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Idea Stage Draft v1.0

Vellum: Context Overlay

A desktop utility that pins transparent, click-through reference overlays (images, PDFs, websites) on top of your active workspace.

PRODUCT REQUIREMENT DOCUMENT (PRD)

1. Title & One-Liner

Vellum: The Ghost Mode for Your Workflow.

A desktop utility that pins transparent, click-through reference overlays (images, PDFs, websites) on top of your active workspace, eliminating the “Alt-Tab tax” for developers and designers.

2. Platform Target

  • Desktop Only: macOS (Universal), Windows 11/10, Linux (X11/Wayland experimental).

Justification: Requires OS-level window compositing (click-through transparency) not possible in web browsers.

3. Core User Loop

  1. Snap: User selects a region of a screen (or file) to “pin”.
  2. Ghost: The selection becomes a floating, transparent window that stays on top.
  3. Work: User types through the ghost window in their IDE/Design tool, using the overlay as a direct visual guide.
  4. Dismiss: A global hotkey toggles visibility or dismisses the ghost when done.

4. Target Audience

  • Primary Persona: The “Pixel-Perfect” Frontend Developer.
    • Pain Point: Constantly switching between Figma and VS Code to match padding/colors, losing context and flow.
  • Secondary: Digital Artists (tracing references), Data Entry Clerks (transcribing text from images).

5. MVP Feature Set

  • Ghost Windows: Create up to 3 simultaneous overlay windows.
  • Click-Through Mode: Toggle that makes the overlay ignore mouse events (allowing interaction with the app behind it).
  • Opacity Slider: Global hotkey + Scroll wheel to adjust transparency (10% - 100%).
  • Source Support:
    • Image Files (Drag & Drop)
    • Screen Region Capture (Snipping tool style)
    • URL (render a live website as an overlay - e.g., mobile view of localhost)
  • Hiding: “Panic Key” to instantly hide all overlays.

Future Scope:

  • OCR on overlays (copy text from the image).
  • Video overlays (watch tutorial while coding).
  • Team Sync (share overlay sets).

6. Tech Stack Recommendation

  • Frontend/Core: Tauri v2 (Rust + React/TypeScript).
    • Why: Critical for minimizing RAM usage (Electron is too heavy for a background utility) and accessing native OS window traits (NSWindow on macOS, SetWindowLong on Windows) for click-through transparency.
  • State Management: Rust Backend (managing window handles) -> Frontend (UI for settings).
  • Distribution:
    • macOS: DMG/Updater (Notarized).
    • Windows: NSIS Installer.
    • Linux: AppImage.

7. Technical Challenges & Mitigations

1. Click-Through Transparency

Risk: OS support varies wildly. Windows requires specific flag combinations; macOS needs `ignoresMouseEvents`. Linux (Wayland) is strict about window positioning.

Mitigation: Use the `tauri-plugin-window-state` and custom Rust commands to invoke platform-specific APIs. Fallback to "always on top but not click-through" for Wayland.

2. Performance Overhead

Risk: Overlays causing input lag in the underlying high-performance app (e.g., Blender, Game Engine).

Mitigation: Use GPU acceleration for the webview but ensure the Rust backend process runs at normal priority. Enforce strict resource limits on the WebView.

3. macOS Permissions

Risk: Screen recording permission is required for the "Region Capture" feature.

Mitigation: Implement a "Check & Request" flow on first launch explaining *why* it's needed (not for spying, but for local cropping).

8. Monetization Strategy

  • Model: Freemium.
  • Free Tier: 1 active overlay, Image support only.
  • Pro Tier ($29 One-Time License): Unlimited overlays, URL/Web support, “Save Workspaces”.
  • Sustainability: Zero server cost (local app). One-time payment aligns with the “Power Tool” utility market.

9. Compliance & Distribution

  • Privacy: 100% Local. No screen data ever leaves the device.
  • Stores:
    • Mac App Store: Risk - “Click-through” APIs might be flagged as non-standard behavior. Plan for Direct Distribution (DMG) as primary channel.
    • Microsoft Store: Generally permissible for desktop utilities.

10. Validation Metrics

  • Retention: “Daily Active Users” who toggle an overlay > 5 times/day.
  • Conversion: Free-to-Paid upgrade rate > 3%.
  • Performance: Overlay latency (time to move) < 16ms (60fps).