node_modules/@angular/cdk/_a11y.scss

@mixin cdk-a11y {
  .cdk-visually-hidden {
    border: 0;
    clip: rect(0 0 0 0);
    height: 1px;
    margin: -1px;
    overflow: hidden;
    padding: 0;
    position: absolute;
    width: 1px;

    // Avoid browsers rendering the focus ring in some cases.
    outline: 0;

    // Avoid some cases where the browser will still render the native controls (see #9049).
    -webkit-appearance: none;
    -moz-appearance: none;
  }
}

// Applies styles for users in high contrast mode. Note that this only applies
// to Microsoft browsers. Chrome can be included by checking for the `html[hc]`
// attribute, however Chrome handles high contrast differently.
//
// @param target Which kind of high contrast setting to target. Defaults to `active`, can be
//    `white-on-black` or `black-on-white`.
@mixin cdk-high-contrast($target: active) {
  @media (-ms-high-contrast: $target) {
    @content;
  }
}