keycastr/keycastr ? reverse-engineered prompt

Build me a simple macOS app that shows my keystrokes on screen while I’m recording a video or giving a demo.

I want it to display key presses in a small floating overlay, with options to show just command keys, all modified keys, or every keystroke. It should also have an option to show mouse clicks. The overlay should start near the bottom left, but I want to be able to drag it anywhere on the screen.

Make it feel like a normal Mac app, with a menu bar icon and a preferences window where I can change what gets shown. It should ask for the right macOS permissions to listen for keyboard and mouse events, and help me understand what to do if it is not working because of privacy settings or if the overlay is off screen.

Please keep it open source friendly and simple, and if you need to check current macOS docs or best practices, look them up online.