Design System Transformation - The new design system redesigns the Mac window appearance, framing key structural regions in glass [1] - Toolbar elements are placed on a glass material, creating a floating effect and enhancing hierarchy [1] Control Grouping and Adaptability - AppKit automatically groups toolbar buttons representing singular actions on one piece of glass [2] - Different control types (segmented controls, pop-up buttons, search control) are separated into their own glass elements [2] - The Liquid Glass material adapts to its context, changing appearance based on the brightness of the content behind it [3] - The toolbar glass switches between light and dark appearance based on the scrolled content's brightness [3] Dark Mode Support - Appearance changes are communicated using the NSAppearance system, ensuring Dark Mode support [4]