The product is a working prototype, not a set of flat mockups. It is a single 168 KB HTML file with vanilla JavaScript and zero network requests. Ten screens are wired together: welcome, choose your split, home, a save pot, move money, success, activity, settings, plus a designed empty state and a designed error state. You can pick a split, open a pot, type an amount on the keypad, review it in a bottom sheet and confirm. Flip "Simulate a failed transfer" in Settings and the same flow lands on the error screen instead.