3-column preview card using mobile-first css, flexbox

Hi!

I have free subscription and I'm doing the newbie challenges one by one. I have a question.

When doing the job, what is the best practice to compare the desktop and the mobile desig files with my solutions and part-solutions?

Now I run the index.html on the vs code live server, in chrome. After I open in the background the design images and push the ALT+TAB several times and try to see the differences.

Maybe there are a better method, what is more precise. If there is, please explain me.

Thank you!