Comment by captainmuon

It's just a shader, so maybe not in pure CSS, but you could probably achive something like that in WebGL.

About "only Apple can achive that": It would be pretty simple for MS to do something like this in Windows. DirectComposition (or whatever it is called nowadays) could set the appropriate shader when drawing windows. You cannot do it as a normal user, because you can only pick from a select set of backdrop shaders (but if some hacker wants a challenge, you could inject the code into dwm.exe to do so :-)).