Getting it into your agent
This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.
/plugin marketplace add AlterLab-IEU/AlterLab_GameForge/plugin install gameforgeWrote 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/alterlab-ieu/alterlab_gameforge/game-prototype)<a href="https://agentmods.dev/skills/alterlab-ieu/alterlab_gameforge/game-prototype"><img src="https://agentmods.dev/badge/skills/alterlab-ieu/alterlab_gameforge/game-prototype/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/alterlab-ieu/alterlab_gameforge/game-prototype"><img src="https://agentmods.dev/badge/skills/alterlab-ieu/alterlab_gameforge/game-prototype.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 | $0.00087 | $0.04582 |
| Opus 5.5 | $0.00035 | $0.01833 |
| Sonnet 5.5 | $0.00017 | $0.00916 |
| Haiku 4.5 | $0.00009 | $0.00458 |
Grade A, and why
game-prototype 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 today.
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 — 327 lines — stays where its author put it; the contents beside it link to each section on GitHub.
AlterLab GameForge -- Hypothesis-Driven Prototyping
A prototype is an experiment, not a demo. Every prototype exists to answer one question, usually "is this worth building?", and the moment you start polishing it you have stopped prototyping and started building, possibly the wrong thing. This workflow enforces the discipline: name the question, write a hypothesis that can fail, build the cheapest thing that tests it, watch real players, and make a binary kill-or-promote call on the evidence.
Coding agents changed the cost of the build step, not the discipline. An agent can produce a playable throwaway in an hour, which makes it tempting to skip the question and "just build it." Cheap builds make a clear question more important, not less: without one you get ten prototypes and no answers.
Continuity through files. Read .gameforge/project.json (pillars, phase), design/concept.md,
earlier reports in design/prototypes/, and production/session-state/active.md. Each prototype
lives in prototypes/<name>/ with a QUESTION.md; the report goes to
design/prototypes/<name>-report.md; active.md gets the decision and the next step. If the
project's phase is still concept or pre-production, offer to set it to prototype.
When NOT to use me
| The user wants... | Route to |
|---|---|
| A small, complete, shippable game (web or jam) built with an agent | /gameforge:game-vibe-code |
| A jam entry with a deadline | /gameforge:game-jam-mode |
| An idea to prototype in the first place | /gameforge:game-brainstorm |
| A vertical slice to show investors or a publisher | That is a demo; plan it with /gameforge:game-producer |
| Tuning numbers in a mechanic already proven fun | /gameforge:game-balance-check |
| A structured playtest of a real build with many players | /gameforge:game-playtest |
| Content questions ("do players like this art style?") | /gameforge:game-playtest or /gameforge:game-art-director |
Critical Rules
- One question per prototype. Two questions means two prototypes. Combined questions contaminate results: when it fails, you will not know which part failed.
- Time-box it. Hours for paper and agent-built throwaways, one to three days at most for anything else. If the question cannot be answered inside the box, decompose it.
- Prototype code does not graduate. When the hypothesis is confirmed, production starts from a spec, not from the prototype. This is cheaper than ever with agents: hand the agent the report and let it build clean. Celeste is a well-documented example: Celeste Classic was a PICO-8 game made in four days for a 2015 jam; the 2018 game was a separate C# build.
- Ugly is correct. Rectangles, primitives, placeholder sounds. AI-generated placeholders are fine if they are logged and never ship by accident (see AI placeholder assets below).
- Observe behavior, not opinions. What players do outranks what they say.
- Kill without sentiment. Clever, beloved, expensive: irrelevant if the evidence says no.
- Original designs only. Prototype genre mechanics and your own ideas, not a recreation of a specific existing game; Claude Code declines those, and they teach you nothing about your game.
- Use the shared theory. MDA, Flow and Self-Determination Theory are in
${CLAUDE_PLUGIN_ROOT}/docs/game-design-theory.md.
What ships with it
2 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.
- today Changed · +16 lines · -10 tokens per session 06133797c8f5
- 2mo ago First seen · 311 lines · 97 tokens per session scan A dc1b63c7fa74
game-prototype is a skill published in the GitHub repository AlterLab-IEU/AlterLab_GameForge (52 stars, last pushed yesterday), licensed MIT. It adds 87 tokens to every session and 4,582 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 2026-08-30.
game-prototype compared with skills from other repositories
| Mod | Type | Stars | Last push | Licence | Scan | Tokens | Works with |
|---|---|---|---|---|---|---|---|
| game-prototypeAlterLab-IEU/AlterLab_GameForge | Skill | 52 | yesterday | MIT | A | 87 | Claude Code |
| playtest-reportDonchitos/Claude-Code-Game-Studios | Skill | 36k | 18d ago | MIT | A | 20 | Claude Code |
| godot-signals-groupsgamedev-skills/awesome-gamedev-agent-skills | Skill | 6.9k | 9d ago | Apache-2.0 | A | 95 | Claude Code |
| scenario-unreal-gameplayscenario-labs/skills | Skill | 3.2k | yesterday | MIT | A | 121 | Claude Code |
| motionOpenDCAI/GameFactory-3A | Skill | 1.0k | 8d ago | Apache-2.0 | A | 0 | Claude Code, Codex |
| unity-addressablesBesty0728/Unity-Skills | Skill | 1.9k | yesterday | MIT | A | 25 | Claude Code, Codex |
| unity-manual-componentBesty0728/Unity-Skills | Skill | 1.9k | yesterday | MIT | A | 36 | Claude Code, Codex |