Step 1: Go to a YouTube URL. (e.g. https://www.youtube.com/watch?v=dQw4w9WgXcQ)
Step 2: Add "magic" between "you" and "tube". (e.g. https://www.youmagictube.com/watch?v=dQw4w9WgXcQ)
Step 3: Click "Download Video".
Step 4: Enjoy watching it offline!