body,

html {

    width: 100%;

    height: 100%;

    display: flex;

}

​

div {

    margin: auto;

    width: 500px;

    height: 500px;

    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;

}

​