如何使用CSS在视频上创建黑色覆盖？

<div class="video-container">
  <video src="video.mp4" controls></video>
</div>

.video-container {
  position: relative;
}

.video-container::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: black;
  opacity: 0.5; /* 调整透明度 */
}