countzero/ai_room_planner — reverse-engineered prompt

Build me a simple browser based 2D room planner that works by just opening an HTML file, with no install step and no framework.

I want users to draw floor plans on a canvas by clicking to create walls, closing shapes into rooms, adding doors, windows, and text labels, then selecting things to edit their properties. Show wall lengths in meters, room areas, overall plan dimensions, and a live cursor position. Make it feel polished with snapping to a grid, angle snapping, zoom, pan, fit to view, undo and redo, and keyboard shortcuts.

Please include auto save in the browser, import and export as JSON, export as PNG and SVG, dark and light mode, a rooms list with total area, and small toast messages for actions like saving or exporting.

Keep it all vanilla JavaScript, HTML, and CSS. Organize the code clearly so it’s maintainable, and make the UI friendly enough for someone planning a room layout casually.