Lettermin is a responsive website that offers a selection of typefaces made by a type designer. The first step in the purchase flow consists of selecting the typeface, subfamily, license, and styles. The form can get long when visiting the website with a smartphone or a tablet.
Despite taking the necessary steps to prevent a person from missing out on a required input field, the scenario is still possible. Finding out that a required field is missing when the person is at the bottom of the form causes friction.
After conducting usability testing, the solution we decided to build is based on the Poka-Yoke principle. If the person misses a required input field, a call to action button with the missing input field label is displayed instead of the usual "Continue" button. The user taps the button and is taken directly to the missing field. There's no need to scroll and manually searching the input field.