Hipstersavvy1/pytube-downloader ? reverse-engineered prompt

Build me a desktop app that lets me paste a YouTube video or playlist link and download it easily.

I want a clean, modern window with an easy to use interface, progress tracking, and the ability to choose between downloading a single video or a whole playlist. It should let me pick the format and quality, like MP4 or MP3, and support different resolutions, with multiple downloads happening at the same time. Please also make it remember my preferred settings so I can reuse them without changing everything every time.

Organize the downloaded files in a sensible way, like separating playlists and file types into folders. Add support for more than one language if possible, and make it work on Windows, Linux, and macOS. Use FFmpeg when needed for converting audio and video, and include basic error handling and logs so it is easier to tell what went wrong. If you need to check current library docs while building it, go ahead and look them up online.