body {
    background-repeat: no-repeat;  
    background: rgba(12, 100, 129, 0) url('https://img2018.cnblogs.com/blog/1732610/201907/1732610-20190704032451050-1073828859.jpg') fixed;
    background-position: 100%  50%; 
    background-size: 100% auto;
}