A line has start and end. Let's call them A and B. And sometimes the line is "valid" (by my Kata rules) in one direction only. e.g from A-to-B, or from B-to-A, but not both at the same time.

But being valid in one direction only is sufficient to call the whole line "valid".

So Sometimes a line may be valid in one direction but not the other. Such a line is still considered valid. means:

• valid A-to-B, but not B-to-A ==> line is valid
• not valid A-to-B, but valid B-to-A ==> line is valid
• valid A-to-B, and valid B-to-A ==> line is valid
• not valid A-to-B, and not valid B-to-A ==> line is NOT valid

I suspect part of what's confusing people in this kata description is "Sometimes a line may be valid in one direction but not the other. Such a line is still considered valid."

I think, but am not sure, that you mean "Sometimes a line may be valid when starting from one endpoint, but not the other. Such a line is still considered valid". I think you do not mean something like "Sometimes a line may be valid if you take one turning at a +, but not a different turning at a +. Such a line is still considered valid". (Viewed narrowly, I think that'd be a reasonable interpretation, but it's hard to make sense of given the other rules.)

Right?