用代码说话

 section.tt-grid-wrapper{
    &:hover{
        background-image{
            -webkit-animation: pulse 2.0s infinite ease-in-out;
            animation: pulse 2.0s infinite ease-in-out;
        }
    }   
}

想让该选区在鼠标点击时，只让背景图执行动画，这样的less写法有错，求指点！！