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Agent skill

Prototype Fast

by gamedev-skills in gamedev-skills/awesome-gamedev-agent-skills

Build a playable prototype in about an hour to answer one question — is it fun?

Apache-2.0Auto-check passedDevelopment

Install Prototype Fast

skills CLI
$ npx skills add gamedev-skills/awesome-gamedev-agent-skills --skill prototype-fast -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install gamedev-skills/awesome-gamedev-agent-skills prototype-fast --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/gamedev-skills/awesome-gamedev-agent-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/workflows/prototype-fast .claude/skills/prototype-fast && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
prototype-fast
GitHub stars
1.4k
Token cost
~1.5k tokens
SKILL.md length
577 words
Files
1
Skills in repo
53
Repo updated
First seen
Licence
Apache-2.0

At a glance

Build a playable prototype in about an hour to answer one question — is it fun?

  • Works in 4 steps: The prototype brief (fill this in before… → Greybox the core loop, fake everything… → Kill criteria — make the keep/kill call… → …
  • Prototyping a mechanic
  • SKILL.md covers When to use, Core workflow, Patterns and Pitfalls, plus 2 more sections
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Prototype Fast is an agent skill from gamedev-skills/awesome-gamedev-agent-skills. Build a playable prototype in about an hour to answer one question — is it fun? — with greybox primitives, a hard timebox, and explicit keep/kill criteria. Use when prototyping a mechanic, making a vertical slice or MVP, greyboxing/blockout, or judging throwaway vs keep.

Its SKILL.md is about 1.5k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

It sits in Development, covering Prototyping. The repository describes itself as: 74 game-dev skills for AI coding agents — Godot, Unity, Unreal, Phaser, PixiJS, three.js, Bevy, pygame, LÖVE, Roblox. Portable SKILL.md Agent Skills (the format Anthropic… The licence is Apache-2.0.

When your agent uses it

  • Prototyping a mechanic
  • Making a vertical slice
  • Greyboxing/blockout
  • Judging throwaway vs keep

Example prompts

  • “/prototype-fast”

Workflow steps

4 steps, taken from the step headings in SKILL.md.

  1. The prototype brief (fill this in before coding)
  2. Greybox the core loop, fake everything else (engine-agnostic pseudocode)
  3. Kill criteria — make the keep/kill call observable, not emotional
  4. Containment: keep a spike out of the shipping codebase

What it can do on your machine

Read from SKILL.md and the folder at commit d4b0e35. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md.

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Prototype Fast loads about 1.5k tokens when it runs. Until then it costs about 72 tokens; SKILL.md has 577 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~72
When it runs · the whole SKILL.md, loaded when a task matches
~1.5k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from gamedev-skills/awesome-gamedev-agent-skills at commit d4b0e35, republished under its Apache-2.0 licence (© gamedev-skills). 577 words, ~1,500 tokens.

Download SKILL.mdSave it as .claude/skills/prototype-fast/SKILL.md (or your agent's skills folder).
name
prototype-fast
description
Build a playable prototype in about an hour to answer one question — is it fun? — with greybox primitives, a hard timebox, and explicit keep/kill criteria. Use when prototyping a mechanic, making a vertical slice or MVP, greyboxing/blockout, or judging throwaway vs keep.

Prototype Fast

Get a mechanic into a player's hands fast to learn whether it's worth building. The output of a prototype is a decision (keep / kill / refactor), not a product. Optimize for learning speed, and decide up front whether the code is throwaway or load-bearing.

When to use

  • Use when validating a single mechanic or "what if", building a vertical slice / MVP, greyboxing a level or interaction, or de-risking an idea before committing real time.
  • Use when the user says "just get something playable", "is this fun?", or "rough it in".

When not to use: a timed competition with a deadline and a submission (use game-jam); shipping or updating a real release (use steam-publish / itch-publish); building the production version of a validated feature (use the engine/genre skill directly).

