AutoGUI controls the mouse and keyboard, takes screenshots, finds images on the screen, shows message boxes, and inspects application windows. It is a Ruby port of Python PyAutoGUI with snake_case methods and CamelCase aliases. Windows talks to the Win32 API through Ruby's standard-library Fiddle (no extra gems). macOS uses osascript and screencapture. Linux uses xdotool plus scrot, ImageMagick, or grim. Fail-safe: moving the cursor into a screen corner raises FailSafeException.