Hi CDJimmy, thanks for your interest in Chord! To answer your first question, as far as I know this logic does not exist in any other game. I created everything (the logic, rules, algorithms, puzzles, etc...) in this game myself.
If I'm understanding you correctly, your concern is that some puzzles have multiple solutions, or no solutions. The way the game is intended to work is that each puzzle should only have 1 possible solution. I took a look at the images you provided, and it looks like they do not follow all of the rules. Each puzzle in the pictures you provided break the same rule:
"Each number on one half of the circle must be the same as a number on the opposite half of the circle that it's line intersects."
Basically, a line coming from a number on top must intersect a line coming from the same number on the bottom. I added to your screen shots to show where this rule is being broken.
Picture A:
The line coming from the 2 on top, does not intersect the line coming from the 2 on bottom. Same with the 6s.
Picture B:
The line coming from the 3 on top, does not intersect the line coming from the 3 on bottom.
Picture C:
The line coming from the 2 on top, does not intersect the line coming from the 2 on bottom. Same for the 1s, 3s, and 6s.
Picture D:
The line coming from the 3 on top, does not intersect the line coming from the 3 on bottom. Same with the 1s and 6s.
As for the solution picture, the reason it is a correct solution is because it follows all of the rules.
1 through 6 on the top.
1 through 6 on the bottom.
No lines have the same number on either end point.
Ever number on one half of the circle intersects the same number on the other half of the circle.
Hopefully that makes sense, and answers your questions. Please let me know if I missed something. I appreciate the feedback, I'm always looking for ways to improve.
Thanks again for playing the game! Let me know if you have any other questions.
Oooh ok ^^ than you I understand ! it's better like this lol. I'm not english so maybe it's just my own mistake.
The reason why I failed in this rule is in the tutorial. In explanations 6/10 and 8/10 you saied :
"the line only intersect...".
In first I understood this rule apply only if 2 lines intersect but not it they are more than 2.
That's why in my example I fill out numbers 5 and 4 because this line only intersect with 5 and 4.
I understand now ; if only 2 line intersect you know wich number to put inside. BUT if there are more intersection the rule stay the same ^^
So I can't judge with my non-English reading. But peraps the "only" explanation could be made more excplicit.
Hope it's help ;-) I know feedback is important and most people never notify when they find problems.