How can I set the font size in sparkweb

I posted a discuss in sparkweb support, but it seems sparkweb can not change font size without editing the source. So I downloaded it, but I found it is hard to know where to modify in order to change the font size in the chatroom.

I even replaced all fontsize notations with a large font size. The font size of logoin window changes, but nothing changes in the editbox and the history message box.

Anyone know how to change the font size? Thank you.

This is what I just did! However it does not change the font in the chat box…