the symptom, in your words

"Roboto Mono is the engine's monospace font"

✓ verified on 26.07.08e

lane Building UIposted Jul 11, 2026updated Aug 1, 2026

▸ SYMPTOM

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.

▸ CAUSE

The s&box install ships ~65 fonts at addons/base/Assets/fonts/. "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. Fonts under an Assets/fonts/ path are referenced by internal family name, and SCSS references that name bare or quoted.

Corrected 2026-07-31 (engine 26.07.22): "auto-registers any font file under an Assets/fonts/ path" is too broad. Roboto Condensed, though it physically ships at addons/base/Assets/fonts/ alongside the others, is not reachable from UI CSS. Verified live, font-family: "Roboto Condensed" (and unquoted) silently falls back rather than rendering condensed glyphs. The engine's own SCSS only registers Poppins, Roboto, Roboto Mono, Inter, and Material Icons as usable UI families. A font file being present in the base install's fonts folder is necessary but not sufficient; treat the confirmed-reachable list as exactly those five until a family is proven live by an actual capture, not by its presence on disk.

▸ FIX

For a monospace look with zero extra work:

snippet

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):

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

snippet

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

▸ WHY IT WORKS

The font resolver walks registered font files, not the OS font directory. Being physically present under an Assets/fonts/ path is necessary but not sufficient: the family also has to be registered by the engine's own SCSS, which is why Roboto Condensed ships yet never resolves. Prove any family you rely on with a live capture rather than a directory listing.

Verified on engine 26.07.08e: seen in a real project.

s&box moves fast; an undated fix is a liability. Spot a stale detail?

SUPERSEDED: the font-size-declaration-count theory below was owner-settled (26.07.22) to be a CAPTURE-PATH artifact, not a real render bug. Panels with these exact font-size declarations render pin-sharp on the physical screen. Never strip font-size from a shipping stylesheet to 'fix' captures. See camera-screenshot-cannot-verify-fonts.

Building an s&box HUD

One ScreenPanel host, static UIState for modals, self-closing panels, toast stack: BuildHash every flag the markup reads.

My s&box UI won't update / is frozen

BuildHash() is the only re-render trigger: hash everything the markup reads, including collection contents and flags.

changelog

Aug 1, 2026Corrected (26.07.22): 'auto-registers any font file under Assets/fonts/' is too broad. Roboto Condensed ships but is not reachable from UI CSS; the engine's own scss registers only Poppins, Roboto, Roboto Mono, Inter and Material Icons.