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 game-designgit 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/game-design)<a href="https://agentmods.dev/skills/ericrisco/rsc-harness/game-design"><img src="https://agentmods.dev/badge/skills/ericrisco/rsc-harness/game-design/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/game-design"><img src="https://agentmods.dev/badge/skills/ericrisco/rsc-harness/game-design.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 | $0.00078 | $0.03421 |
| Opus 5.5 | $0.00031 | $0.01368 |
| Sonnet 5.5 | $0.00016 | $0.00684 |
| Haiku 4.5 | $0.00008 | $0.00342 |
Grade A, and why
game-design 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 — 147 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Design games that are fun on purpose
Engine-agnostic game design: mechanics, loops, progression, economy, balance, feel, and the discipline of prototyping and scope. No engine APIs live here — when the design is settled, the implementation belongs to godot, unity, or unreal.
Two premises govern everything below. Fun is discovered, not designed — you cannot reason your way to a fun game on paper, you find it by building the smallest playable version and playing it, so every hour spent planning a mechanic you have not prototyped is an hour spent guessing. And a game is the set of verbs it gives the player plus the loops those verbs live in — art, story, and levels dress that skeleton; if the skeleton is not fun in greybox, nothing dresses it into fun.
Route elsewhere when the ask is not design:
| The ask | Route to | Why not here |
|---|---|---|
| Write the movement/AI/shader/save code | godot / unity / unreal |
This skill decides what to build; the engine skill builds it. |
| Author the story, dialogue, characters, lore | game-storytelling |
Narrative design is its own craft; this skill owns systems and verbs. |
| Lay out a level, encounter, or world map | level-design |
Spatial/encounter design applies the mechanics this skill defines. |
| Netcode, prediction, lag compensation | gamedev-multiplayer |
A technical domain, not core design intent. |
| Ship / store page / build pipeline | gamedev-shipping |
Release logistics, not design. |
Loops: moment-to-moment → session → meta
A game is loops nested inside loops. Each layer must reward on its own and feed motivation to the layer above it.
moment-to-moment (seconds) the primary verb: aim+fire, jump, place, click, parry
│ feeds
session loop (minutes) a run / match / mission: setup → tension → resolution
│ feeds
meta loop (sessions) mastery, unlocks, collection, rank — why you return tomorrow
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 · 147 lines · 78 tokens per session scan A 9ee4a050ada0
game-design is a skill published in the GitHub repository ericrisco/rsc-harness (247 stars, last pushed yesterday), licensed MIT. It adds 78 tokens to every session and 3,421 once invoked, about $0.0003 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.
Other skills, from other repositories
game-designer
For Phaser 4/Three.js on Android/iOS, use Mobile Monetization before generic examples. Own the per-game player/value, monetization and level/economy hypotheses; preserve the free path and approved reference mechanics. Use the existing studio gates and shared profile/game delta; forge mobile doctor reports assumptions…
day-one-patch
Day-one launch patch — focused fix for known issues found after gold master. Mini-sprint with QA gate and rollback.
quick-design
Lightweight spec for small changes — tuning adjustments, minor mechanics. Embeds directly into stories; skips full GDD.
playtest-report
Structured playtest report template, or turn existing playtest notes into structured feedback.
team-polish
Orchestrate the polish team — performance-analyst, technical-artist, sound-designer, qa-tester — to optimize and harden a feature or area.
ux-design
Section-by-section UX spec authoring for a screen, flow or HUD. Reads the player journey to provide context; also project-wide accessibility.