mobile-config-firefox/chrome/button_effect_scale_onclick.css

/* Effect */

:root:not([uidensity="compact"]) #back-button{ --uc-back-extra-padding: 2px }

.toolbarbutton-icon,
.menuitem-iconic .menu-iconic-icon{
  transition: transform 82ms linear !important;
}

toolbar .toolbarbutton-1 > .toolbarbutton-icon{
  transition: padding 82ms linear !important;
}

toolbarbutton:not(.toolbarbutton-1):active > .toolbarbutton-icon,
toolbar .toolbarbutton-1:not([disabled]):active > .toolbarbutton-badge-stack > .toolbarbutton-icon,
.menuitem-iconic:active .menu-iconic-icon{
  transform: scale(0.6) !important;
}

toolbar .toolbarbutton-1:not([disabled]):active > .toolbarbutton-icon{
  padding: calc(var(--toolbarbutton-inner-padding) + var(--uc-back-extra-padding,0px) + 3px) !important;
}