如何使用边框和变换将创建的箭头居中？

.arrow {
  width: 0;
  height: 0;
  border: solid transparent;
  border-width: 20px;
  border-bottom-color: #000; /* 箭头颜色 */
  transform: rotate(45deg); /* 旋转箭头，使其指向右上方 */
}

.container {
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh; /* 设置容器高度以居中显示 */
}

<div class="container">
  <div class="arrow"></div>
</div>