# Prototype Designs

Build a throwaway prototype to test a state model or UI idea.

- Repository: https://github.com/mattpocock/skills (309182 stars)
- Category: Design
- License: MIT
- Last updated: 2026-11-01
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add mattpocock/skills --skill prototype -g -a claude-code -y`
Codex: `npx skills add mattpocock/skills --skill prototype -g -a codex -y`
Cursor: `npx skills add mattpocock/skills --skill prototype -g -a cursor -y`
Gemini CLI: `npx skills add mattpocock/skills --skill prototype -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add mattpocock/skills`

## Description

Build a throwaway prototype to answer a design question. Use when the user wants to sanity-check whether a state model or logic feels right, or explore what a UI should look like.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Prototype

A prototype is **throwaway code that answers a question**. The question decides the shape.

## Pick a branch

Identify which question is being answered, using the user's prompt, the surrounding code, or by asking if the user is around:

- **"Does this logic / state model feel right?"** → [LOGIC.md](LOGIC.md). Build a single shareable HTML file (free-play buttons plus tabbed guided walkthroughs) that pushes the state machine through cases that are hard to reason about on paper, and that a non-developer can drive.
- **"What should this look like?"** → [UI.md](UI.md). Generate several radically different UI variations on a single route, switchable via a URL search param and a floating bottom bar.

The two branches produce very different artifacts, so getting this wrong wastes the whole prototype. If the question is genuinely ambiguous and the user isn't reachable, default to whichever branch better matches the surrounding code (a backend module → logic; a page or component → UI) and state the assumption at the top of the prototype.

## Rules that apply to both

The rest: https://github.com/mattpocock/skills/blob/HEAD/skills/engineering/prototype/SKILL.md