So there were half a dozen or so levels in the end that required new solutions, including 'The Aquatic Ruins', of course. I'm also including my previous solution for 'Deep Chasm of Coinage'; it didn't actually need a redo though, so guessing it wasn't a backroute in the first place.

Spoiler

The only thing that makes me think 'The Aquatic Ruins' could be another backroute is the fact I didn't need the walker pickup, although that I suspect that might be a red herring Main difference to my last solution is that I couldn't afford to waste a jumper interrupting the laserer this time around.

You'll have to let me know if I've found any more backroutes!

Thanks, @Mobiethian and @kaywhyn for this update! I've already started looking at some of the updated levels and a fair few of my previous replays no longer work, so I guess I must have backrouted them before - more or less egregiously XD This is a good thing though, as I've now got more NL to play!

Thanks for the replies all! I'm so sorry that I'm only just getting to respond to them now It's been an honor working with Mobiethian here to pre-test the entire pack before release and also to help him with the v2.0 update!

I've added a short note next to the custom sounds download to let players know to backup the sound folder if one chooses to use them, as they will overwrite the defaults! That is indeed great advice @Icho gave there for Mobiethian and as a heads-up for everyone else

Now my response to the levels where Mobiethian credited me for my solution:

Deep Chasm of Coinage

Both Dexter's and Guigui's solutions I consider acceptable. Guigui's is identical to my solution in nearly every way, but Dexter's eventually uses my solution element at the start, just in a different order from ours. In any case, well done to the both of you for your great solves for the level!

The Aquatic Ruins

Nice, JawaJuice, Guigui, and Dexter have all more or less found the same backroute Still, great job with solving this level with impressive solutions! Mobiethian and I have made some changes which will hopefully enforce the solution I helped him come up with better I'm not sure if the level will hold up better now with them, but let's see!   

There was a slight boo-boo in "The Steel City". That has been changed and updated in the link.

I'm gonna be frank, I hate the my interest and inspiration in Lemmings has been at an all time low. I've haven't touched NeoLemmix in weeks, I haven't made a concept for any project since I made one part of a level idea. And my mind has been very empty in terms of level design ideas.

I've been prioritizing videos as of late simply because I've lost my motivation to make levels simply because I lost my flame after once having it. My Burnout project fizzled out rather quickly. And Millas and QSML has been at a stand still because of it. I've had such a bad month and April hasn't been going better. I'm not in the head space to create and I just feel like I just only merely exist, nothing more or less. I just want finish something that should've been finished years ago and now im back to were I was back in 2023. A lot of an existing projects, with no ideas, motivation or steam to keep it going.

I'm sorry for dragging my feet but if I was Sisyphus in this situation, the bolder would've crushed me at this rate.

Howdy folks! Guess what? We now have a 2.0 release to bring to you! This version has backroute fixes and additional graphics added to most of the levels.

Download here: https://drive.google.com/file/d/1I_lmWZM_VZyi_GvzU9IEJ23canSgyJWh/view?usp=sharing

The download link has been replaced at the start of the topic as well. Have fun! Thanks for playing!

Note: If more backroutes are found, feel free to send me a PM and I'll see what can be done.

Congratulations on the 3.1 Update!!!
Personally I think it's a work of art!

Will fully utilize it in the following days.
But even at a first glance it looks so powerful.

I immediately tried the pieces list and it works like a charm with a level consisting of 200+ pieces. It is SO useful especially with non-repeated, uniquely named custom pieces, it is such a dream!

You cared, you listened and you gifted. I can only hope that you are enjoying as well, the fruits of your love as much as I do.
Sorry for my belated response, had been away from my home and my pc for the past few days and I JUST noticed your release, looking at the github commits.

May life put a smile on your face. Have a wonderful day!

And, this should now be fully fixed. We can now prioritise objects by type rather than individually.

So, all OWWs have equal priority, and lower priority than all traps, which have lower priority than all force fields/blockers, which have lower priority than exits. This is the list in full:

    static final int PRIORITY_GADGET_MASK =
        Stencil.MSK_EXIT
          | Stencil.MSK_BLOCKER
          | Stencil.MSK_TURN
          | Stencil.MSK_TRAP_FIRE
          | Stencil.MSK_TRAP_REMOVE
          | Stencil.MSK_TRAP_LIQUID
          | Stencil.MSK_ONE_WAY;

This additional layer of abstraction is the key; we now have fully working object prioritisation in RetroLemmini.

And, OWWs can be overlapped exactly as before (i.e. in previous versions of Lemmini)!

Fixed in RLPlayer commit 1285213.

OK, I'm a step closer to having this fixed.

It turns out that OWWs (and indeed any objects) were never truly 'overlapping', at least not in the sense that their triggers were all effective at the same time. Lemmini has always had index-based prioritisation for objects. So, whichever object was drawn last occupies any given trigger pixel.

For instance, in previous versions of Lemmini, laying a OWW over a fire object will override the fire object.

I wanted to fix this in RetroLemmini by hard-coding the object prioritisation, with Exits being at the highest priority. This was all well and good apart from the fact that each individual OWW object had to be prioritised separately, which is why any levels using overlapping OWWs were suddenly broken: RetroLemmini was pre-selecting which OWW object should be at the highest priorty, regardless of draw order (which is what the levels relied upon previously).

I've implemented a fix in which Exits are now the only object which is prioritised over all others (RLPlayer commit d8ae78d). All other objects are once again prioritised by draw order. However, I'd like to see if I can refine this further. It seems silly that a OWW overlapping a fire or water object should effectively nullify the fire or water.

Further work is needed.

OK... frustratingly, the revert didn't actually fix the issue. I've now reverted the revert!

So, we can overlap OWWs again, but there is some wierd stuff happening when they overlap. I'll come back to this later.