gnome-shell-dark-theme/gnome-shell-sass/widgets/_a11y.scss

// Pointer location
.ripple-pointer-location {
  width: $ripple_size;
  height: $ripple_size;
  border-radius: $ripple_size * 0.5; // radius equals the size of the box to give us the curve
  background-color: st-lighten(st-transparentize(-st-accent-color, 0.7), 30%);
  box-shadow: 0 0 2px 2px st-lighten(-st-accent-color, 20%);
}

// Pointer accessibility notifications
.pie-timer {
  width: 60px;
  height: 60px;
  -pie-border-width: 3px;
  -pie-border-color: -st-accent-color;
  -pie-background-color: st-lighten(st-transparentize(-st-accent-color, 0.7), 40%);
}

// Screen zoom/Magnifier
.magnifier-zoom-region {
  border: 2px solid -st-accent-color;

  &.full-screen { border-width: 0; }
}