The release of our skins for Roundcube 9.x brought about the best and the latest that technology has to offer. One of the major improvements was including SVG images in all the mobile skins.
And what's so great about SVG? It solves icon display problems on the modern high-resolution smartphones. Because the smartphone screens nowadays use more and smaller pixels, they scale up whatever they display to make it readable to human eyes. When fonts are scaled it's not a problem because they are vector-based and when their size changes they don't lose quality. But images like JPEG or PNG are not vector-based and when they scale up, they become blurred.