The upper bound really should be in the description.

Seems like image links are dead.

Please make python tests not useless - obligatory solution.

Feel free to fork it and do improvements, nowadays I don't have time to do this.

100 is plenty, you can go to 89 and probably less with more obscure imports.

The - in the description (e.g. Z(N) - sum of all S(i)) is unfortunate as separator since it looks like, well, minus.

I think much easier than trying to convey meaning in words, would be to replace unrelated graphic with one showing the example mentioned above.

Better question yet, how come both are ranked 6 kyu?

You're right, they can't fit at once, but the task is underspecified not saying that overlapping is ok.

Why this kata 'frustrates' is that the description's too suggestive that there's some very specific piece of code requiring all allowed characters rather than more generic solution.

The coordinate system around the plane is the same as in the plane.

There are invisible slashes outside, you're welcome.

Nope, out of recently completed katas rated most as 'somewhat', apart from maybe two, which received 'none' (in both cases I found the kata ideas and design poor and questionable) which with low amount of votes and my voting multiplier brought percentage down, but not in any case have I voted out of spite or some personal grudge (I don't have any with anyone) and after all it should be a drop in a sea if majority of users are satisfied with the task.

Yeah, sure ok.

That it isn't standard way of handling arrays, and best practice approach is preferred on cw while authoring / translating kata, to the point where plenty of betas have issues raised over stuff like this.

Any sensible reason for nulling arrays instead of passing size?