Assessment wanted for Fundamental Layout Comprehension - 2021-01-31

My assessment project code link: https://github.com/Zheng7426/MDN-Doc-Practice/blob/main/css/fundamental_layout_comprehension/styles.css

The end result is shown below:
(Mobile & tablet screen)

(Desktop screen)

When we define media queries, can we write one breakpoint as 70em and the other one for mobile as 69em?

@media screen and (max-width: 69em) { ... }
@media screen and (min-width: 70em) { ... }

If you have any suggestions please share them! Thank you.