如何使用css实现一个加载动画

如何使用css实现一个加载动画 有四个点 初始化为同一个颜色 每个阶段 不同的透明度 刷新也不会影响初始化

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
<div class="loading-container">
  <div class="loading-dot dot1"></div>
  <div class="loading-dot dot2"></div>
  <div class="loading-dot dot3"></div>
  <div class="loading-dot dot4"></div>
</div>
</body>
<style>

    /*加载动画开始*/
    .loading-container {
        padding: 5px 0;
        position: relative;
    }

    .loading-dot {
        width: 7px;
        height: 7px;
        border-radius: 50%;
        margin: 0 3px;
        background: #327eff;
        animation: loading 3s  infinite;
        float: left;
    }

    .dot1 {
        animation-delay: -1.5s;
    }

    .dot2 {
        animation-delay: -1s;
    }

    .dot3 {
        animation-delay: -0.5s;
    }

    .dot4 {
        animation-delay: 0s;
    }

    @keyframes loading {
        0% {
            opacity: 0.25;
        }
        50% {
            opacity:1;
        }

        100% {
            opacity: 0.25;
        }
    }
    /*加载动画结束*/
</style>
</html>