Phos4

Phos4 is a pure-bash, themeable terminal-UI engine — gradient-swept wordmarks, arrow-key pickers, panels, spinners, progress — shipped as a single file any CLI script can source. No curses, no Python, no npm — bash 3.2 and ANSI escapes, nothing else.

It exists because the look outgrew its birthplace. A3K — the Y3K design language — took shape inside the Project System, entangled across three scripts; the installer even carried its own duplicate copies of the animations. Good enough to reuse, too tangled to travel. Phos4 is the extraction: the engine (mechanics) pulled clean of the look (data), so the machinery is shared once and the look is swappable per consumer.

The verbs stay disciplined: a surface wears A3K; Phos4 is fluent in it and renders it. An engine never builds the look — “built” stays reserved for the tagline, Built for the year 3000.

The architecture is one clean cleave, three roles. The engine owns the mechanics — how a gradient sweeps a ramp across characters, how a wordmark gets boxed in rails, how a picker repaints in place. A theme is pure data — colour indices, gradient stops, rail glyphs, literal wordmark rows — no rendering code in a theme, ever; the contract is locked. And the consumer — the script that sourced the file — owns choreography: what happens, in what order, is its business. How it looks is not.

That table is the theme side of the seam — swap the prefix and you’ve named a new theme; the engine dispatches through PHOS4_THEME and never knows the difference. The seam is proven, not promised: a second theme — a different brand with its own logo language, flat colour, single-line box — renders through the same engine with zero engine changes. The one gap it exposed (a hardcoded ║ side glyph) was closed by promoting that glyph to theme data; the pure-data contract held, no escape hatch.

Even greyscale is data: PS_MONO=1 swaps the ramp for a mid-grey band and the engine renders on, colour-blind — that’s the toggle under the demo above.

The API is small, and all of it is namespaced: source one file, get every phos4_* call. Prompts answer the bash way — through environment variables and exit status, never parsed stdout — and ESC always means no.

Half of Phos4’s value is invisible: the accumulated rules that keep a pure-bash renderer from corrupting a terminal. They live as comments at their site in the engine — no external doc to consult — and every one of them was paid for.

Extraction invites drift: rewrite the machinery and the look shifts a shade. Phos4’s acceptance bar refused that — byte-identical output, enforced by a golden master: renders captured from the original source before extraction, and every engine render since diffed against them, raw ANSI and all.

Twenty-seven captures — banners, pickers, panels, both themes, colour and mono — all green. Vendoring the engine back into the Project System deleted ~960 lines of duplicated look from its first consumer, and that consumer’s release script re-copies the built engine every time it runs — a stale copy can’t ship.

Authored split, shipped single. Source is an engine plus one file per theme; the build is a concatenation — this is bash, and the build step is a cat with opinions:

Consumers copy dist/phos4.sh into their own repo and source it. Zero dependencies, nothing to install, no version to negotiate — the file that ships is the whole engine:

Three environment variables drive everything: PHOS4_THEME picks the theme (default y3k — the A3K look), PHOS4_ANIMATE=1 opts into the power-on entrance, and PS_MONO=1 goes greyscale.

Phos4 has no public repo and no standalone download — yet. Today it ships the way it was always meant to: vendored inside a consumer. The Project System kit carries it as bin/phos4.sh, rendering the dashboard, the lifecycle scripts, and the installer. A standalone kit in the Blue Steel mold is planned — and until something actually ships, this page stays a read.