 8 , or else the object will appear misplaced on the level. Fortunately the affected items are decorative , so the gameplay is not being affected , but the look of the level is affected. The affected levels are "The Crystal Coves" ,  "Now you're stuck ( part 2 )" , and "The squares fight back (part 2)" .

Here is how some of the levels look :




                                          "The Crystalline Fortress"



                                    "Now you're stuck ( part 2 )"



                                                         "Spaces within spaces"                                                                                       



                                                           
                                                                                              "Science from the 4th dimension"

This is the Lemmix version of my level "The Awesome level returns!".

This level is a "CSTame-like" challenge version of Taxing15 (What an AWESOME level) , based on a challenge solution by Richard Diaz .

I have also attached the replay of the solution. The level has been tested on Custlemmix , on "Dos original lemmings" physics mode .

Link for the music track for the level: https://modarchive.org/index.php?request=view_by_moduleid&query=121408

I have uploaded , the version 1. 15 of the pack. It contains a new level. That level is : Arcturus 2 - "First Light in a Parallel Dimension" . This level contains AI art .

In order to play it , you will need the updated version of the "turrican special" tileset . I have attached it in the first post.

The new level has been replaced the "The Complex" , which was previously Arcturus 2 . That level , has now been moved on the first rank , and it is now , Sun 9 .

I have upladed also , the updated replay collection, which also, contains , the replay of the solution , of the new level.

Also I have uploaded , the updated version of the soundtrack of the pack , in my dropbox , and I have posted , in the first post post , the link for my dropbox , which contains , the updated soundtrack , of my pack.

Here is how the new level looks :

Here is my new level. It's called "First Light in a Parallel Dimension" . This level contains AI art .

In order to play it , you will need an updated version of the "turrican special" tileset . Here is the link for the tileset :
https://www.dropbox.com/scl/fi/3ae95skkiongijv8771iw/turrican_special.zip?rlkey=1a6wcrnoa36cunwzw8zdrpubp&st=jvz4hvzs&dl=1

I have also attached the replay of the solution.

Link for the music track , for the level : https://modarchive.org/index.php?request=view_by_moduleid&query=142203

For the music track , create a folder , called "Turrican projects" in your music folder , and put the music track  inside that folder.


Here is how the level looks :

Here is my new level , called "Science from the 4th dimension" .

It uses an art style , that Pieuw and Armani , have used for their levels.

The level requires the use of some glitches , in order to be solved.

I have also attached the replay of the solution. It is viewable on  "custom lemmings" viewing style.

Link for the music track for the level : https://modarchive.org/index.php?request=view_by_moduleid&query=104370

About the replay : The replay has been created on the playtest mode of the original Lemmix editor , on "custom lemmings" physics mode. I've tested it also on EricLang's new Lemmix player , but it doesn't work on that , due to differences on the order , that the lemmings appear on the level.

So , my "to do" list for this levels , contains creating a solution replay for EricLang's new Lemmix player , and also testing it on Custlemmix and Golems.

EDIT : The level that I had initially uploaded had a typo on it's name , so I re-uploaded it with the correct name . Also , I added a replay of the solution , for EricLang's New Lemmix Player . The replay has "new lemmix" on it's name .

Here is how the level looks :

I have uploaded, the version 1.14 of the pack , which contains some big changes.

First of all the Rigel rank , has been split into two ranks now. These ranks are Arcturus and Rigel. And 5 levels that previously were in the Rigel rank , are in Arcturus rank now.

Also the "AI art" levels , and the ""Excavations in the Cubic Cave" level , that previously were in the Bonus rank , are now in the main ranks.
 More precisely "Excavations in the Cubic Cave" is Sun 3 now.
                "The Mushroom Village" is Sun 5.
                "In the Sight of the Colossus" is Pollux 3.
                "Floating Above the Valley of the Clouds" is Pollux 6.
                "The House With the Thin Foundations" is Arcturus 3
                 "The Astral Monolith" is Arcturus 8

Also , the new version contains a new level. That level is : Arcturus 7 - "A.T. in construction" . It is based on a challenge solution for Genesis - Sunsoft 29 ( "I am A.T." ) .

I have upladed also , the updated replay collection, which also, contains , the replay of the solution , of the new level.

Also I uploaded , the updated version of the soundtrack of the pack , in my dropbox , and I have posted , in the first post , the link for my dropbox , which contains , the updated soundtrack , of my pack.

Here is how the new level looks :

Here is my new level. It's called "A.T. in construction" . It is based on a challenge solution for Genesis - Sunsoft 29 ( "I am A.T." ) .


I have also attached the replay of the solution.

Link for the music track , for the level : https://modarchive.org/index.php?request=view_by_moduleid&query=47747

For the music track , create a folder , called "Turrican projects" in your music folder , and put the music track  inside that folder.

Here is how the level looks :

 I have uploaded, the version 1.19 of the pack. It contains the Superlemmix version of my new level. That level is : Bonus 6 - "Floating Above the Valley of the Clouds" . That level contains AI art .

In order to play it , you will need the updated version of the "turrican special" tileset . I have attached it in the first post.

Compared to the Neolemmix version , the Superlemmix version , has a different solution , and also contains Freezers , Laderrers and Ballooners.

I have upladed also , the updated replay collection, which also, contains , the replay of the solution , of the new level.

Also I uploaded , the updated version of the soundtrack of the pack , in my dropbox , and I have posted , in the first post , the link for my dropbox , which contains , the updated soundtrack , of my pack.

Here is how the level looks :

I have uploaded, the version 1.13 of the pack. It contains a new level. That level is : Bonus 6 - "Floating Above the Valley of the Clouds" . That level contains AI art .

In order to play it , you will need the updated version of the "turrican special" tileset . I have attached it in the first post.

I have upladed also , the updated replay collection, which also, contains , the replay of the solution , of the new level.

Also I uploaded , the updated version of the soundtrack of the pack , in my dropbox , and I have posted , in the first post , the link for my dropbox , which contains , the updated soundtrack , of my pack.

Here is how the new level looks :