Which puzzles with chess board must be on-topic here?

There have been several questions on meta recently that bring up a similar topic, but I would like to formulate the question explicitly here:

Which puzzles that use a chess board are on-topic here?

To make the answer easier, I would like to divide such puzzles into several groups:

1. Puzzles that use a chess board only, like covering chess board problems, for example The Mutilated Chessboard. Or cutting chess board problems.

2. Puzzles that use a chess board and modified chess pieces. That means pieces which moves differently from usual 6 types of chess pieces. For example, The Bunny's Tour, How Many Speedy Knights on a Chess Board?.

3. Puzzles that use a chess board and chess pieces (including the rules of their movements), but do not care about the game itself as a set of moves leading to a win or loss. For example, How many queens can be on a chessboard without attacking each other?, How many squares can 4 queens control?, How many chess pieces does it take to "cover" all spaces on a chessboard?, Most moveable chess position, Optimal strategy against a random opponent, Find the shortest chess game with 18 queens?.

4. Puzzles that use a chess board and chess pieces and full game rules, but ask questions that are not really useful for chess players, but interesting from a rules investigation point of view. For example, What is the position in chess with the longest string of moves before mate?.

5. Retrograde analysis chess puzzles. These can help you to learn to play chess on some level (unlike the previous category), but they ask for questions, that never arise during real chess games because there you know all previous moves. Also, they usually provide chess positions that would never appear in a real game. For example, Is there a retrograde analysis puzzle like "Point on the incorrectly drawn chess piece"?, Find the color of the chess pieces

6. Traditional chess puzzles, like "White wins in 2 moves," "White starts and wins."

Also, we have chess tag already, so another question is: Which type of puzzles should be tagged with the tag and which should not? Maybe some less-chess-related puzzles should be tagged differently, like the puzzles in category 1.

My personal opinion on on-topic questions is:

A) Category 1 must be not only allowed, but desirable here. These are the puzzles in their the most common and interesting sense.

B) Categories 2-4 must be for sure acceptable here. These are puzzling questions, and they do not have other good place on SE.

C) Category 5, retrograde analysis chess-puzzles. It is hard for me to decide. Unlike previouse categories there are a place for them on Chess.SE, they have a special tag for it, but it is not very actively used and Chess.SE is still in beta and it is unclear what will be on it and what will be not. Also I think these are still beautiful puzzles, which I am interesting in solving though I am not interested in chess game itself.
If I would be the only one to decide and would be forced to do it I would say that this category should be on Chess.SE, not here.

D) Category 6 must not be here, they are for Chess.SE for sure. This is 100% about the chess game and for chess players.

Concerning tags usage:
I think it would be appropriate to tag categories 2-6 (those that would be on-topic) with tag "chess". For category 1 I propose a new tag "boards", that would include also puzzles with not-standard boards, like 4x4, NxN. EDIT: See .

• Totally agree. People's concern is probably about the infinite nature of these problems - there are infinite variations on these that can be created (someone cited the posting of Sudoku positions). Commented Nov 4, 2014 at 12:51
• It's worth noting that there's a difference between being on-topic and being good-quality - while these questions may be on-topic here, they might not all be of acceptable quality.
– user20
Commented Nov 4, 2014 at 16:25
• @Emrakul and for low quality, downvotes are the only solution, so say if I feel its bad and someone else feels its good, that will determine if its low quality or otherwise, am I interpreting it right?
– skv
Commented Nov 5, 2014 at 2:47
• @skv Yes and no. I wish it were that straightforward. While voting does serve as an indicator of what people like, it doesn't necessarily serve as an indicator of what's on topic. It's important that our first goal is to create a helpful resource for people online, as that's what Stack Exchange is about: good Q&A. It's a good rule of thumb that people tend to vote how they feel, and while frequently that's aligned with our topic goals, sometimes it isn't. They're two different systems. Totally appropriate to let votes raise the issue of on-topicness, though.
– user20
Commented Nov 5, 2014 at 2:51
• @skv: If there are so many puzzles of a certain type that people get tired of them, the number of upvotes for such puzzles will decrease and the number of downvotes will increase. If people are primarily inclined to post puzzles when other similar puzzles receive a favorable mix of upvotes and downvotes, that would suggest that the mix of puzzle types people would adapt itself according to what people would like to see. Commented Nov 14, 2014 at 19:17