Brainstorm — Mobile App Concept

This skill writes one file: design/concept.md. It is collaborative — the user does the deciding; this skill structures the conversation and captures decisions.

Purpose / When to Run

Run when:

• The user picked option A or B in /start (no idea, or a fuzzy theme)
• The user typed /brainstorm <hint> directly
• An existing pitch is too vague to drive /map-systems

Do not run when a complete concept already exists at design/concept.md — direct the user to /design-review design/concept.md instead.

Inputs

• Argument: either open (no constraints) or a free-text hint (e.g., "habit tracker", "audio for runners")
• .claude/docs/technical-preferences.md — to detect platform constraints if pinned
• Optional: existing design/concept.md (if user is iterating on a draft)

Outputs

• design/concept.md — concept document with the eight sections listed in Phase 4
• Optional update to production/session-state/active.md

Phase 1: Parse Argument & Pick Mode

If the argument is open (or empty), run open mode — fully unconstrained, the skill must coax a direction out of the user.

If the argument is anything else, treat it as a hint and run directed mode — the hint becomes the seed, and Phase 2 anchors to it.

If design/concept.md already exists, ask:

• Prompt: "A concept doc already exists. What would you like to do?"
• Options: Iterate on it, Start fresh (back it up first), Cancel

If iterating: read the existing file and treat it as the working draft. Phase 2 questions become "do these still hold?" rather than "what should this be?"

Phase 2: Surface the User's Real Want

Mobile apps live or die on whether they solve a job a real user has on a real day. Spend this phase narrowing to that — do not dive into screens, framework, or monetization yet.

Ask the user, conversationally, three things in sequence (one question at a time, free-text answers — these are not multiple choice):

1. Who is the user? Get specific. Not "people who like fitness" — "intermediate boulderers who train 3x a week and forget to log their attempts."
2. What job do they hire the app to do? Frame as JTBD — "When I'm at the gym, I want to log a project attempt without breaking flow, so I can see my session over time."
3. Where does this happen today? Notes app, spreadsheet, memory, a competing app — the answer reveals the alternative they would defect from.

Reflect each answer back in one sentence to confirm.

If the user is in open mode and stalls, offer 3-5 seed prompts as AskUserQuestion options to break the freeze:

• "Who do you find yourself talking to often whose problem is unsolved?"
• "What did you wish existed last week?"
• "What is the most boring repetitive task on your phone?"
• "What is your hobby's worst pain point?"
• "What do you keep losing track of?"

Phase 3: Sharpen the Concept

Once the JTBD is on the table, work through the remaining shape. Use AskUserQuestion widgets where there are 2-4 clean choices; use free text for open ones.

3a: One-liner

Draft a one-line pitch in the format: [App name TBD] is a [category] for [user] that [verb] [object] so they can [outcome].

Show it. Use AskUserQuestion:

• Prompt: "Does this one-liner capture it?"
• Options: Yes, Tighten the verb, Wrong category, Wrong outcome, Rewrite — I'll dictate

Iterate until approved.

3b: Primary platform

Use AskUserQuestion:

• Prompt: "Which platform first?"
• Options:
  • iOS first — App Store, iOS HIG, Swift / SwiftUI native
  • Android first — Play Store, Material 3, Kotlin / Compose native
  • Cross-platform from day one — React Native or Flutter
  • Decide later in /setup-framework

Record their pick. Note this is a recommendation — /setup-framework finalizes it.

3c: Primary success metric

Every app needs one number that proves it works. Ask:

• Prompt: "What single metric tells you it is working?"
• Options:
  • D7 retention — does the user come back a week later
  • Sessions per week — engagement frequency
  • Task completion rate — percentage of users who finish the core flow
  • Session length — depth per session
  • Conversion to paid — for monetized apps
  • Custom — describe it (free text)

This becomes the North Star metric in the concept doc.

3d: MVP scope (the cuts)

Mobile MVP scope is about what to remove, not what to add. Ask:

• "If you only shipped one screen and one core flow, what is it?" (free text)
• "What are 3-5 features you would cut from v1 even though they are tempting?" (free text, list)

The cut list is more useful than the keep list — capture both verbatim.

3e: Anti-pitch (what this is NOT)

To prevent feature creep:

• "What does this app explicitly not do? What are nearby competitors doing that you will refuse to copy?" (free text)

3f: Visual & tone anchor

Even before /design-bible, capture a feeling:

• Prompt: "Pick a tone direction:"
• Options:
  • Calm and minimal (Bear, Things, iA Writer)
  • Playful and bold (Duolingo, Headspace)
  • Dense and powerful (Bloomberg, Pro Camera apps)
  • Warm and personal (Day One, Cozy)
  • Other — describe in free text

Capture 1-3 reference apps the user admires for visuals. These get re-read by /design-bible.

3g: Monetization stance (early signal)

Just a stance, not a plan:

• Options: Free, Free + IAP, Free trial → subscription, One-time paid, Ads, Undecided

3h: Riskiest assumption

Ask: "What is the single belief that, if wrong, kills the idea?" — this becomes the prototype target.

Phase 4: Write the Concept Doc

Use Write to create design/concept.md with these sections, filled from the conversation:

# [App Name] — Concept

> **Status**: Draft
> **Last Updated**: [today]

## 1. One-liner
[the approved sentence from 3a]

## 2. Target User
- Primary persona: [from 2.1]
- Daily context: [from 2.3]
- Job-to-be-done: [from 2.2]

## 3. Core Promise
[what the app fundamentally promises in one paragraph]

## 4. MVP Scope
**In v1:**
- [single core flow]
- [supporting screens]

**Cut from v1 (deliberate):**
- [list]

**Anti-features (will not build):**
- [list]

## 5. Primary Metric
[the chosen North Star + the rough target if user offered one]

## 6. Tone & Visual Anchor
- Tone: [from 3f]
- Reference apps: [list]
- One-word feeling: [extract from 3f]

## 7. Monetization Stance
[from 3g — note "to be confirmed in monetization PRD"]

## 8. Riskiest Assumption
[from 3h — flag as the target for `/prototype`]

## 9. Open Questions
- [anything raised during brainstorm that did not resolve]

Before writing, ask: "May I write this to design/concept.md?"

Phase 5: Hand Off

After the file is written:

1. Update production/session-state/active.md:
   • Task: "Concept brainstormed for [app name]"
   • Files: design/concept.md
   • Next: /setup-framework if framework is unset
2. Use AskUserQuestion:
   • Prompt: "What's next?"
   • Options:
     • Run /setup-framework — pin the framework
     • Run /design-review design/concept.md — independent review
     • Run /design-bible — visual identity (after framework)
     • Stop here for now
3. Suggest opening a fresh session for /design-review so the reviewer is independent.

Examples

Hint: bouldering project tracker

• Phase 2 produces: persona = "intermediate boulderers V4-V7", JTBD = "log attempts on the wall mid-session", today = "memory + paper".
• One-liner: "Sendr is a project tracker for intermediate boulderers that captures wall attempts in two taps so they can see progression across months."
• Platform: iOS first.
• Metric: D30 retention.
• MVP cut list: social feed, video upload, gym map.
• Riskiest assumption: "people will tap during a session instead of after."

Collaborative Protocol

• Question → Options → Decision → Draft → Approval before any file write
• Reflect every answer back in one sentence — do not collect silently
• If the user contradicts an earlier answer, pause and reconcile rather than overwriting
• Never invent a persona, metric, or feature the user did not say or confirm