Core workflow

  1. Write the one question. State the single thing the prototype must answer, e.g. "Is grappling-while-falling satisfying to control?" If you have two questions, build two prototypes. A prototype that tests everything tests nothing.
  2. Decide throwaway vs keep — before you write code. Throwaway (a spike): hard-code, no architecture, delete after. Keep: still rough, but folder/names you can grow. Most prototypes should be throwaway; pretending otherwise is how prototypes rot into the shipping codebase.
  3. Set a hard timebox (30-90 min for a mechanic; one sitting for a slice) and a visible timer. The constraint is the point — it forces you to test the core idea, not the trim.
  4. Greybox everything non-essential. Primitives for art (boxes, circles, capsules), built-in fonts, one debug sound or none. Spend zero minutes on anything the question doesn't depend on.
  5. Instrument for the question. Add on-screen debug text / gizmos that show the thing you are judging (speed, distance, timing window). You're measuring, not decorating.
  6. Playtest immediately and honestly. Play it yourself, then hand it to one other person without explaining the controls. Watch where they struggle.
  7. Make the call against your kill criteria (below). Keep → schedule the real build and rewrite, don't promote the spike. Kill → log the lesson and move on. Refactor → narrow the question and spike again.
Show full SKILL.md (229 more words)Show less

Patterns

1. The prototype brief (fill this in before coding)
text
QUESTION:     The one thing this must prove (binary if possible).
CORE VERB:    The single action the player repeats.
THROWAWAY?:   yes -> hard-code freely, delete after.  no -> minimal structure to grow.
TIMEBOX:      e.g. 60 min. Stop when it rings, even if unfinished.
KEEP IF:      observable signal that means "fun / worth building" (see kill criteria).
KILL IF:      observable signal that means "stop".
2. Greybox the core loop, fake everything else (engine-agnostic pseudocode)
text
# Only the CORE VERB is real. Visuals are primitives; systems are stubs.
on update(dt):
    read_input()
    apply_core_mechanic(dt)        # the ONLY thing you're testing — make this feel right
    draw_primitive(player)         # a box. not a sprite. not animated.
    draw_debug_hud(speed, timing)  # show the numbers you're judging
    # enemies, menus, save, audio, art -> stubbed or absent until the verb proves out
3. Kill criteria — make the keep/kill call observable, not emotional
text
KEEP when, with placeholder art:
  - a fresh player does the core verb on purpose within ~30s, unprompted, and
  - you (or they) repeat the loop "one more time" without being asked.
KILL when:
  - the verb only feels good after you explain it, or
  - making it fun needs systems far beyond the prototype's scope, or
  - you're adding art/levels to avoid admitting the verb is flat.
REFACTOR when one variable is clearly off (too slow, window too tight) -> retune, retest.
4. Containment: keep a spike out of the shipping codebase
text
prototypes/<idea-name>/      # separate folder or project, never imported by main game
  - hard-coded values, single file ok, magic numbers welcome
  - committed on a throwaway branch (or not at all)
Rule: a "keep" decision authorizes a REWRITE in the real project, not a copy-paste of the
spike. Prototype code carries prototype assumptions; shipping it ships the assumptions.

Pitfalls

  • Polishing too early. Art, menus, and audio make a flat mechanic look finished and delay the verdict. Greybox until the verb is proven.
  • No kill criteria. Without a written "kill if", every prototype "has potential" and nothing gets cut. Decide the signal before you're attached to the code.
  • Building systems instead of the mechanic. Inventory, save/load, and settings are not the question. Stub them.
  • The spike becomes the product. Throwaway code promoted to production is technical debt with a fun origin story. Rewrite on a keep.
  • Prototyping in the real codebase. It tangles experiments with shipping systems and makes the spike expensive to delete. Use a separate folder/project.
  • Testing only yourself. You know the controls and the intent. One uncoached outside player reveals more in two minutes than an hour of self-play.

