Function
Without a shell, a navigation holds the learner on the page they came from until the whole payload lands — measured at several seconds on a throttled phone — and they read that stale page as the one they asked for. This gives Next something to swap in on the first frame instead.
The shapes trace the new-visitor home, which is what the server renders: the editorial hero on its twelve-column grid with the vowel-length card beside it, the numbered questions, the levels table and the reference table. The classes are the page's own, so the arriving content fills positions that are already correct.
Two level rows and one reference row, because the catalog ships two level courses and one reference course today; a shell that guessed more would promise rows the tables never draw.
The home's loading shell.