Handmade puzzles, i.e., puzzles crafted intentionally by a real person almost never require guessing. However, a lot of “extreme” difficulty puzzles (or similar difficulty terms) in apps, newspapers, puzzle books, etc. are not handmade by a real person, but computer generated. There’s probably a logic chain that’s like 15 steps long that humans couldn’t reasonably follow, but a guess is likely faster and more enjoyable.

Someone else recommended Cracking the Cryptic on YouTube, which is a great source - the daily puzzles are nice because you can follow along in the video if you’re stuck, but they also have lots of apps with Sudokus that never require guessing. Another good source is Logic Masters Germany, which has lots of handmade Sudoku and other puzzles: https://logic-masters.de/

What counts as an “older game?” Surely not… thinks about the games I played last week …Tie Fighter or Dune 2?

Yeah, hopefully there was a control done with just water (no tea) at the same temperature also passed through the second filter. I can’t seem to get the whole paper without a subscription (or school/work/library account). Anyone have access and can confirm the details?