Checkout & payments

A promo-code row: Apply shows a spinner, a valid code becomes a removable chip and the total counts down.

Percentage tip buttons that show the cash amount under each, plus a Custom option that opens a small input.

A cart nudge showing how far you are from free shipping; the bar fills and the message flips when unlocked.

A trial status card: a segmented bar of days used, what you keep and lose, and a CTA that firms up near the end.