Using safe-area-inset to build mobile-safe layouts

Modern smartphones have physical features like notches, camera cutouts, and home indicators that can obscure content, which browsers expose as "safe area insets" that developers can access via CSS environment variables. Using the `env(safe-area-inset-*)` values in CSS allows developers to adjust padding and positioning so important content and interactive elements remain visible and accessible, particularly for floating buttons and other UI components. Safe area insets are now widely supported across browsers and can be easily implemented with fallback values for maximum compatibility.