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 ericrisco/rsc-harness --skill gamedev-physicsgit clone --depth 1 https://github.com/ericrisco/rsc-harnessWrote 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/ericrisco/rsc-harness/gamedev-physics)<a href="https://agentmods.dev/skills/ericrisco/rsc-harness/gamedev-physics"><img src="https://agentmods.dev/badge/skills/ericrisco/rsc-harness/gamedev-physics/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/ericrisco/rsc-harness/gamedev-physics"><img src="https://agentmods.dev/badge/skills/ericrisco/rsc-harness/gamedev-physics.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 | $0.00102 | $0.03739 |
| Opus 5.5 | $0.00041 | $0.01496 |
| Sonnet 5.5 | $0.00020 | $0.00748 |
| Haiku 4.5 | $0.00010 | $0.00374 |
Grade A, and why
gamedev-physics 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 1mo 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 — 226 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Game physics & collision
Make bodies collide, move, and stay stable across Godot, Unity, and Unreal. This skill owns the mental model (body types, colliders, layers/masks, character controllers, joints, queries, determinism) and maps every concept onto each engine's real API. When physics "feels broken" — jitter, tunneling, sinking, ghost collisions — the cause is almost always one of: wrong body type, a layer/mask mismatch, or moving/integrating outside the fixed physics tick. Check those first.
Version contract — read first (never emit these)
| Engine | Target | Banned / deprecated | Use instead |
|---|---|---|---|
| Godot | 4.x | move_and_slide(velocity, up, ...) with arguments (that is Godot 3) |
Godot 4 move_and_slide() takes no args; set the velocity property first |
| Godot | 4.x | KinematicBody2D/3D, RayShape, WorldMarginShape, linear_velocity *= delta before move_and_slide() |
CharacterBody2D/3D, SeparationRayShape2D/3D, WorldBoundaryShape2D/3D; move_and_slide() is already delta-scaled |
| Unity | Unity 6 (6000.x) | Rigidbody.velocity / Rigidbody2D.velocity, rb.drag, rb.angularDrag |
linearVelocity (+ linearVelocityX/Y), linearDamping, angularDamping; new AddForceX/Y |
| Unity | Unity 6 | moving a dynamic Rigidbody from Update; transform.position = on a physics body |
move in FixedUpdate; use MovePosition/AddForce, never write transform on a simulated body |
| Unreal | UE5 (Chaos) | any PhysX/APEX API, bUseAsyncScene, NvCloth |
Chaos is the only physics backend in UE5; use UPrimitiveComponent physics + PhysicsConstraintComponent |
If you are unsure a symbol exists in the user's exact version, say so instead of inventing it.
When to use / When NOT to use
Use when: designing which body type a thing should be; something falls through, sinks into, or passes through geometry; a rigid body jitters, drifts, or launches; setting up collision layers/masks/channels; building or fixing a character/player controller; adding joints; casting rays/shapes or overlap tests; or physics behaves differently at different frame rates.
What ships with it
5 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.
- 1mo ago First seen · 226 lines · 102 tokens per session scan A 85164aabe41f
gamedev-physics is a skill published in the GitHub repository ericrisco/rsc-harness (267 stars, last pushed 2d ago), licensed MIT. It adds 102 tokens to every session and 3,739 once invoked, about $0.0004 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 2026-09-03.
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