Hello, dear players!
The new update 0.598 is now LIVE on Steam for Pre-Alpha testers! It includes over 100 reported bug fixes, many gameplay and Quality of Life improvements, and a full Lighting & Static Reflections rework!
Once it has been tested for major issues in Chapter 1 New Game, we will update the Steam Demo.
If there are only minor bugs, or major bugs exclusive to New Game+, or later Chapters than Chapter 1, a hotfix update will be made in 1 or 2 weeks, but the Demo will still be updated before that (if these issues do not impact Chapter 1 New Game).
In this post, we'll talk about the major changes that were done for this 0.598 update!
The reason why players awaiting for Steam keys have still not yet received them, is because we have run out of Steam keys and have reached the authorized limit. We will be migrating the game to the Steam Playtest system to override this limit. This will likely change the way you access the Pre-Alpha, even for existing Pre-Alpha testers. We will keep you updated on when and how this migration will take place.
Once this update is stabilized for the first major bugs in Chapter 1 New Game, and the Demo is safely updated on Steam to 0.598, we will take some time to work on a maintenance update for the Pocket Edition. It will include many bug fixes and some first visual improvements. We'll keep you posted on that, but you can expect a BETA very soon!
First, we'll highlight below the most important new elements from this update.
One of the major changes for this update, that took a long time to implement, is a full rework of the lighting system.
The impact may not be noticeable to all players, but the decision to rework this came from the following reasons:
As a result, in general, the following changes can be noticed:
Below are a few screenshots to illustrate these differences mentioned above
Door / Vent Frames | OLD:

0.597: Door and Vent frames were often very white when lit by any lights, especially the flashlight
Door / Vent Frames | NEW:

0.598: Door frame is now still metallic, but is no longer purely white even with flashlight. Bloom is less intense.
Cube Borders | OLD:

0.597: Cube borders / edges were reflecting extremely bright white light
Cube Borders | NEW:

0.598: Cube borders are still highlighted, but more realistically, less exaggeratedly white even with flashlight active
Inside Vents | OLD:

0.597: Vent walls were reflecting a lot of white lighting - could be blinding
Inside Vents | NEW:

0.598: Vent walls are reacting more realistically to reflected light, and less blinding. You can actually see the light source.
In addition to the lighting system rework, here are a few new changes worth noting related to it:
Now that the game is less blinding, and more realistic, we will likely add a few more highlights in the future, but they will remain less intense and not on large surfaces.
Another major improvement which the Lighting Rework allowed to achieve, is to significantly reduce the presence of the white reflection circles, that you may have noticed on the grounds and ceilings.
In reality, these need to be somewhat present, to be accurate and provide a metallic feel to surfaces.
However, before this update, they were extremely strong, very large, and present in every single area of the game, and on every object. This could be too disturbing and a strain on the eyes as well.
From this update, the white reflection circles are now:
Below are a few example comparisons from 0.597 / 0.598 to see the differences with these light circles
OLD:

0.597: Large white reflection circle on the ground
NEW:

0.598: White reflection circle not visible in this area (fully disabled)
OLD:

0.597: Windows reflected light as a concentrated white circle, very strongly
NEW:

0.598: Window reflects light in a more subtle, diffuse manner, and the ground circle is no longer distracting
OLD:

0.597: White reflection circles for 2 lights on the ground in this room, ceiling light reflection is very strong
NEW:

0.598: White reflection circles are not visible anymore, and the ceiling light reflection is less intense
OLD:

0.597: There were 2 strong white reflection circles on the grounds
NEW:

0.598: Here, the 2 reflection circles are intentionally kept, but you can notice they are much less distracting, and have a dirtiness effect instead of a perfect circle, which looks more realistic
You may have noticed that in various Chapters, quite often, Static Reflections could be greatly distorted:

0.597: Example of some inaccurate reflections
This was the result of many optimizations. For this update, all static reflections of all Chapters have been significantly improved, in order to reduce the noticeable inaccuracies, and reduce distortion.
They will now, most of the time, have less visible inaccuracies:

0.598: More subtle, and significantly more accurate reflections on the ground. White reflection circles are also much less distracting (but intentionally still present).
Here's another example of an area with distorted / inaccurate reflections:

0.597: The ground has distorted, inaccurate reflections, and the walls as well
NEW:

0.598: More accurate reflections on the ground, no distortion on the walls
It's important to note that some distortion and inaccuracies are still present, as is the limitation of those static reflections, which are very optimized and can run smoothly even on integrated GPUs.
If you search and analyze, you'll always find inaccuracies / distortions - and that's okay, because they are now considered "good enough" for most areas.
Some areas cannot have good Static Reflections, and cannot be solved - these areas now have less visible Static Reflections, or no static reflections at all.
The only way to have better reflections from this point in these problematic areas, is to use Dynamic Reflections mode.
Please report areas in which even these new Static Reflections are way too distracting, and they will either be improved or made less visible.
Another major visual improvement in 0.598 is the lights' lens flares rework. Many of the existing lights were using a simple "star shape" lens flare effect, which didn't always look good.
All light lens flares have been reworked, then adjusted individually.
These new lens flares now add a visual effect on most lights, of "horizontal line lens flare". The further you are from the light, the more visible the effect is:

They all have been adjusted to avoid being too strong / blinding, but you might still find some that are too intense. Up close, they might still look like “small stars”, which isn’t great, but they still look significantly better than the previous light flares, which were simple circular spherical points.

In addition, it’s now more consistent, as all lights have the same effect (previously, many lights were missing them) - even though it's now more or less visible based on light intensity and light “importance”.

Since the addition and rework of the new Lens Flares - which are now present on all lights - you can now also select adjust how many of them you want:

You can now click on the new Monitor option to change on which monitor the game should be rendered.
Doing so will apply any pending graphics options changes, and instantly change display and update the available resolutions accordingly.
It will always default to maximum resolution after switching. This option is unavailable if you have a single monitor attached:

0.598: New Monitor option
The game will now show less options in resolutions. This is normal, as previously it could list resolutions that your monitor couldn’t handle at the regular refresh rate.