References

  • For working under a hard external deadline and submitting, read the game-jam skill.
  • For the engine-specific core loop you'll greybox in, read that engine's skill (godot-gdscript, phaser-core, love2d-core, unity-csharp-scripting, …).
  • game-jam — same scope discipline applied to a timed competition with a submission.
  • Engine cores and genre skills — where a "keep" decision gets rebuilt properly.

© gamedev-skills, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in skills/workflows/prototype-fast of gamedev-skills/awesome-gamedev-agent-skills.

Open the folder on GitHubat commit d4b0e35

Compare with similar skills

Prototype Fast next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Prototype Fast compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Prototype Fast this skillgamedev-skills/awesome-gamedev-agent-skills1.4k—~1.5kAutomated safety check: PassApache-2.0
Native Feel Cross Platform Desktopyetone/native-feel-skill1.9k1 repos~1.5kAutomated safety check: PassMIT
Compound Engineering PrototypeEveryInc/compound-engineering-plugin25k—~1.9kAutomated safety check: PassMIT
Collaborating With CodexGuDaStudio/collaborating-with-codex1321 repos~712Automated safety check: PassMIT
Digikeyaklofas/kicad-happy1.4k1 repos~4.5kAutomated safety check: PassMIT
Collaborating With Antigravityappautomaton/agent-designer1311 repos~2.4kAutomated safety check: PassNone

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Categories

Questions about Prototype Fast

What does Prototype Fast do?

Build a playable prototype in about an hour to answer one question — is it fun? Prototype Fast is an agent skill from gamedev-skills/awesome-gamedev-agent-skills. Build a playable prototype in about an hour to answer one question — is it fun?

When should I use Prototype Fast?

Prototype Fast fits situations like: prototyping a mechanic; making a vertical slice; greyboxing/blockout; judging throwaway vs keep.

How do I install Prototype Fast in Claude Code?

Run `npx skills add gamedev-skills/awesome-gamedev-agent-skills --skill prototype-fast -a claude-code`. Or copy the skill folder (skills/workflows/prototype-fast in gamedev-skills/awesome-gamedev-agent-skills) into .claude/skills/prototype-fast in your project. Claude Code loads it when a task matches its description.

How do I install Prototype Fast in Codex?

Run `npx skills add gamedev-skills/awesome-gamedev-agent-skills --skill prototype-fast -a codex`. Or copy the skill folder (skills/workflows/prototype-fast in gamedev-skills/awesome-gamedev-agent-skills) into .agents/skills/prototype-fast in your project. Codex loads it when a task matches its description.

Can I use Prototype Fast in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add gamedev-skills/awesome-gamedev-agent-skills --skill prototype-fast -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/prototype-fast, .gemini/skills/prototype-fast, .github/skills/prototype-fast and .opencode/skills/prototype-fast in your project.

What does Prototype Fast need to run?

SKILL.md names no scripts, command-line tools or credentials: Prototype Fast is instructions for the agent only.

Does Prototype Fast access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Prototype Fast safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Prototype Fast use?

Prototype Fast is published under the Apache-2.0 licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Prototype Fast use?

About 1.5k tokens (SKILL.md is roughly 6k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Prototype Fast?

Skills that share tags, products or a category with Prototype Fast: Native Feel Cross Platform Desktop (yetone/native-feel-skill, 1.9k stars), Compound Engineering Prototype (EveryInc/compound-engineering-plugin, 25k stars), Collaborating With Codex (GuDaStudio/collaborating-with-codex, 132 stars) and Digikey (aklofas/kicad-happy, 1.4k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Prototype Fast?

gamedev-skills (a GitHub organization) maintains it in gamedev-skills/awesome-gamedev-agent-skills, which has 1,356 GitHub stars. The repository holds 53 skills in this directory. The repository was last updated on September 27, 2026.

Source: gamedev-skills/awesome-gamedev-agent-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.