game-prototype

A hypothesis-driven way to test a game idea by building the smallest experiment that can answer one important question. A prototype is treated as a test, not as a polished demo.

In plain words
What is it for?
Testing mechanics, validating assumptions with players, comparing competing designs, and deciding whether an idea should be developed further.
Why use it?
It helps teams learn whether a mechanic is worth building before spending time on full production or polish.

Skill for Claude CodeCodex

Install

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.

agentmods
npx agentmods add skills/alterlab-ieu/alterlab_gameforge/game-prototype
Any agent
npx skills add AlterLab-IEU/AlterLab_GameForge --skill game-prototype
Clone the repo
git clone --depth 1 https://github.com/AlterLab-IEU/AlterLab_GameForge

Made for: Claude Code, Codex.

Per session 97 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 5,169 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5 $0.00097 $0.05169
Opus 5 $0.00048 $0.02584
Sonnet 5 $0.00019 $0.01034
Haiku 4.5 $0.00010 $0.00517

Measured 2d ago against content hash dc1b63c7fa74, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

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 2d 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.

skills/workflows/game-prototype/SKILL.md · 311 lines

How it starts

The opening of the file, as written. The whole thing — 311 lines — stays where its author put it; the contents beside it link to each section on GitHub.

AlterLab GameForge -- Hypothesis-Driven Prototyping

Prototypes are experiments, not demos. Every prototype exists to answer one question: "Is this worth building?" The moment you start polishing a prototype, you have stopped prototyping and started building -- and you may be building the wrong thing. Undertale's original demo was rough, ugly, and proved exactly one thing: the bullet-hell-meets-RPG mechanic was worth a full game. Hollow Knight started as a game jam prototype that validated tight combat in an atmospheric 2D world. Celeste began as a PICO-8 prototype that proved a single idea: precise air-dash platforming feels incredible at 8x8 pixel resolution. This workflow enforces that same discipline: define a hypothesis, build the minimum viable test, observe real players, make a binary kill-or-promote decision based on evidence.

Purpose & Triggers

Invoke this workflow when:

  • A team member proposes a new mechanic and the response should be "prove it" rather than "ship it"
  • The design document contains an assumption that has never been tested with real players
  • Two competing mechanic designs need a head-to-head bake-off to determine which one feels better
  • A feature sounds good on paper but the team has no visceral sense of whether it will be fun
  • Pre-production needs to validate core loops before committing engineering resources
  • A pivot is being considered and the new direction needs rapid feasibility confirmation

Do NOT use this workflow when:

  • The mechanic is well-understood and already validated in similar games (just build it properly)
  • You need a vertical slice for stakeholder presentation (that is a demo, not a prototype)
  • The question is about content, not mechanics (content questions need playtesting, not prototyping)

Critical Rules

  1. One hypothesis per prototype. If you are testing two things, you have two prototypes. Combining hypotheses contaminates your results -- when it fails, you will not know which part failed.
  2. Time-box or die. Every prototype gets a strict time limit: 1-3 days maximum. If the hypothesis cannot be tested in that window, the scope is too large. Decompose it further.
  3. Prototype code is biohazard. It does not graduate to production. Ever. When a hypothesis is validated, the real implementation starts from scratch with proper architecture. Letting prototype code leak into production is how technical debt is born. Celeste's PICO-8 prototype shared zero code with the final game -- it proved the feel, then the real build started clean.
  4. Ugly is correct. Colored rectangles for characters. Placeholder sounds. Programmer art. Comic Sans labels. If anyone comments on the visual quality of a prototype, they have misunderstood its purpose. The Hollow Knight game jam prototype used simple silhouettes -- the atmosphere came later, the feel came first.
  5. Observe behavior, not opinions. Players will tell you what they think you want to hear. Watch what they DO. A player who says "yeah it was fine" but leaned forward and played for 20 minutes straight is giving you different data than their words suggest.
  6. Kill without sentiment. If the evidence says the hypothesis is false, the prototype dies. It does not matter how clever the idea was, how much you personally like it, or how much time you spent building it. Supergiant kills prototypes constantly -- their GDC talks reveal dozens of dead mechanics that never made it past the test phase because the team trusts evidence over attachment.
  7. Always reference docs/game-design-theory.md for shared theoretical frameworks (MDA, Flow Theory, SDT) when formulating hypotheses about player experience.

Read the full file on GitHub · 311 lines

Changes

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.

  1. 2d ago First seen · 311 lines · 97 tokens per session scan A dc1b63c7fa74

Subscribe to this mod's changes

game-prototype is a skill published in the GitHub repository AlterLab-IEU/AlterLab_GameForge (34 stars, last pushed 5mo ago), licensed MIT. It adds 97 tokens to every session and 5,169 once invoked, about $0.0005 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 2026-08-30.

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