While the term Responsive User Interface is often associated with Web development, it is in fact crucial on all platforms: Android supports smartphones, foldables, and tablets; iOS apps should look great on iPhones and iPads; Linux, macOS, and Windows have been supporting multiple resizable windows for decades. So, no matter which platform you look at, apps always face different form factors and screen sizes. How do we cater for this? How do we make sure that our apps look great everywhere? In this talk, I'll show you how Jetpack Compose, Canonical layouts, Window Size Classes, and Material 3 Adaptive help you make your app shine regardless the platform, screen size, and form factor.