Disclaimer: Despite my best efforts I have not managed to solve the puzzle properly, but more about this later.

Instead I repeated what I did last time - analyzed the code, found out sequences that satisfy the codelock (i.e. passwords that work same as 'one true' password) and picked the easiest one to read and remember.

So, before you can enter the code, you need to find the secret room with portal.
At the spawn, turn around and walk outside.


Continue going forward, there should be underwater tunnel at right hand side.


Follow the tunnel to the room. In order to get inside the secret you will need to pass through illusory wall (marked black on screenshot). It is easier to do that while crouched.


So this is secret room.


You're interested in wire control unit on left wall.


Create a value chip with string value of
.

Now wire !? input from wire control unit to the value.


Voila!


You can now access a secret!


Enjoy!

Also this code will work for day version of map, so you can use it instead of my old code, that was, apparently, circulating around in the community, to the point that demazure had seen fit to actually change the system so that code doesn't work anymore. Hence me finding out and showing up for a round two, heh heh.

In case you're doing this on multiplayer server and it doesn't work - chances are, somebody already tried to access it and failed. To fix that, create a second value chip with empty string (i.e. string value that has no text in it), wire the control unit to it, and then wire control unit back to the code value.

I'll say it straight - while the puzzle is clever, it is admittedly very bad. Worse than a lot of moon-logic puzzles from classical point-and-click adventure games.

For anyone still interested, I gathered a lot of particular info but it doesn't want to fall in complete picture.

The starting point is obvious: coordinates. With sv_cheats 1 and setpos we will quickly arrive at these steps.


At the day version, those were just differently-colored steps, which immediately rang the 'bit representation of a number' bell in my CS-singed brain.
In CS, you're supposed to read those from right to left, rightmost corresponds to two power zero, i.e. one, next one corresponds to two power one, i.e. two, next to two power three, i.e. 4, et cetera. You sum the powers of two corresponding to elements that have "on" state (i.e. 1 bits, as opposed to 0 bits), and you get a decimal value.

That's exactly what the "3 2 1 0" part of the matrix on the (day version) hint alluded to. Powers of two for translating binary to decimal.

Now this is where problems begin. Classically, it is sort of agreed between computer scientists that byte is eight bits. The single step has 6 tiles. Ok.
There are always 2 "empty steps" between bit steps. That may or may not be actual data just consisting of zeroes that we need to also factor in. Or it could be just demazure making things look nice. You can already see that puzzle has too many uncertain variables that you cannot check for sure, and have to factor in for calculation of final result.

But this is not the end of it, there's also this thing called endinan-ness, which says how the number is actually stored in computer's memory. It is usually relevant when we're dealing with multibyte numbers. Let's assume demazure was nice (or simply didn't know about that!) and that we have to read it in straightforward manner.


So, the main question, what do we do with these five numbers? Apparently you're supposed to plug them in slots on the main hint, but the problem is, all of these numbers except 8 take 2 slots, in both hex and decimal bases.

Moreover, the same '4x4 matrix' that hints to binary representation has also letters, which results in questiXPLOSION: Do these allude to position of bits on the steps? Where is A and B? What does horizonal position mean? Does it mean we shift E left one bit? What is E, anyway? Why does it denote only 3 letters? Do we play this as sudoku?

I'm not even starting on whatever the hell these lighter tiles are now on night version. They are sub-tiles which sometimes have a black tile and sometimes don't, and I have absolutely no clue where that plays in the rest of the puzzle.

The A106B34 sequence also should apparently be in hexadimal (the little numbers beside the brackets denote the base of number), according to day map hint and demazure's comment.

To add insult to injury, when demazure came down to us, mortals, and dropped a single hint, it was explained exactly that steps = binary. I feel that's not the thing in most dire need of a clarification. Important step but not really.

At the time we can assume that A = 35, B = 40, C = 8, D = 49, E = 48.

Now let's address the elephant in the room. What in seven hells IS minus j hat (with LOOK on it)?
Ok, I have found the J room (note coordinates on screenshot).


