The book centers around a concept you've coined the hook cycle, which consists of triggers, action, variable reward, and investment. Can you walk us through each of these and their impact on designing habit forming products? Sure. What is it about these companies that can so profoundly change user behavior? And it turns out there is the common element is called the hook. The hook is an experience design to connect the user's problem with the company's product with enough frequency to form a habit. These hooks are embedded into the product design. It literally is the user experience, the flow that users go through and using the product touches these four steps to form these core habits.