For the “The Smash Brothers Logo” you are talking about the circle with a cross through it?

Smash Brother’s brings a lot of video game worlds together in one game so,

It was important to have one symbol that brought all of them together.It was designed to be very simple.

The cross represents that this game is a cross over (For example in things like anime where you have different worlds joining together), and the four sections represent the four player battles. The reason for the difference between thickness of the lines is…umm I forgot.