Warning! This guide contains spoilers!
5 Star Logic Puzzle Solution
All credit goes to TNTDragons!
Location
At the top of the highest temple in Serene Deluge. Highest spot in the (mainland) world essentially.
How to Solve
I think this puzzle is intentionally the hardest in the entire game. Deserves 6 stars. If it’s any consolation, I shared the solution with friends when I finished it, so I can confirm that you’ve not made a mistake from what I can see (though I could’ve easily missed something).
Overall, I would advise against using the strategy of “Let’s assume cell is X, and see if it leads to a contradiction”. More often than not, the contradiction will come way down the line. I made a mistake at some point in the puzzle, and only reached a contradiction 30 minutes later, with dozens more cells filled in. had to re-do it from scratch essentially, only to then do a mistake later again, and having to roll with fixes “Live” (I made it a rule for myself to not use foresights). That’s not to say that trying this every now and again won’t be helpful, but as you correctly noticed, most puzzles in the game will only require you to look a few steps ahead, so don’t go further than that.
That being said, you can try filling in the board just semi-randomly. This will give you information about which areas are more problematic than they might seem, and which are more malleable. You can then look around those areas and try and logic your way into pushing them forward a bit.
Another tip is to try and use broader strokes. Rather than “If I color this cell X then this other cell would have to be Y” try and doing more general ideas of “if I color this cell black, then this light cell has to travel through Y to connect to the rest of the grid”. Admittedly you will still need to think about individual cells, but it’s less about solving the puzzle and more about thinking forward to try and find the cell that has the shortest time to a contradiction.
Finally, I realize this only now, but there is a certain… “hidden rule” that might make this puzzle 10 times easier. I recommend checking the star structure underneath the southern edge of Autumn Falls or just look through your Insight Encyclopedia if you want.
And if you’re too lazy, then read the spoiler below:
The existence of “All light cells are connected” and “all dark cells are connected” at the same time results in a 2×2 checkerboard pattern to be impossible.
To me, this was the hardest puzzle in the entire game, so keep pushing and hopefully you’ll get through it all!
If you ever see a situation in these logic puzzles where you’re saying “If X is true, Y doesn’t matter”, then X is false.
This is actually something I consider as the highest level of “insight” you can have. The rule of “One and only one solution exists”. It’s extremely easy to mess up, and I remember I had to use it to get out of fixing a simpler mistake I made earlier. However, I don’t think you need to use this rule to solve any of the puzzles, though it can make some easier (I use it all the time to speedrun puzzles in the mainland)
The shortest way that I see to determine that a dark cell doesn’t work there is that if it was dark, the cell above the 6 would have to be light. If that was light, the cell to the left of that could be dark or light, since nothing else constrains it (it’s not cutting anything off, and it isn’t in view of any of the viewpoint number cells.
I remember that one being a pain. While it’s usually good, I found for this puzzle that Foresight doesn’t always give you the next most reasonable deduction. That one in particular I also found weird.
To add to this, there are two 5 star puzzles on top of that temple and this is the one on the eastern side. It’s technically not at the absolute top, but it’s on one of the highest ledges that has a horizontal surface to stand on. It might be possible to get up there without super jump, but I couldn’t find a way.