# Toy

> Use when the user wants to understand a system by interacting with it themselves — asks for a debugger, visualizer, simulator, stepper, playground, or command center as an aid to their own understanding — or when reading and explanation haven't built intuition for how something behaves. Not for user-facing product features (a docs playground, a UI component, a customer demo).

- Skill: `majiayu000/toy` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add majiayu000/toy`
- Raw SKILL.md: https://api.skillmd.com/api/skills/majiayu000/toy/raw
- Safety review: pending (external: skill-scanner PASS, skillspector PASS)
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Web & Frontend
- Author: majiayu000 (https://skillmd.com/u/majiayu000)
- Updated: 2026-09-09
- Page: https://skillmd.com/skills/majiayu000/toy

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# toy

To learn French, live in France. Build the smallest world the human can inhabit to intuit how the system works.

## Rules

- **The human drives; the world shows.** Never automate the step they're trying to learn — build the control panel, let them press run.
- **State visible, time scrubbable.** Surface the hidden things: the stack, the queue, the coordinates, the intermediate value. Step forward, step back, scrub.
- **Consequences immediate.** Every action re-renders its effect next to its cause.
- **Real system when cheap, toy data when the real thing is heavy.**
- **Disposable by default.** Outside the repo, filename prefixed `YYYY-MM-DD-`. A world earns a commit only when it gets reused.

## What they're grasping → world shape

| Understanding sought | Build |
| --- | --- |
| Execution / runtime behavior | Stepper: scrub through time, internals visible at each step |
| A migration, port, or bulk change | Command center: human triggers each step, before/after side by side |
| A data structure or algorithm | Manipulable objects with live values |
| A parameter or design space | Sliders with instant re-render |

Let the human pin notes to the step or state on screen — understanding sticks to the moment it happened.