header {
    background-color: rgb(0, 0, 0);
    width: 100%;
    padding: 10px 4%;
    position: fixed;
    top: 0;
    left: 0;
    display: flex;
    justify-content: space-between;
    align-items: center;
    z-index: 1000;
    box-sizing: border-box;
}

#page_name {
    color: rgb(255, 255, 255);
    font-size: 1.4em;
    font-family: "Noto Sans", "Noto Sans JP";
    letter-spacing: 7px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.header_list {
    position: absolute;
    top: 50%;
    right: 0;
    transform: translateY(-50%);
    padding: 3vw;
}

.header_link {
    color: rgb(255, 255, 255);
    font-family: "Noto Sans", "Noto Sans JP";
    text-decoration: none;
    font-size: 25px;
    padding: 0 15px;
}

.menu-icon {
    display: none;
    flex-direction: column;
    justify-content: space-around;
    width: 30px;
    height: 25px;
    background: transparent;
    border: none;
    cursor: pointer;
    padding: 0;
    z-index: 10;
}

.menu-icon .bar {
    width: 100%;
    height: 4px;
    background-color: #fff;
    margin: 4px 0;
    transition: 0.4s;
}

.menu-icon .bar.active:nth-child(1) {
    transform: rotate(-45deg) translate(-5px, 6px);
}

.menu-icon .bar.active:nth-child(2) {
    opacity: 0;
}

.menu-icon .bar.active:nth-child(3) {
    transform: rotate(45deg) translate(-5px, -6px);
}

.nav-menu {
    display: none;
    position: absolute;
    top: 50px;
    right: 10px;
    background-color: white;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
    border-radius: 4px;
    width: 200px;
    transition: max-height 0.4s ease-in-out;
    overflow: hidden;
    max-height: 0;
}

.nav-menu ul {
    list-style: none;
    padding: 0;
    margin: 0;
}

.nav-menu ul li {
    border-bottom: 1px solid #ddd;
}

.nav-menu ul li a {
    display: block;
    padding: 10px 20px;
    color: #333;
    text-decoration: none;
}

.nav-menu ul li a:hover {
    background-color: #f5f5f5;
}

.show-menu {
    max-height: 300px;
    display: block;
}

@media screen and (max-width: 640px) {
    .pc-nav {
        display: none;
    }

    .menu-icon {
        display: flex;
    }

    #page_name {
        font-size: 1em;
        width: 80%;
    }
}

body {
    padding-top: 60px;
    margin: 0;
}