Two columns. Left: "Pay Copy in Public", the big amount, line items, promo code BUILDINPUBLIC for 100% off, total due. Right: Apple Pay button, OR divider, email, card number with brand badges, MM / YY + CVC in a grouped input, cardholder name, country + ZIP, the Link save box, and the blue Pay button with the spinner.

Card number formats as you type. Pay shows "Processing…", then "Copying card…", then the success screen. Nothing is sent anywhere; there is no backend for this page at all. Check the network tab.