header {position: fixed; background-color: #fff; width: 100%; z-index: 1; border-bottom: 1px solid #eee;}
header h1 {position: relative;}
header h1 a {display: block; padding: 2rem 1.5rem; text-align: center;}
header h1 a img {height: 2.8rem;}
header h1 button {position: absolute; top: 0; left: 0; width: 4.5rem; height: 100%; background: url("../sub/arrow_blue.png") no-repeat center / 1rem; border: none;}