# OPERATOR Mono Prototype · 0.001

A real, experimental Regular (400) font proof: Geist Mono's proportions and
readability with selective, square returns on lowercase y, j, t and l.

This is a modified version of Geist Mono Regular 1.700, not a wholly original
typeface. Original font copyright 2024 The Geist Project Authors
(https://github.com/vercel/geist-font). Modifications copyright 2026 OPERATOR
contributors. Both are distributed under the SIL Open Font License 1.1; see
OFL.txt. Space Mono informed the design discussion; no Space Mono outlines or
font data are included.

## Design

- y: a rounded upper bowl drawn from the inherited u, with a vertical descender
  and a square, horizontal left return. The 90° corner is the signature detail.
- j: a square left return, preserving the inherited dot and top bar.
- t: a square foot with the inherited crossbar and ascender.
- l: a square top bar; its broad baseline serif stays distinct from I and 1.
- Dependent accents inherit the modified bases. The alternate l and barred t
  also receive square returns. Original round counters, numerals and unrelated
  outlines remain intact.
- The dot below y is centered beneath the new return, with matching combining
  mark positioning, to keep the dot separate from the descender.
- 1000 units per em, 600-unit Basic Latin advances, 530-unit x-height and
  710-unit cap height. Vertical stems are 84 units; horizontal strokes 74 units.

## Scope and limits

This is one experimental weight for visual review, not a production typeface
release. The source's 889 mapped codepoints and OpenType features are inherited;
Basic Latin is the reviewed repertoire. Inherited languages and alternates have
not had a comprehensive linguistic or visual audit. The modified glyphs and
their dependent composites have no manual hinting. Other source hinting is
retained. Further spacing, hinting, language coverage and cross-platform checks
are needed before production adoption. There is no bold, italic or variable
font in this proof; do not synthesize these styles.

The application continues to use its established production typography. The
proof is isolated to /docs/foundations/operator-mono, with an unmodified Geist
Mono comparison, editable sample text and real-size 12/14/16px readouts.

## Build and verify

From the repository root, using Python 3.11 or newer:

    python3 -m venv .release/typeface-venv
    .release/typeface-venv/bin/pip install -r typefaces/operator-mono/requirements.txt
    .release/typeface-venv/bin/python typefaces/operator-mono/build.py
    .release/typeface-venv/bin/python typefaces/operator-mono/verify.py

The checked-in upstream TTF is pinned by SHA-256. Build.py contains the source
geometry, records provenance, renames font identity fields, strips stale hints
from changed glyphs and their composites, and emits reproducible TTF and WOFF2
files. The docs public directory also contains a ZIP with the prototype fonts,
this note, provenance and the full OFL. Keep the attribution and license with
redistributed files.

Source: https://github.com/vercel/geist-font/tree/10dc7658f13c38a474cde201bb09a4617267545b

Generated files: apps/docs/public/fonts/operator-mono/
