Videos play from videos/<category folder>/, right next to this file.
Each category owns one subfolder, matched by name. When adding an exercise, pick the category first, then type
the file name or use Browse to fill it in (Browse only reads the name — put the actual mp4 in that
folder yourself). Everything you add is saved in this browser (localStorage) — use Backup
occasionally so a cleared browser can't lose your library.
Categories
Routines
Add exercise
New category
New routine
No local video file for this one yet — use Watch reference or add a file name in Edit.