Prototype

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

Pick a branch

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

• "Does this logic / state model feel right?" → 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. 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 — 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

1. Throwaway from day one, and clearly marked as such. Locate the prototype code close to where it will actually be used (next to the module or page it's prototyping for) so context is obvious — but name it so a casual reader can see it's a prototype, not production. For throwaway UI routes, obey whatever routing convention the project already uses; don't invent a new top-level structure.
2. Trivial to run. A UI prototype starts from one command in the project's task runner — pnpm <name>, python <path>, bun <path>, etc. A logic demo is a single HTML file the user double-clicks. Either way, no thinking required to start it.
3. No persistence by default. State lives in memory. Persistence is the thing the prototype is checking, not something it should depend on. If the question explicitly involves a database, hit a scratch DB or a local file with a clear "PROTOTYPE — wipe me" name.
4. Skip the polish. No tests, no error handling beyond what makes the prototype runnable, no abstractions. The point is to learn something fast.
5. Surface the state. After every action (logic) or on every variant switch (UI), print or render the full relevant state so the user can see what changed.
6. Capture it when done. Fold any validated decision into the real code, then capture the prototype itself as a primary source: commit it to a throwaway branch, out of main. Record the answer — the verdict and the question it settled — in whatever planning artifact drove the prototype: the wayfinder ticket's Resolution, the openspec change dir's design doc, or the .scratch notes for the effort, with a pointer to the throwaway branch. The main branch keeps only the validated decision.

踩過的坑

• 2026-08-11 吸收上游 6bcbcb0：logic 分支載具從 terminal app 換成單檔 HTML（free-play 按鈕＋tabbed guided walkthrough、非開發者可自行操作），rule 2「One command to run」放寬為「Trivial to run」；LOGIC.md 整檔換上游版（本地原為 pin 原樣、無自訂要保）、description 同步；pin 推進 6bcbcb0。
• 2026-08-02 fork 自 mattpocock/skills 697d4ce。改動僅 rule 6 capture 落點：上游寫回 issue tracker 的 implementation issue，本 fork 改寫回本地規劃 artifact（wayfinder 票 / openspec change dir / .scratch）；LOGIC.md、UI.md 原樣保留。上游 agents/openai.yaml（Codex runtime 介面宣告）不引入。
• 既有簡易 mockup 慣行（含 codex mockup）只覆蓋 UI 分支的單變體版——本 skill 的增量是 logic 分支單檔 HTML、UI 多變體結構性差異＋URL 切換、surface-the-state、capture 協議。產生變體的載具不限（codex 產 mockup 照用），落地與 capture 照本 skill。