CSS的position定位布局问题

HTML部分

<header class="header">
    <div class="container">
        <div class="logo">
            <a href="#"><img src="img/logo.svg" alt="logo"></a>
        </div>
        <div class="menu"></div>
    </div>
</header>

CSS部分

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
}

.header {
    background: rgba(255,255,255,.5);
    width: 100%;
    height: 100px;
    line-height: 100px;
    font-size: 20px;
    position: fixed;
    overflow: hidden;
    z-index: 99;
}

.logo,
.menu {
    position: absolute;
    top: 50%;
    -webkit-transform: translate(0,-50%);
       -moz-transform: translate(0,-50%);
        -ms-transform: translate(0,-50%);
         -o-transform: translate(0,-50%);
            transform: translate(0,-50%);
}

.logo {
    width: 90px;
    height: 60px;
}

.logo img {
    width: 100%;
    position: absolute;
    top: 0;
}

.menu {
    right: 0;
    background: #45b29a;
    width: 60px;
    height: 60px;
    border-radius: 50%;
}

这是实际效果：