appearance

appearance: none;

appearance: auto;

<section id="default-example">
  <div class="background">
    <button id="example-element">button</button>
  </div>
</section>

.background {
  display: flex;
  place-content: center;
  place-items: center;
  width: 150px;
  height: 150px;
  background-color: white;
}

/* CSS 基本用户界面模块 Level 4 支持的值 */
appearance: none;
appearance: auto;
appearance: menulist-button;
appearance: textfield;

/* "compat-auto" 值与 "auto" 值具有相同的效果。 */
appearance: button;
appearance: searchfield;
appearance: textarea;
appearance: push-button;
appearance: slider-horizontal;
appearance: checkbox;
appearance: radio;
appearance: square-button;
appearance: menulist;
appearance: listbox;
appearance: meter;
appearance: progress-bar;

/* Gecko 中可用的部分值列表 */
-moz-appearance: scrollbarbutton-up;
-moz-appearance: button-bevel;

/* WebKit/Blink（以及 Gecko 和 Edge）中可用的部分值列表 */
-webkit-appearance: media-mute-button;
-webkit-appearance: caret;

/* 全局值 */
appearance: inherit;
appearance: initial;
appearance: revert;
appearance: revert-layer;
appearance: unset;

.exampleone {
  -webkit-appearance: menulist-button;
  -moz-appearance: menulist-button;
  appearance: menulist-button;
}

<select class="none">
  <option>appearance: none</option>
</select>
<select class="auto">
  <option>appearance: auto</option>
</select>

.none {
  appearance: none;
}
.auto {
  appearance: auto;
}