css3 盒子线性流动效果

        .box{
            position: relative;
            width:180px;
            height:250px;
            background: rgba(0,0,0,0.8);
            border-radius: 20px;
            display: flex;
            justify-content:center;
            align-items: center;
            overflow: hidden;

        }
        .box::before{
            content:'';
            position:absolute;
            width: 100px;
            height: 120%; 
            background:linear-gradient(#ffd900,#f9000c);
            animation:lineRoll 3s linear infinite;
        }
        @keyframes lineRoll{
            0%{
                transform: rotate(0deg);
            }
            50%{
                transform: rotate(180deg);

            }
            to{
                transform: rotate(360deg);
            }
        }
        .box::after{
            content: '';
            position: absolute;
            background: #795548;
            right:4px;
            top:4px;
            left:4px;
            bottom:4px;
            border-radius: 20px;  
        }
        .box h2{
            text-align: center;
            color:white;
            font-size:3em;
            text-shadow:2px 2px pink;
            z-index:1;
        }

    <div class="box">
        <h2>线性流动</h2>
    </div>