"Roboto Mono is the engine's monospace font"

Your UI uses font-family: "JetBrains Mono" or font-family: Consolas for a monospace look. It works on your dev machine but falls back to a proportional font for other players.

The s&box install ships ~65 fonts at addons/base/Assets/fonts/: Inter, Poppins, Roboto, Roboto Condensed, Roboto Mono (all weights), and Material Icons. Nothing else. "Consolas" only resolves because it's a Windows system font; "JetBrains Mono" only resolves if you've installed it locally.

s&box has no @font-face support. It auto-registers any font file under an Assets/fonts/ path by its internal family name, and SCSS references it by bare name.

For a monospace look with zero extra work:

font-family: "Roboto Mono", monospace;

Engine precedent uses this exact pattern (e.g. the menu addon's stat-value styles).

Shipping a custom font

To use an actual custom TTF (e.g. real JetBrains Mono):

1. Drop the .ttf files into your project's Assets/fonts/ directory.
2. Reference by internal family name — no @font-face declaration needed:

font-family: "JetBrains Mono", "Roboto Mono", monospace;

The font resolver walks registered font files, not the OS font directory. Only fonts physically present under an Assets/fonts/ path are available at runtime — and font-family is glyph-corruption-safe (unlike font-size, which has its own rendering traps).