Here you go — a clean, single-file **Online Whiteboard** that’s full-screen, has pen/eraser, brush size & color, clear, and a reliable **Save as PNG**.
Just save this as `whiteboard.html` and open it in your browser.
```html
Online Whiteboard
Shortcuts: P (pen), E (eraser), Ctrl/⌘+S (save), Ctrl/⌘+K (clear)