Fog of war

Fog

???

▅▅▅▅

▅▅ ▅▅ !

Also, I wonder that where there is nothing on the diagonal from a pawn that should be shown as blank not rain cloud.

Yes but the aesthetic of the ruddy rain cloud doesn't go away!..

I still prefer the original empty squares.

You can turn off the "fog" and go back to how it was.

Click the settings cog in the top/middle of the page, and turn off the setting listed as "Use Fog Of War background image " under the "Board" tab

We requested it a few weeks ago and an admin fixed it

is this blindfold chess?

No. Blindfold chess you hear the opponents move and you just have to keep track in your mind. 

Fog of war, you don't know what your opponent is doing at all, unless your piece is in range to attack it. 

blind chess