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.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/instructions/vchelaru/flatredball2/claude-md)<a href="https://agentmods.dev/instructions/vchelaru/flatredball2/claude-md"><img src="https://agentmods.dev/badge/instructions/vchelaru/flatredball2/claude-md/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/instructions/vchelaru/flatredball2/claude-md"><img src="https://agentmods.dev/badge/instructions/vchelaru/flatredball2/claude-md.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 | $0.04591 | $0.04591 |
| Opus 5.5 | $0.01836 | $0.01836 |
| Sonnet 5.5 | $0.00918 | $0.00918 |
| Haiku 4.5 | $0.00459 | $0.00459 |
Grade A, and why
FlatRedBall2 CLAUDE.md 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 6d 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 — 225 lines — stays where its author put it; the contents beside it link to each section on GitHub.
@design/TODOS.md
Repository Guidelines
What Is This?
FlatRedBall2 is a 2D game engine/framework written in C# on .NET, built on top of MonoGame. It integrates Gum (UI) and Tiled (level editing) as dependencies.
Prerelease Status — Breaking Changes Are Free
FlatRedBall2 is in active prerelease development. There are no shipping consumers, no public API surface to preserve, and no backwards-compatibility obligations. Anything in the engine — type names, method signatures, namespaces, defaults, semantics — can be changed at any time if a better design exists.
When proposing or evaluating a change:
- Do not raise "this will break existing code" as a concern. It is not a concern. Existing call sites in samples and tests are part of this codebase and will be updated alongside the change.
- Do not add deprecation shims,
[Obsolete]attributes, alias members, or "kept for compatibility" wrappers. Just change the thing. - Do propose the cleanest API; if a rename or restructuring makes the engine clearer, it is on the table.
The only relevant question is "is this the right design?" — never "will this break someone?"
Exception: the .achx/.achj file formats are not FRB2-owned. They are shared with Gum and FRB1 and have consumers with years of existing files. AnimationChainListSave must keep reading and writing them byte-compatible: element/array schema, chain order, and duplicate chain names all preserved on a load→save round-trip.
Key Files
- Main project:
src/FlatRedBall2.csproj(KNI;nkast.Xna.Framework*versions pinned in the rootDirectory.Packages.props) - Code style:
.claude/code-style.md - Deferred items:
design/TODOS.md - Sample catalog, by skill (with gaps):
design/SAMPLES.md - Multi-phase plans:
plan/plan.md(index) — see below - Test project:
tests/FlatRedBall2.Tests/FlatRedBall2.Tests.csproj
Multi-Phase Plans (plan/)
Create a plan only when the user explicitly asks for one. Start work on <issue> means implement, test, push, and open a PR; do not stop at a plan or plan-only commit.
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.
- 6d ago Changed · -3 tokens per session e544675fe6ef
- 10d ago Changed · +84 tokens per session 2e2c0f56a6e5
- 12d ago Changed · -8 tokens per session 4960d6ac9630
- 18d ago Changed · +1 lines · +92 tokens per session 535076a16412
- 28d ago Changed · +1 lines · +22 tokens per session ca5a78f19d5e
- 1mo ago Changed · +1 lines · +21 tokens per session 024b8192565b
- 1mo ago Changed · +2 lines · +117 tokens per session 4234ae567098
- 1mo ago Changed · +17 lines · +434 tokens per session 7387ad9a29a1
- 1mo ago Changed · +2 lines · +78 tokens per session 8e92bbb4ad09
- 1mo ago First seen · 201 lines · 3,754 tokens per session scan A 7ddab5f92fba
FlatRedBall2 CLAUDE.md is an instructions file published in the GitHub repository vchelaru/FlatRedBall2 (15 stars, last pushed today), licensed MIT. It adds 4,591 tokens to every session, about $0.0184 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.
Other instructions, from other repositories
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.
vscode copilot-instructions.md
Copilot instructions for microsoft/vscode, covering vs code copilot instructions, project overview, root folders, core architecture (src/ folder) and built-in extensions (extensions/ folder).
deno copilot-instructions.md
Copilot instructions for denoland/deno, covering deno development guide for github copilot, network access, high level overview, key directories and key files to understand first.