Micro-Interactions That Change How a Product Feels A button that reacts when you hover. A form field that gently shakes when you get the password wrong. A success checkmark that draws itself.   None of these change what the product does. All of them change how it feels.   Micro-interactions are the difference between "this works" and "this feels alive." They're also the easiest place for a product to quietly build trust.   My rule: if a user action has a consequence, the interface should acknowledge it within 100ms.   Small details. Big retention impact.