I also noticed that room is 5 tiles wide and exactly 8 tiles long, which makes the J parts ideal candidates to be read as bits. Assuming we want to read it as binary, and that obvious direction would be from the entrance.
But having 3 numbers made no sense, we're not required 3 numbers, if anything, we'd be required 5.
Let's assumbe that the hat (^ thing over j) is actually a direction kinda like one next to matrix.
Then we have

So it would be logical to assume that - J means we have to subtract the components of J from elements from stairs, right?


So we make another logical jump and assume the letter slots in numbers can hold more than one digit, so we stick these in template, and get hexadimal number 0x161062634, turn it into base 31 and get... 6kr7c02.
Well that doesn't look like 'series of words' demazure was referring to.
I also checked it in decimal system, and switched A and B around for both hex and dec. Result is still garbage.
So it either means that I'm missing something about it, or J is something else entirely, like a number in base 31. Could be hat having some obscure mathematical meaning, like exception to set or something.

I'm not even mentioning the damn minesweeper board and my thoughts on how possibly the subtiles on the ladder can tie into this. Comparing this with day version I'm leaning towards assumption that it's a decoy or alternative solution path, as the numbers at the start of puzzle were left the same. So if you had all you needed to solve puzzle in day version, night version doesn't really need those either, since password is same.

So I'd be obliged, if anyone was nice enough to shed some light on this puzzle. Oh and especially, what the hell does this thing do?


So the main problem with the puzzle is lack of context, and combinatorial explosion when you try to interpret the hint. There are no middle-way points where you can somewhat confirm that you're going in proper direction, and that makes the task of exploring all the possible variants even more difficult.
It is also tied to very specific knowledge to be able to solve it. I feel like having more knowledge actively obstructs the path to solution with unnecessary forks leading nowhere.

Oh and the secret room has decal with words on it but I cannot make out what they are even on the alphachannel of the texture. I'm fairly sure it's hall of fame or betatesters list or something.

Preliminary info: key_5 is a physbox brush entity found in a secret room in the map.
It has no obvious use, however author declared it to have certain undisclosed use in this map, as opposed to previous excess map installments.

This was further expanded with night update of the map, where changelog contained following note:
"Added additional key5-block functionality"

Note the word usage: "functionality".
Not "application", not "usage", "functionality". This would imply that some changes were made to the actual block, expanding some already-existing function set.

However, there's still no obvious use for it, so when I was reiterating night's puzzle I decided to analyze it for all it's worth, including points I have already checked for day version of the map.

First off, this is how it looks inside bsp (entity lump):
As we can see, no outputs, no obvious hints as of how to use it.


Note: In gm_aquablocks! The block is called key_4 (both old and new versions)
in gm_excess_construct_13 it is called key_3 and has different structure which doesn't align to the 4x5 grid.
in gm_excess_waters it is called key_3 and has same form as 4 and 5
in original gm_excess_construct it is called key_3 and has the same form

If we write down partial timeline we get this:

gm_excess_construct (original) - key_3
gm_excess_waters - key_3
gm_aquablocks! (original) - key_4
(all others including this map) - key_5

So the numerical designation of the keys progresses with timeline roughly, but it isn't strictly tied to map's number in series or year the map was made.
This doesn't really display any practical applicability, though.


