(Note: Continued LJ outages and my own lack of time from starting a new job this week are making consistent posting difficult. I'm tempted to start a Saturday Stumper series, but for the next many months expect Friday* Puzzles when my web service and my job allow them.)
When the instruction booklet for my Double Decathlon test was released, this was the puzzle that seemed to cause the most discussion. Mainly over whether this is Yajilin or not. My opinion is that Yajilin's default style relies too heavily on clue squares, particularly instantly definable clue squares, and you cannot block off a lot of starting cells without adding clues that can compromise a puzzle. I feel that a presentation with some clues but also just some unusable squares makes for a more balanced puzzle type that emphasizes many other loop forming strategies (like Simple Loop) instead of just square counting strategies. Almost Simple Loop is this compromise puzzle presentation. Both of these puzzles went a bit outside the typical Yajilin playbook, and neither could have easily been achieved at the target difficulty if I had to add in extraneous clues to block off the starting geometries, so I am comfortable saying neither is a Yajilin.
TL,DR: Check over the possibly familiar rules and enjoy the puzzles.
Draw a single closed loop that passes through adjacent white cells and not through any gray cells. The loop cannot intersect or overlap with itself. Some white cells may not be a part of the loop, but no two unused white cells can share an edge. Some gray cells contain a number and arrow indicating the count of unused white cells in the direction of the arrow.
Example and Solution:
Not too much to give away on these puzzles except that there are in both cases some long channels that must contain part of the loop and the challenge then is fitting in a valid loop without isolating ends while at the same time satisfying just a few of the given clues (none of which are of the usual style of 1+arrow with just 1 cell it points to which I h-a-t-e hate as two gray squares achieves the same instant grid division that is meaning to accomplish without any logic).
In the hard puzzle, the key area to visualize possibilities are what I'll call the two "square rooms with 4 doors" in the upper left corner and lower right corner. You can enter and exit these either once or twice but the consequences of doing so need to be carefully mapped to get started.