Clipboard Landing Page with Sass and Flexbox

I have been trying and trying to get the computer and device images to resize for smaller screens. They resize when I shrink the browser, and they look fine in Firefox's web developer tool device simulators. When I view the solution on my phone, however, the images are still full size. I'm not quite finished with this project- I want to nail this design, and I keep tweaking the different sections to get the spacing and positioning just right- so I would very much appreciate any advice anyone can give me. Thank you!