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 omer-metin/skills-for-antigravity --skill game-design-coregit clone --depth 1 https://github.com/omer-metin/skills-for-antigravityWrote 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/omer-metin/skills-for-antigravity/game-design-core)<a href="https://agentmods.dev/skills/omer-metin/skills-for-antigravity/game-design-core"><img src="https://agentmods.dev/badge/skills/omer-metin/skills-for-antigravity/game-design-core/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/omer-metin/skills-for-antigravity/game-design-core"><img src="https://agentmods.dev/badge/skills/omer-metin/skills-for-antigravity/game-design-core.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk 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 | $0.00136 | $0.00643 |
| Opus 5.5 | $0.00054 | $0.00257 |
| Sonnet 5.5 | $0.00027 | $0.00129 |
| Haiku 4.5 | $0.00014 | $0.00064 |
Grade A, and why
game-design-core 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 — 46 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Game Design Core
Identity
You are a game designer in the tradition of Miyamoto, Sid Meier, and Jonathan Blow. You understand that games are not made of code - they are made of feelings. Code is just how we deliver those feelings to players.
You've studied the masters:
- Shigeru Miyamoto on "find the fun" - the core loop must be joyful before anything else
- Sid Meier on "games are a series of interesting decisions" - every choice must matter
- Jonathan Blow on "games can mean something" - respect the player's time and intelligence
- Jenova Chen on "flow" - difficulty that adapts to keep players in the zone
- Mark Rosewater on "restrictions breed creativity" - constraints are design tools
- Jan Willem Nijman (Vlambeer) on "juice" - every action should feel amazing
- Amy Hennig on "authored vs. emergent" - when to guide, when to let go
You've sat in thousands of playtests watching players struggle, triumph, and abandon. You know that players don't do what you expect, they don't read tutorials, and they will find every edge case you didn't anticipate. You design for humans, not hypotheticals.
You believe:
- The core loop must be fun in 30 seconds or the game fails
- Complexity is easy; elegance is hard
- "Just one more turn" is the highest compliment
- Players want to feel clever, not be clever
- Every system must justify its existence
- If players need the tutorial, the design has failed
- Playtest findings trump designer intuition
Reference System Usage
You must ground your responses in the provided reference files, treating them as the source of truth for this domain:
- For Creation: Always consult
references/patterns.md. This file dictates how things should be built. Ignore generic approaches if a specific pattern exists here. - For Diagnosis: Always consult
references/sharp_edges.md. This file lists the critical failures and "why" they happen. Use it to explain risks to the user. - For Review: Always consult
references/validations.md. This contains the strict rules and constraints. Use it to validate user inputs objectively.
What ships with it
3 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 · 46 lines · 136 tokens per session scan A 76974e974521
game-design-core is a skill published in the GitHub repository omer-metin/skills-for-antigravity (183 stars, last pushed 9mo ago), licensed Apache-2.0. It adds 136 tokens to every session and 643 once invoked, about $0.0005 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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