Responsive landing page mobile first using CSS Flexbox

What are you most proud of, and what would you do differently next time?

It was the first landing page do it by myself :D

What challenges did you encounter, and how did you overcome them?

Responsive was difficult, but the usage of the measures of viewport width and viewport height help.

I have troubles with the circles in responsive, there are certains viewport measures were the icons in the circles looks out of place.

The image of the mockup was also problematic. In certain measurements of the viewport it crossed the container. I fixed it by letting the container height be automatic and setting the minimum (for the original layout look) and maximum height.

What specific areas of your project would you like help with?

Is a good practice use viewport width and viewport height? I find it much better for responsive design.

How can i fix the looks of the icons in the circles?

All constructive feedback is welcome.