SerenityOS is an open-source OS targeting the power-user market. A "love letter to '90s user interfaces," Serenity takes a unique approach to the graphical Unix-like operating system. The backend of the operating system is completely custom, operating, in theory, like Unix - but it uses a cohesive collection of custom system services, in a manner similar to macOS (in that the system services have been built at the same time). POSIX threading and signals, "I/O redirection," a Unix-like libc, and the ex2 file system are also used. For the graphical user interface, contributors have pulled off a comprehensive copy of Windows 95. Modern Markdown and JavaScript libraries, a custom web browser and email client, piano software and "various" games are also included. It feels like you're in the 1990s - but the project takes this as its key strengths. Serenity sure does have a unique position in the game and fulfills a gap in the game.