Responsive Huddle landing page using grid

I have recently learnt the grid layout in CSS and decided to implement this into this design to test even though it is a basic design. I also changed the grid layout to flex for when it is mobile as it will only ever need a 1 dimensional layout for mobile. Is this a good way to go about the structure or should I have left it as grid and just make it drop down for mobile? I also couldn't get the icon border to be a perfect circle it was showing as an ellipse no matter what I changed with the width and height. Any help is much appreciated on this.