Seelen-UI

Seelen UI is a project that replaces big parts of the Windows desktop so the operating system looks and behaves the way you want. It is not a theme pack or a skin pasted over the existing interface. It actually swaps out things like the taskbar, the dock, the app launcher, the window manager, the notification flyouts, and the virtual desktops with its own versions, and lets you restyle each of them. The README describes it as a full desktop environment replacement for Windows 10 and 11, available in over seventy languages.

You can install it from the Microsoft Store. Once running, the look is driven by a theming engine that uses CSS and JSON, so colours, fonts, borders and animations can be edited or shared as community themes. There is a dynamic accent feature that picks colours from your wallpaper automatically. A tiling window manager arranges your open programs into keyboard-controlled layouts with configurable gaps, and you can mark specific apps as floating or pin them to particular workspaces. A keyboard-driven app launcher inspired by Rofi finds apps, files and commands with fuzzy search. There are also desktop widgets, an alt-tab replacement, media controls, custom flyouts for things like volume and brightness, and per-workspace wallpapers.

Someone would use Seelen UI when they want a tiled, keyboard-first, heavily customised desktop on Windows without leaving Windows entirely. It is aimed at power users who would otherwise be drawn to Linux tiling setups, but also at anyone who simply wants Windows to look different. The project's primary language is Rust, and configuration lives in standard CSS and JSON files so themes and widgets can be shared between users.