Checkout

a short cart: contact, delivery and payment stacked in one form beside a sticky summary

a long form or a phone: three steps, finished ones folded to a one-line recap with « Modifier »

a signed-in customer with a saved address and card: one card of rows, each editable alone, then one pay button

a calm, focused checkout with a few items: one centred column at every width, a summary bar that opens the lines, contact, delivery and payment stacked, one pay button