/* ==================================================
   Header
================================================== */

#header {
    position: sticky;
    top: 0;
    z-index: 900;

    width: 100%;
}

.site-header {
    width: 100%;

    background: rgba(255, 255, 255, 0.80);

    border-bottom: 1px solid var(--color-border);

    backdrop-filter: blur(14px);
}

.header-inner {
    width: min(
        var(--content-width),
        calc(100% - var(--side-padding) * 2)
    );

    min-height: 64px;

    margin: 0 auto;

    display: flex;
    align-items: center;
    justify-content: space-between;

    gap: 30px;
}

.menu-button {
    display: none;

    align-items: center;
    justify-content: center;

    width: 44px;
    height: 44px;

    padding: 0;

    border: none;
    background: transparent;

    color: var(--color-text);

    font-size: 24px;
    cursor: pointer;
}

.mobile-menu {
    display: none;
}

/* Logo */

.site-logo {
    display: inline-flex;
    align-items: center;

    gap: 10px;

    font-weight: var(--font-weight-heavy);
}

.site-logo-mark {
    width: 34px;
    height: 34px;

    display: flex;
    align-items: center;
    justify-content: center;

    border-radius: 10px;

    color: white;
    background: var(--color-primary);

    font-size: 17px;
}

.site-logo-name {
    color: var(--color-heading);

    font-size: var(--font-size-subtitle);

    letter-spacing: 0.03em;
}


/* Navigation */

.site-nav {
    display: flex;
    align-items: center;

    gap: 22px;
}

.site-nav a {
    position: relative;

    padding: 4px 0;

    color: var(--color-text-sub);

    font-size: var(--font-size-small);
    font-weight: var(--font-weight-bold);

    letter-spacing: 0.08em;

    transition:
        color 0.2s ease;
}

.site-nav a:hover,
.site-nav a.active {
    color: var(--color-primary-dark);
}

.site-nav a.active::after {
    content: "";

    position: absolute;

    left: 0;
    right: 0;
    bottom: -4px;

    height: 2px;

    border-radius: 999px;

    background: var(--color-primary);
}

/* ==================================================
   Responsive
================================================== */

@media (max-width: 640px) {

    /* PC用ナビを非表示 */
    .site-nav {
        display: none;
    }

    /* ハンバーガーボタン */
    .menu-button {
        display: flex;
    }

    /* 全画面メニュー */
    .mobile-menu {
        position: fixed;
        inset: 0;
        
        z-index: 1000;

        display: flex;
        align-items: center;
        justify-content: center;

        background: var(--color-background);

        opacity: 0;
        visibility: hidden;

        transition:
            opacity 0.2s ease,
            visibility 0.2s ease;
    }

    /* 開いた状態 */
    .mobile-menu.is-open {
        opacity: 1;
        visibility: visible;
    }

    /* メニュー項目 */
    .mobile-menu-links {
        display: flex;
        flex-direction: column;
        align-items: center;

        gap: 28px;
    }

    .mobile-menu-links a {
        color: var(--color-text);
        text-decoration: none;

        font-size: 24px;
        font-weight: var(--font-weight-bold);

        transition:
            color 0.2s ease,
            transform 0.2s ease;
    }

    .mobile-menu-links a:hover {
        color: var(--color-primary);
        transform: translateX(4px);
    }

    .mobile-menu-links a.active {
        color: var(--color-primary);
    }

    /* ×ボタン */
    .menu-close-button {
        position: absolute;
        top: 16px;
        right: 16px;

        width: 48px;
        height: 48px;

        padding: 0;

        border: none;
        background: transparent;

        color: var(--color-text);

        font-size: 32px;
        font-weight: 300;

        cursor: pointer;
    }
}

@media (min-width: 701px) {
    .mobile-menu {
        display: none;
    }
}