/** 简约输入框.css **/
.app{
    width: 100%;
    height: 97vh;
    background-color: #ffffff;
    position: relative;
    display: flex;
    justify-content: center;
    align-items: center;
}

label{
    position: relative;
}

input{
    width: 240px;
    height: 36px;
    line-height: 36px;
    outline-style: none;
    font-size: 16px;
    color: #333;
    border: none;
    padding: 0 8px;
    box-sizing: border-box;
    text-align: center;
}

.line{
    width: 0;
    height: 2px;
    display: block;
    background-color: #4158D0;
    background-image: linear-gradient(90deg, #4158D0 0%, #C850C0 48%, #FFCC70 100%);
    transition: all 0.24s ease-in-out;
}

input:focus+.line,input:valid+.line{
    width: 100%;
}