How to make the clarity of the icons in IOS?

Good time of day. There is a website with this slider dg-education.com/chastnye-shkoly-v-shveycarija top of the page. The customer says that when you view the Iphone\Macbook and all IOS icons are shown blurry, at least on Windows/Android seems to be as well. Heard something about device-pixel-ratio, but can't really understand how to use it. Those who have experienced this? I would be grateful for any advice.
July 12th 19 at 17:06
2 answers
July 12th 19 at 17:08
July 12th 19 at 17:10

Find more questions by tags IconsHTMLCSSiOS