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 kyu-n/gdx-claude-skills --skill libgdx-box2dgit clone --depth 1 https://github.com/kyu-n/gdx-claude-skillsWrote 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/kyu-n/gdx-claude-skills/libgdx-box2d)<a href="https://agentmods.dev/skills/kyu-n/gdx-claude-skills/libgdx-box2d"><img src="https://agentmods.dev/badge/skills/kyu-n/gdx-claude-skills/libgdx-box2d/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/kyu-n/gdx-claude-skills/libgdx-box2d"><img src="https://agentmods.dev/badge/skills/kyu-n/gdx-claude-skills/libgdx-box2d.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 | $0.00128 | $0.03391 |
| Opus 5 | $0.00064 | $0.01695 |
| Sonnet 5 | $0.00026 | $0.00678 |
| Haiku 4.5 | $0.00013 | $0.00339 |
Grade A, and why
libgdx-box2d 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 12d 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 — 280 lines — stays where its author put it; the contents beside it link to each section on GitHub.
libGDX Box2D Physics
Quick reference for the libGDX Box2D JNI wrapper (com.badlogic.gdx.physics.box2d.*). Covers World, Body, Fixture, Shape, filtering, contacts, joints, debug rendering, and the PPM pattern.
Units — Box2D Works in Meters
Box2D is tuned for objects 0.1–10 meters. Using pixel coordinates causes sluggish movement (internal velocity cap is 2 units/timestep).
Approach 1 — PPM constant:
public static final float PPM = 100f; // 100 pixels = 1 meter
// Creating bodies: bodyDef.position.set(pixelX / PPM, pixelY / PPM);
// Rendering sprites: sprite.setPosition(body.getPosition().x * PPM, body.getPosition().y * PPM);
// Debug renderer: debugRenderer.render(world, camera.combined.cpy().scl(PPM));
Approach 2 — Camera in meters (cleaner):
camera = new OrthographicCamera();
camera.setToOrtho(false, viewportWidthMeters, viewportHeightMeters);
// All game logic in meters. Debug renderer uses camera.combined directly.
debugRenderer.render(world, camera.combined);
World
World world = new World(new Vector2(0, -10f), true); // gravity, doSleep
Fixed timestep — the accumulator pattern (REQUIRED):
private static final float TIME_STEP = 1 / 60f;
private static final int VELOCITY_ITERATIONS = 6;
private static final int POSITION_ITERATIONS = 2;
private float accumulator = 0;
private void stepPhysics(float deltaTime) {
float frameTime = Math.min(deltaTime, 0.25f); // cap to prevent spiral of death
accumulator += frameTime;
while (accumulator >= TIME_STEP) {
world.step(TIME_STEP, VELOCITY_ITERATIONS, POSITION_ITERATIONS);
accumulator -= TIME_STEP;
}
}
DO NOT pass Gdx.graphics.getDeltaTime() directly to world.step() — variable timestep causes tunneling and non-deterministic behavior.
Key methods:
world.setContactListener(listener); // ContactListener
world.setContactFilter(filter); // ContactFilter — boolean shouldCollide(Fixture, Fixture)
world.setGravity(new Vector2(0, -10f));
world.getGravity(); // returns REUSED Vector2 — copy if storing
world.isLocked(); // true during step — cannot modify world
// Queries — coordinates in meters (world units)
world.QueryAABB(callback, lowerX, lowerY, upperX, upperY); // note: capital Q
world.rayCast(callback, point1, point2); // Vector2 or float overloads
// Bulk retrieval — clears array first, then populates
Array<Body> bodies = new Array<>();
world.getBodies(bodies); // NOT a return-value method
world.dispose(); // MUST call when done
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.
- 12d ago First seen · 280 lines · 128 tokens per session scan A b78ffa25ccf4
libgdx-box2d is a skill published in the GitHub repository kyu-n/gdx-claude-skills (4 stars, last pushed 7mo ago), licensed MIT. It adds 128 tokens to every session and 3,391 once invoked, about $0.0006 per session on Opus 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 2026-08-31.
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