如何创建一个只包含字符的简单加载屏幕？

<div id="loading-screen"></div>

#loading-screen {
  background-color: #000;
  color: #fff;
  font-size: 24px;
  text-align: center;
  padding: 20px;
  animation: loading-animation 1s infinite;
}

@keyframes loading-animation {
  0% {
    content: ".";
  }
  33% {
    content: "..";
  }
  66% {
    content: "...";
  }
}

// 在页面加载完成后隐藏加载屏幕
window.addEventListener("load", function() {
  var loadingScreen = document.getElementById("loading-screen");
  loadingScreen.style.display = "none";
});