Freshly Frosted is the second best linepath game I've played, behind just Cosmic Express. With the exception of level 9-12, I found the puzzle design to be excellent. I'm even willing to concede there was likely a catch to 9-12 that I overlooked. I really can't be mad at this game.
The atmosphere of Freshly is beyond chill. I never felt frustrated, even on the handful of puzzles that had me stumped for a while. There are always some moves you can make with absolute certainty and, with some thoughtful experimentation, the rest of the solution can be sorted out. The narrator may not be to everyone's taste but I loved them. The dialogue at the start of each level is extremely ridiculous--think ASMR Youtube video vibes except it's someone talking about donuts. The music is pretty good too; the way it evolves as you start running your bonkers donut contraption is quite pleasing. The overall atmosphere is one of the best I've encountered in any puzzle game.
Difficulty is never intense. At the same time, it's not a pushover. I believe a few levels took me over an hour to complete. You cannot solve these puzzles with brute force or haphazard experimentation. Some of the later levels will require fairly strong methodical analysis. New mechanics are introduced every 12 levels out of the 144 total, so the game feels fresh(ly) right up to the end.
FF is a lovely game all around that I enjoyed far more than I expected. I found the challenge to be perfect for keeping the player mentally involved, while never requiring the all-consuming attention that a game like Cosmic Express often does. Puzzle fans of all skill levels will enjoy this game. Even Cosmic Express graduates.
P.S. look up Delicious Donuts if you seek a very difficult donut puzzler. The spatial logic challenge of DD is on par with Stephen's Sausage Roll. Every solution is a huge victory.