Increase the distinguishing factor of "z" glyphs internally and to "n"

[mehmetoguzderin]

Increase the distinguishing factor of "z" glyphs internally and to "n" glyphs.

First of all, I would like to thank you for maintaining this project; the presence of Noto Fonts helps tremendously every day.

During our recent research (some of which were already published last year), Noto Sans was essential to facilitate certain Old Turkic script studies in digital form. Although Noto Fonts' representation of Old Turkic glyphs is mostly good, the Orkhon Z and Yenisei Z glyphs could benefit from improvement. Currently, Orkhon Z does not use the "default" or base form usually presented in modern textbooks or reference materials on the subject. While the Yenisei form is better it could represent the curved shape. There are two problems:

• The Orkhon Z glyph's distinguishing factor from both Orkhon N and Yenisei N would benefit from having an increase, especially in lower resolution or visual impairment.
• Yenisei Z could better represent the nature of Yenisei corpus.

When it comes to Old Turkic script, there are three essential corpora: Orkhon (or including other larger inscriptions), Yenisei (or more fragmentary inscriptions), and inked. The current Orkhon Z form, where the lowered arm is on the left side, is never found in inked form and is only a subset of Orkhon forms; however, the inclusion of that form found in a subset makes it easy to confuse with "N" easily (especially inked materials' N looks almost like the N in current Noto Font design). Nevertheless, simply rotating it would make the shape the same for Yenisei and Orkhon, so the Yenisei form can better represent the curved nature of the letter since such form is more attested in fragmentary inscriptions.

I have created a PR in this direction based on existing data: #6

I suspect the current design is probably inherited from the Old Turkic document in Unicode. However, the study of the script saw a meaningful increase in studies since the initial production of that document and its predecessor reference studies.

A reference listing of Old Turkic script letters: https://www.runiform.lingfil.uu.se/wiki/Glyphs

I can refer to further resources (or help facilitate dialogue with experts of the script); however, I believe the existing references should help to demonstrate this simple change in Orkhon Z and Yenisei Z increases distinguishing factor from Orkhon & Yenisei N for ease of readability and also representation of underlying corpus of each respective form.

Thank you very much for your consideration.