SOURCE

<p> <a href="https://mp.weixin.qq.com/s/Z7WjUJuB0tYxcHWoraqxJw"> 来源 </a></p>
<div>123</div>

div {
    width:600px;
    height: 600px;
    background: 
        conic-gradient(from 270deg at 20px 5px, #31c2ec 90deg, transparent 0deg),
        conic-gradient(from 270deg at 5px 20px, #31c2ec 90deg, transparent 0deg),
        repeating-linear-gradient(90deg,#aec8ee 0, #aec8ee 1px, transparent 1px, transparent 100px),
        repeating-linear-gradient(#aec8ee 0, #aec8ee 1px, transparent 1px, transparent 100px),
        #0e284d;
    background-repeat: repeat, repeat, no-repeat, no-repeat;
    background-size: 
        100px 100px,
        100px 100px,
        100% 100%,
        100% 100%;
    background-position: 
        -10px -2.5px,
        -2.5px -10px,
        0 0,
        0 0;
}