Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add majiayu000/spellbook --skill ascii-backdropgit clone --depth 1 https://github.com/majiayu000/spellbookWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/majiayu000/spellbook/ascii-backdrop)<a href="https://agentmods.dev/skills/majiayu000/spellbook/ascii-backdrop"><img src="https://agentmods.dev/badge/skills/majiayu000/spellbook/ascii-backdrop/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/majiayu000/spellbook/ascii-backdrop"><img src="https://agentmods.dev/badge/skills/majiayu000/spellbook/ascii-backdrop.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00209 | $0.03239 |
| Opus 5.5 | $0.00084 | $0.01296 |
| Sonnet 5.5 | $0.00042 | $0.00648 |
| Haiku 4.5 | $0.00021 | $0.00324 |
Grade A, and why
ascii-backdrop scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 9d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 148 lines — stays where its author put it; the contents beside it link to each section on GitHub.
ASCII Backdrop
A subject paints brightness or colour on a small canvas; the engine prints every character cell as a glyph, dot or tile. Anything that can paint on a canvas can be the subject.
How it works
Every frame, each layer's subject draws itself on a small offscreen canvas (a few pixels per character cell). The engine reads those pixels and prints them in the layer's mode. A lower depth dims a layer, which gives depth for free; a clear zone fades output around the UI so headings and inputs stay readable. Changing the subject means changing one draw function; the engine does not change.
| Print mode | Layer setting | Look | Frame cost at 1440×900 (measured) |
|---|---|---|---|
| Brightness glyphs | default mode: 'glyph' |
Glyph from the density ramp; the brightest cells print as filled boxes | ~8 ms |
| Edge glyphs | glyph: { edges: true } |
/ \ | - follow strong edges |
~8 ms |
| Shape matching | glyph: { match: 'shape' } |
Samples a 2×3 grid per cell and picks the glyph whose shape fits best, for crisper outlines (after Alex Harri) | ~5 ms (cached) |
| Braille | mode: 'braille' |
2×4 dots per cell, twice the resolution, optional Bayer dither | ~6 ms |
| Dither | mode: 'dither' |
Bayer 4×4 ordered dither, dots or squares sized by level | ~6 ms |
| Colour tiles | mode: 'tile' |
Rounded squares in the colours the subject paints | ~3 ms |
Subjects paint in white (brightness = density); only tile layers paint real colours. Layers in different modes can share one scene.
Files
assets/ascii-backdrop.js: engine, built-in subjects and page helpers, no dependencies, exposed aswindow.AsciiBackdrop. Copy it into the project.assets/demo.html: a dark prompt page with the backdrop behind it; switch subjects, print modes, glyph sets, CRT and palettes; the heading decodes; a corner card shows the image dissolve; upload an image or video.scripts/check.mjs: screenshots desktop, phone and reduced-motion views and reports errors and frame rate (needs Playwright).
What ships with it
4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 9d ago First seen · 148 lines · 209 tokens per session scan A c1b4cbddab35
ascii-backdrop is a skill published in the GitHub repository majiayu000/spellbook (290 stars, last pushed 2d ago), licensed MIT. It adds 209 tokens to every session and 3,239 once invoked, about $0.0008 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-10-29.
ascii-backdrop compared with skills from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| ascii-backdropmajiayu000/spellbook | Skill | 290 | 2d ago | MIT | A | 209 | Claude Code, Codex |
| cao-session-managementawslabs/cli-agent-orchestrator | Skill | 1.5k | yesterday | Apache-2.0 | B | 83 | Claude Code |
| workflowzhinkgit/embeddedskills | Skill | 785 | 18d ago | MIT | A | 88 | Claude Code |
| pneuma-sessionpandazki/pneuma-skills | Skill | 161 | yesterday | MIT | A | 127 | Claude Code, Codex |
| fast-resumeangristan/fast-resume | Skill | 190 | yesterday | MIT | A | 50 | Claude Code, Codex |
| lov-organize-storagelovstudio/skills | Skill | 72 | 3d ago | MIT | A | 58 | Claude Code |
| lov-finder-actionlovstudio/skills | Skill | 72 | 3d ago | MIT | A | 36 | Claude Code |