Borrowing it
Nothing to install: this file belongs to vchelaru/FlatRedBall2. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/vchelaru/FlatRedBall2/main/.claude/skills/animation-editor/SKILL.mdgit clone --depth 1 https://github.com/vchelaru/FlatRedBall2Wrote 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/vchelaru/flatredball2/animation-editor)<a href="https://agentmods.dev/skills/vchelaru/flatredball2/animation-editor"><img src="https://agentmods.dev/badge/skills/vchelaru/flatredball2/animation-editor/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/vchelaru/flatredball2/animation-editor"><img src="https://agentmods.dev/badge/skills/vchelaru/flatredball2/animation-editor.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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 | $0.00054 | $0.03117 |
| Opus 5.5 | $0.00022 | $0.01247 |
| Sonnet 5.5 | $0.00011 | $0.00623 |
| Haiku 4.5 | $0.00005 | $0.00312 |
Grade A, and why
animation-editor 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 today.
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 — 118 lines — stays where its author put it; the contents beside it link to each section on GitHub.
AnimationEditor — Location & Layout
The AnimationEditor is the desktop tool that lets users edit .achx animation chain files (frames, regions, shapes, onion-skinning, preview playback). It is being rewritten on top of Avalonia and lives inside this repository at:
tools/AnimationEditorAvalonia/
The product name is always AnimationEditor, one word, in UI strings, docs, comments, and PR text. Never write "Animation Editor".
The legacy WinForms version (
FlatRedBall.AnimationEditorForms) lives in the separateFlatRedBall(FRB1) repo atFRBDK/FlatRedBall.AnimationEditorForms/. Do not edit it for FRB2 issues — that codebase is being replaced. Issues filed invchelaru/FlatRedBall2always refer to the Avalonia version.
For writing tests against the editor — headless Avalonia, service wiring, the [AvaloniaFact] deadlock pitfall — see the animation-editor-testing skill. Before changing editor behaviour, dogfood it headlessly through the harness in tests/AnimationEditor.App.Tests/Dogfood/ (README there); it drives the real window with simulated input and never touches the desktop. Any visual change needs before/after screenshots shown in the chat; the animation-editor-screenshots skill covers that and doc-page screenshots. For SkiaSharp rendering internals and performance debugging, see animation-editor-rendering. For Tiled .tsx support, see animation-editor-tiled.
.achx is a general-purpose format — the editor authors, runtimes interpret
.achx is not an FRB2 file. It is a general-purpose animation/atlas format consumed by several runtimes that each render it their own way: Gum (across its Skia, raylib, and sokol.net backends), MonoGame/KNI/FNA, FRB1 (custom-shader rendering), and FRB2 (SpriteBatch). The editor authors the format; each runtime decides what to do with the data. This frames every feature decision here:
- A field the editor exposes does not obligate any runtime to apply it. Store the data in the format; whether a given runtime renders it is that runtime's choice. Do not gate adding a frame field on FRB2 (or any single runtime) implementing it — e.g. per-frame
Eventsare stored in the format, and Gum and FRB1 ignore them. - The preview is a reference rendering, not a per-runtime contract. The bottom panel renders with SkiaSharp (
PreviewControl,SKCanvas/SKColorFilterinDrawFrameCore), so it will diverge from what a MonoGame/FNA/FRB1 runtime produces for the same file. That divergence is inherent to a general-purpose tool and is not a bug — pick a sensible canonical interpretation. "The preview might not match a runtime" is never a reason to withhold an authoring feature.
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.
- today Changed · +2 lines 6af319ebda6b
- 9d ago Changed b40749e774ec
- 10d ago Changed · +6 lines 995e2ca0f66f
- 12d ago Changed · +4 lines 980f4c98dbfc
- 16d ago Changed · +54 tokens per session dbe1c061da56
- 18d ago Changed · -1 lines 9ef322369ac6
- 21d ago Changed 521de5f42216
- 25d ago Changed · +2 lines de14ce2127e4
- 26d ago Changed · +2 lines 8a5d63610cd9
- 28d ago First seen · 103 lines · 0 tokens per session scan A b37bf54c6307
animation-editor is a skill published in the GitHub repository vchelaru/FlatRedBall2 (15 stars, last pushed today), licensed MIT. It adds 54 tokens to every session and 3,117 once invoked, about $0.0002 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 2026-09-04.
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