This invite form is designed to let users easily recommend MixLink to colleagues. There's a card that prominently features a promotional rate, which initiates the invitation modal.
Each field is validated to ensure that it's a unique, valid email address. As the user makes recommendations, additional email fields appear and the progress indicator advances. A pre-written message is sent on behalf of the user using SendGrid. Once 10 invitations have been sent, the user's account is updated and they are granted unlimited access until the promotion period ends.
Here's the a little bit more about why I designed this and what I was thinking about: