Regular user โ€” sees only the base $100 limit, no bonus row.
Special-round user โ€” base $100 + bonus from special sale round (1:1 against existing balance credits, capped at $10,000 total).
Filled state โ€” Buy button enabled; amount validated against total limit (Max fills the full allowance).
Success screen โ€” shows credits purchased, their $ value, and the actual amount paid at $0.2/credit.