X11 window manager inspired by Plan 9's rio

 It provides a very simple and clean user interface. It is click-to-type. It
 uses the X11 font system (which, unfortunately, means no Unicode support).
 .
 9wm does not provide virtual desktops, customization, key bindings, EWMH
 support, or compositing. It does not allocate any colors, which will be
 great news if you are stuck in 1993.
 .
 It is a great place to start if you are interested in writing a window
 manager from scratch: many folks have done exactly this.