For years, JavaScript has been the default answer for almost every interactive detail on the web. Need a modal, a dropdown, dark mode, smooth scrolling, or form validation? Most frontend developers reach for JavaScript without thinking twice. But the platform has changed. This book shows how much modern HTML and CSS can already do on their own. Through practical examples, you will learn how to build real interface patterns with less code, fewer dependencies, and a stronger focus on accessibility, performance, and maintainability. You will explore features such as :has(), native dialogs, accordions, sliders, counters, dark mode, smooth scrolling, form validation, border animations, view transitions, motion paths, and mask effects. The book also introduces newer browser features like popovers, anchor positioning, scroll-driven animations, customizable selects, and CSS carousels. The goal is not to avoid JavaScript at all costs. It is to use it when it actually adds value, and not by default. By the end of the book, you will have a clearer sense of what the platform can handle today and how to build interfaces that are lighter, cleaner, and more resilient.