@media (max-width: 450px) {
    .logo img.b {
        width: 2.5rem;
        height: auto;}
}
.header-a a:hover{color:#e89b15;}
.nav-list li a:hover{font-size: 0.22rem;transition: 0.5s all;}
.nav-down li:hover{background:rgba(0,0,0,.7);}
.pull-left.logo-b img{
    max-width: 4rem;
    height: auto;}