In response to the question asked in the loop puzzles post, there are various strategies that can be used when solving loop puzzles. Many of them are perhaps obvious, and also quite a few are hard to explain in text only format!
However, the most obvious one is to mark in the loop in any square where the movement of the loop through that square is forced.
If there is a square that only has two possible exit/entry routes (out of a maximum possibility of four) then the path of the loop can be marked straight away, as of course every cell that is part of the loop must be both entered and exited.
This means that any corner cells you know to be part of the loop (which on occasion you may not such as in yajilin) can instantly have the loop marked in. In simple loop finder puzzles, this is always the case.
Usually there will be other cells where this applies too, for instance if there are any black cells marked or any paths etc check the cells around them or between them as often these must have the loop pass through them.
Remember that if a loop goes into an area, let's say inside a 'U' shape, then the loop has to pass back out again, so there must be a gap at least two cells wide for the loop to go in and then come back out.
Often if you have a small almost closed area in the puzzle but for one other loop end that you are not sure as to whether it joins the others or not, you can count the loop ends to see.
You'll need to have an even number of loop ends in any isolated section, if there is an odd number then there will always be a part of loop that cannot join up. So counting odd/even sections of loop going into/out of a section of a puzzle can be a useful thing to do.
And finally, and fairly obviously, if any move would result in another square not having both an entry/exit cell and you know that other cell must contain the loop, then that move is not valid.
There are no doubt lots of other rules, these are just some that spring to mind.
If you have any other strategies for solving loop puzzles then please post them here, whether something like simple loop or one of the loop puzzles with more rules and features.
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