naive-ui/styles/themes/light/components/BackTop.scss

@mixin setup-light-back-top {
  $--back-top-button-fill: rgba(0, 0, 0, .6) !global;
  $--back-top-button-fill-hover: rgba(0, 0, 0, .5) !global;
  $--back-top-button-fill-active: rgba(0, 0, 0, .7) !global;
  $--back-top-box-shadow: (
    'default': 0 2px 8px 0px rgba(0, 0, 0, .12),
    'hover': 0 2px 12px 0px rgba(0, 0, 0, .18),
    'active': 0 2px 12px 0px rgba(0, 0, 0, .18)
  ) !global;
}