Effective 40mm fan guard

I broke my 4th 40mm fan today. The problem with all other fan guards I've seen so far is that they do not intercept any tools headed for the fan blades.

This is inspired by Japanese fences that block the view, but not the wind.

The initial version is a proof-of-concept that was quickly put together, so you can still attack the fan blades from cerrtain angles -- but this should trap the most likely direction of tools headed for the fan.