# Implementation Plan: [FEATURE]

**Branch**: `[###-feature-name]` | **Date**: [DATE] | **Spec**: [link]
**Input**: Feature specification from `/specs/[###-feature-name]/spec.md`

**Note**: This template is filled in by the `/speckit.plan` command. See `.specify/templates/commands/plan.md` for the execution workflow.

## Summary

[Extract from feature spec: primary requirement + technical approach from research]

## Technical Context

<!--
  ACTION REQUIRED: Replace the content in this section with the technical details
  for the project. The structure here is presented in advisory capacity to guide
  the iteration process.
-->

**Language/Version**: [e.g., Python 3.11, Swift 5.9, Rust 1.75 or NEEDS CLARIFICATION]  
**Primary Dependencies**: [e.g., FastAPI, UIKit, LLVM or NEEDS CLARIFICATION]  
**Storage**: [if applicable, e.g., PostgreSQL, CoreData, files or N/A]  
**Testing**: [e.g., pytest, XCTest, cargo test or NEEDS CLARIFICATION]  
**Target Platform**: [e.g., Linux server, iOS 15+, WASM or NEEDS CLARIFICATION]
**Project Type**: [single/web/mobile - determines source structure]  
**Performance Goals**: [domain-specific, e.g., 1000 req/s, 10k lines/sec, 60 fps or NEEDS CLARIFICATION]  
**Constraints**: [domain-specific, e.g., <200ms p95, <100MB memory, offline-capable or NEEDS CLARIFICATION]  
**Scale/Scope**: [domain-specific, e.g., 10k users, 1M LOC, 50 screens or NEEDS CLARIFICATION]

## Constitution Check

*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*

### I. Extreme Cost-Efficiency
- [ ] All components have Amazon ASIN or mass-market equivalent documented
- [ ] BOM total cost calculated and minimized
- [ ] At least 2 supplier alternatives identified for critical components
- [ ] No exotic components requiring special supplier relationships

### II. 3D Printing Reproducibility
- [ ] All printable parts fit within 200mm × 200mm × 200mm build volume
- [ ] Support structures do not exceed 30% part volume
- [ ] STL files provided in print-ready orientation
- [ ] Print settings documented (layer height, infill, material)
- [ ] Assembly instructions include photos/diagrams
- [ ] Tolerances account for ±0.2mm print variance
- [ ] Post-processing limited to basic tools (knife, sandpaper, soldering iron)

### III. Lightweight Design
- [ ] Total device weight under 150 grams (excluding measured object)
- [ ] Infill patterns and wall thickness optimized for strength-to-weight ratio
- [ ] Weight distribution documented and optimized
- [ ] Calibration procedure accounts for self-weight offset
- [ ] Scale/sensor placement minimizes impact on small surfaces

### IV. Software Simplicity (Plug-and-Play)
- [ ] No app store submission or account creation required
- [ ] No cloud services or internet required for core functionality
- [ ] Firmware supports direct USB programming (no proprietary tools)
- [ ] Data output uses standard protocols (USB serial, CSV, simple HTTP)
- [ ] Configuration via plain text files or physical controls
- [ ] Libraries use permissive licenses (MIT, Apache 2.0, BSD)
- [ ] Setup procedure does not exceed 3 steps

### Hardware Design Requirements
- [ ] Component specifications documented (voltage, current, protocol)
- [ ] Component availability verified in US, EU, Asia markets
- [ ] Fasteners use metric sizes (M2, M3, M4) from assortment kits
- [ ] Soldering limited to through-hole (SMD only if unavoidable)
- [ ] Cable lengths and connector types specified in BOM
- [ ] Assembly time under 4 hours for experienced maker
- [ ] Calibration procedure uses household reference objects
- [ ] Measurement accuracy and precision documented
- [ ] Troubleshooting guide for common assembly errors included
- [ ] Tested with at least 3 different 3D printer brands/models

### Software Development Requirements
- [ ] Targets widely-available microcontroller (ESP32, Arduino, RP2040)
- [ ] Uses Arduino framework or PlatformIO
- [ ] Pre-compiled binary included for non-developers
- [ ] Flashing procedure documented for Windows, macOS, Linux
- [ ] Descriptive variable names and comments for non-obvious logic
- [ ] No platform-specific extensions that limit portability
- [ ] Firmware size under 80% of flash capacity
- [ ] Sensor input validation and error handling implemented
- [ ] Serial output in human-readable format (CSV or JSON lines)
- [ ] Baud rate and data format documented
- [ ] Example code provided (Python/JavaScript)
- [ ] Optional web interface has no external dependencies or build steps

## Project Structure

### Documentation (this feature)

```text
specs/[###-feature]/
├── plan.md              # This file (/speckit.plan command output)
├── research.md          # Phase 0 output (/speckit.plan command)
├── data-model.md        # Phase 1 output (/speckit.plan command)
├── quickstart.md        # Phase 1 output (/speckit.plan command)
├── contracts/           # Phase 1 output (/speckit.plan command)
└── tasks.md             # Phase 2 output (/speckit.tasks command - NOT created by /speckit.plan)
```

### Source Code (repository root)
<!--
  ACTION REQUIRED: Replace the placeholder tree below with the concrete layout
  for this feature. Delete unused options and expand the chosen structure with
  real paths (e.g., apps/admin, packages/something). The delivered plan must
  not include Option labels.
-->

```text
# [REMOVE IF UNUSED] Option 1: Single project (DEFAULT)
src/
├── models/
├── services/
├── cli/
└── lib/

tests/
├── contract/
├── integration/
└── unit/

# [REMOVE IF UNUSED] Option 2: Web application (when "frontend" + "backend" detected)
backend/
├── src/
│   ├── models/
│   ├── services/
│   └── api/
└── tests/

frontend/
├── src/
│   ├── components/
│   ├── pages/
│   └── services/
└── tests/

# [REMOVE IF UNUSED] Option 3: Mobile + API (when "iOS/Android" detected)
api/
└── [same as backend above]

ios/ or android/
└── [platform-specific structure: feature modules, UI flows, platform tests]
```

**Structure Decision**: [Document the selected structure and reference the real
directories captured above]

## Complexity Tracking

> **Fill ONLY if Constitution Check has violations that must be justified**

| Violation | Why Needed | Simpler Alternative Rejected Because |
|-----------|------------|-------------------------------------|
| [e.g., 4th project] | [current need] | [why 3 projects insufficient] |
| [e.g., Repository pattern] | [specific problem] | [why direct DB access insufficient] |