li button.icon-webrtc-voice:before {
  background-image: image-set(url("/contacts/style/webrtc-client/images/actionicon_contacts_webrtc_audio.png") 1x, url("/contacts/style/webrtc-client/images/actionicon_contacts_webrtc_audio@1.5x.png") 1.5x, url("/contacts/style/webrtc-client/images/actionicon_contacts_webrtc_audio@2x.png") 2x, url("/contacts/style/webrtc-client/images/actionicon_contacts_webrtc_audio@2.25x.png") 2.25x);
  background-size: 3rem;
}

li button.icon-webrtc-video:before {
  background-image: image-set(url("/contacts/style/webrtc-client/images/actionicon_contacts_webrtc_video.png") 1x, url("/contacts/style/webrtc-client/images/actionicon_contacts_webrtc_video@1.5x.png") 1.5x, url("/contacts/style/webrtc-client/images/actionicon_contacts_webrtc_video@2x.png") 2x, url("/contacts/style/webrtc-client/images/actionicon_contacts_webrtc_video@2.25x.png") 2.25x);
  background-size: 3rem;
}