FWIW I’m reading your updates with interest.
I agree that the Tetris area(marsh/swamp) was probably the hardest section. I am so bad at visual/spatial things, it was a huge struggle.
I did find the Town to be tough, too, though we made it through fairly well.
The ending, when you do reach it, really does end the game. Be aware of this, since if you have any unsolved puzzles that you wanted to go back and try, you’ll need to reload from an earlier save to do them.
Also, there are some special challenge puzzles in an extra hidden tunnel area. You don’t need to complete them to finish the game, but they are fun.
A falsehood falsehood articulated while revealing a minor spoiler, followed by a major spoiler. Jesus!
There is no danger, you just reload the last save and everything is there.
mahaloth if you somehow see this message first, do not read any messages prior to it, by any author.
I will likely finish the game, then leave it behind. While not 100% finished, I really feel like 11 lasers plus the mountain(400+ main puzzles) is just about enough for me.
Funny you should use a top-of-mountain image for that: I think each statue represents a different way people can respond to what the game as a whole is trying to represent. 
Believe it or not, I just spent an entire drive home in a mild rage over your post, I was actually composing a pitting over this. But I’ve calmed down. Lemme just explain a bit in the following spoiler-tagged text.
[spoiler]It’s integral to the experience of the ending you’re discussing that the player not know what’s going to happen until the very very end of it. You’ve ruined that because now Mahaloth won’t be wondering about this. He knows from the beginning of the flight that it’s going to be completely over–over over. That was supposed to be a surprise. That was supposed to hit the player. It’s part of the very message of the game.
Plus you’re not even right about the details. All you do is load the last save–it has you inside the cage, you unlock the cage, and just walk out and continue on as though you’d never “ended” the game.
And the special area you referred to–it’s typically called “The Challenge,” and it’s fairly large, equal to more than an island region for example, and rewards you with a final video clip for the under-the-windmill area so it’s, yeah, a pretty major thing. Moreover understanding THAT it exists and HOW to get there is in itself a puzzle, and you’ve spoiled this by mentioning it prematurely. Instead you should fucking (sorry) let the player finish and only if the player has indicated he thinks he’s all the way done, you mention something like “you know… you really only needed seven lasers to get in that mountain. What do you suppose the extra four did?” and give the player the fun of discovery! Come on! How can you not understand this? :([/spoiler]
There I’m done.
And this may be a spoiler even to you, based on what you said:
And you know what, there’s even a third ending and your post misleadingly suggests that once you’ve hit the second ending (The Challenge) you’ve seen it all.
Minor spoiler question:
How many video clips have you found?
- Connections video, Guy with candle, and Guy being interviewed on a stool.
I just solved a series of panels that are my proudest individual gaming accomplishment ever. I came super close to looking up a hint, but pressed through.
Probably not the hardest challenge for some, but it nearly killed me and my wife. She solved 2-3 panels, but the final one was mine. When that cable turned on, I pretty much fist pumped.
I’ll spoiler it. This pic contains the solution, which I am glad to have not seen in advance.
[spoiler]It’s the one where each solution had to fit the entire row of panel puzzles.
Here it is. When that green cable lit up, I celebrated.[/spoiler]
Yeah I had to take a breather when trying to solve that last one in that set. 
I literally grabbed my Ipad and took a screenshot. I’m basically saving it as a life moment, which may be a sad commentary on me.
Hey…did you solve the puzzle in the shipwreck? It’s notorious for being the games hardest puzzle, but I solved it within 10 minutes or so. I’ll spoiler details.
It’s solved using a combination of ship creak sounds and water dripping sounds. I found that I could mainly set aside the sound aspect and focus on symmetrically touching each “dot”. It did line up with the sound, but more conveniently than intentionally.
Here is an image of it. No spoilers, the solution is not on it.
That puzzle hit me on a really bad night (and I mean that in several senses, one of them quite serious) so to be honest though I’m certain I would have solved it on my own, on that particular occasion I just didn’t fuckin’ feel like it. It seemed likely to be so tedious.
Was disappointed to find what I found behind it, because that would have been much more satisfying had I solved it myself. 
Only played a bit, but I advanced down another floor and was able to get to this puzzle, which I’ll spoiler-box because the solution shown here may be right(I can’t remember my own solution even 1 day later).
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My wife and I did solve it and it was exhilarating.
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I swear…the rules were not adequately obvious.
Tetris shpaes in the big floor-panel did not have to remain in the same quadrant as they were in the individual panels. This was counter-intuitive, even though it is clear this is the only way to make it symmetrical.
We then advanced to the double-doors and prayed for a miracle.
We solved the right door, a separation-color puzzle, on the first try. The left door, a star-tetris puzzle, was almost impossible. I swear not every iteration was solvable. I am almost positive we could not solve 80% even with 30 minutes to work. We got lucky and an easier one came up.\
We are working on pillars now. Looks like we have reached the end. We’ll see how it goes.
Beat it today. Loved it. Hardest game I’ve ever finished. My finest gaming achievement.
Yay!
Now, here’s the thing.
Spoiler, but you’re going to want to read this:
There’s a good chance you haven’t really beaten the game
Increasingly revelatory hints on a single topic to follow:
Remember how you could have turned left instead of right under the windmill, if only that door hadn’t been locked from the other side?
You actually only needed 7 lasers to get into the mountain. What were the other four for?
Did you notice the statue of the kid(? I think it was a kid?) solving a puzzle on the ground just before the door to the final pillar puzzles? Did you solve his puzzle?
There was a cord leading up to that kid’s puzzle. How do you light it up?
This one comes as close to giving everything away as I dare:
The guy carrying the box at the top of the mountain–take a closer look at the box
Yes, I know. I guess I’m wimpy, even having solved the 11 lasers and final area, but I consider the elevator to be the ending. Yeah, I may go back to try more, but I consider that more bonus than real ending.
Cool beans, just making sure you weren’t unintentionally missing out. 
Do you also know about the ending you can get to just a couple of minutes after starting the game?
Yes, I walked out and viewed it once the game was over and re-began.
Better than the actual ending. It felt like the way I feel. Seeing circles and lines everywhere, trying to still solve puzzles.
I’m pretty sure the Witness is my game of the year for 2016. I can not remember such a satisfying accomplishment in gaming. Beating this game with just me and my wife was some of the most fun we’ve had in a long time. Our notebook is pretty detailed. I liked looking back on what we did not know or understand at the beginning and seeing how we are able to understand everything now.