Japanese “Free Of Charge” Button
This is a Japanese symbol, which surrounds a Japanese character with an outer frame. This character looks a bit like the traditional Chinese word "No". This character means "free", or it may mean "lack" or "nothing".
In most platform emoticons, the frame of the logo is square, but the bottom frame of some platforms is relatively round, and the four corners are not right angles, but with a certain radian. As for the color of characters, most platforms use white, and some platforms use black or blue. As for the background color of the frame, it also varies from platform to platform, including blue, orange, white and gray.
