css-calc,transform-matrix，transtion配合hover来用

a{
    width: calc(100% - 100px); // a标签的宽度为父元素的100%再减去100px   
}

a{
    transform: matrix(0.866,0.5,-0.5,0.866,0,0); // a标签2d转换，cool
}

a{
    width: 500px;
    transtion: .3s all ease-in-out;
}
a:hover{
    width: 100px;
}