It adds smart API endpoint selection with fallbacks between normal and preview environments and multiple Duolingo API versions, stores all settings (iterations, speed mode, custom interval, window position, and lifetime gems) in a shared cookie so they persist and sync across all Duolingo subdomains, introduces multiple speed presets plus a custom speed with interruptible sleeps for instant stopping, and significantly enhances the UI (draggable, responsive, more stats including, and a reset button).