So with all that preliminary stuff outta way let's get to the core of over-analyzing endeavor, shall we?
Here is a congested list of things I was checking the key_5 and the map against:
- [NO] - Direct mentioning in lua (classing targetname lookup)
- [NO] - Indirect lookup via lua (lookup by classname, brush model(*79), hammerid, coords, specific keyvalues, mass)
- [NO] - Direct mentioning in bsp
- [NO] - Indirect mentioning in bsp - Wildcard lookup
- [NO] - Indirect mentioning in bsp - classname lookup
- [NO] - Check flags
Spawnflags 524288 = single flag, 2^19 - Generate output on +USE, but there are NO outputs bound to this, no mentions of OnPlayerUse in bsp either
- [NO] - Hidden actuators in bsp
- [NO] - Filter ents of any sort
- [NO] - Triggers that can interact with it via physics objects flags - Only teleports
- [NO] - Anything special about room with it? Coords?
- [NO] - Physics objects that can react to it
studiocamera? It has it's motion disabled and nothing appears to enable it back. That's another mystery hanging.
Or another case of having to use physgun_limited 0...
- [NO] - Something related to buyonancy or other emergent physical effect? - It sinks like a brick, who would've thunk!
- [??] - Visual importance
- [NO] - The dimensions
Dimensions are 5x4x3 of 4x4 cubes, i.e. 20x16x12
The center has been moved one unit to the positive infinity on Y axis
- [NO] - Using it as proxy to access hidden brushes with wire inputs - Doesn't work, obviously
(talking about that SNEAKY wiremain_b11e brush in the corner! Nonsolid too, can't wire up to it.)
- [NO] - Check lightmapscale/lightmaps directly - could be hidden writing baked in key's lightmaps
- [NO] - Check for texture shenanigans
Texture offsets are too big to be ASCII, and sometimes they're negative
Texture is standard stone/stonewall050a texture with scale of 0.1 on both X and Y
- [??] - Visual easter egg - it can be positioned in such a way that it completes a picture - see visual importance
- [NO] - Slice the thing, see if it makes letters
It does not (best case scenario it's something like MAIAM), however, 5 3x4 slices look like Ancient Alphabet from stargate, but it isn't it.
- [NO] - Can the brush be interpreted as binary or smth?
- [NO] - Overlaid sections importance - Volumetric boolean operations, maybe xor'd?
Does not appear to be any sort of informative pattern
- [NO] - Does it make sense to fill the 'missing' slots in it with something? Props?
- [NO] - Using it to prop up and completely block rotating doors
Ridiculousness aside, technically this was possible on map gm_excess_construct_13, as there's exactly one prop_door_rotating in the map, and key stone can be taken out of the secret,
and that contradicts the brand-new usage the island map was supposed to bring us. Besides - certain props can do that better and they have added benefit of having you as owner,
so other players cannot pull it out with their physgun.
- [??] - Interaction with external tools(akin to protector brush for vmex)?

Not all of these could be checked fully and reliably, those which weren't are marked with "[??]".

So, having eliminated all aforementioned options I can only suggest some really esoteric uses for it.
1. There is high probability that this is unsolvable mystery that is there just to create... well, sense of mystery. Just to mess with player. Psychologically speaking, it will not allow player to mentally mark map as 'complete', even if one has found all other secrets, thus making the map somewhat memorable. This usage would explain the overall vagueness and alluding to some functionality, that's needed just to keep the interest around and curb the impression of a running gag / useless knick-knack the key block has gained from previous maps.
2. Second most probable option is that the block has purely symbolic meaning, linking the maps thematically and serving as proverbial keystone that every map ought to have in it's core. This line of explanation gets real esoteric real quick, you first start with idea that it could be that key symbolizes interlocking approach to architecture widely used in excess series, and you end up discussing the key as simulacrum object that is a spatial projection of abstraction of space through deliberately incomprehensible symbolism. This, however, contradicts the 'functionality' statement from demazure. Symbolism ain't functional, but it's entirely possible that it's not US who get to use that 'functionality'.
3. The rest are really far-fetched options: mainly incredibly obscure usage, like abusing the fact that it has no owner, thus tricking certain addons into not working, or using it as a measure tape of sorts, as it allows measuring 8, 12, 16, 20 units.
4. Lastly, it could be that functionality is really obvious and mundane but it absolutely escapes me, and by extension bunch of other people, who are equally puzzled by it. But in that case someone probably would have pointed it out already.

TL;DR: It probably doesn't have any practical use. Technically speaking neither does the secret room, but at least the room is a nice-looking, hard-to-reach getaway place.