Icon Theme: Adjust logo image size for mobile only

Some stores might struggle with controlling the size of their logo images on mobile.
Luckily there is a simple copy and paste code snippet which will help add some control and sharpness.

Open: Online store > themes > ... > Edit Html / Css

On the next page open: Assets > Queries.css.liquid
Scroll to the very bottom of the page and paste in the following:

@media screen and ( max-width: 740px ) {
#logo img { max-width: 180px; }

You may increase/decrease the 180px value to your preference. 
Click save and test.