/* ==========================================================================
   Sticky glass header
   ========================================================================== */
.site-header { position: relative; z-index: 1050; }

.site-nav.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1050;
    display: block;
    height: var(--header-h);
    padding: 0;
    background: transparent;
    border-bottom: 1px solid transparent;
    transition: background-color .3s ease, border-color .3s ease, box-shadow .3s ease;
}
.site-nav.navbar.scrolled,
body.nav-open .site-nav.navbar {
    background: var(--header-bg);
    border-bottom-color: var(--border);
    -webkit-backdrop-filter: saturate(180%) blur(18px);
    backdrop-filter: saturate(180%) blur(18px);
}
/* sub-pages (no hero) always show the glass header */
body.has-solid-header .site-nav.navbar {
    background: var(--header-bg);
    border-bottom-color: var(--border);
    -webkit-backdrop-filter: saturate(180%) blur(18px);
    backdrop-filter: saturate(180%) blur(18px);
}

.site-nav-inner {
    display: flex;
    align-items: center;
    gap: 16px;
    height: 100%;
}

.site-brand {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    color: var(--text);
    font-weight: 800;
    font-size: 1.05rem;
    letter-spacing: -0.02em;
    white-space: nowrap;
}
.site-brand:hover { color: var(--text); }
.site-brand-avatar {
    width: 32px;
    height: 32px;
    border-radius: 10px;
    object-fit: cover;
    box-shadow: 0 0 0 2px var(--surface), 0 0 0 3px var(--accent-ring);
}

.navbar-collapse {
    display: flex;
    flex: 1;
    justify-content: center;
    flex-basis: auto;
}
.mobile-menu-head { display: none; }
.site-menu {
    display: flex;
    align-items: center;
    gap: 2px;
    margin: 0;
    padding: 4px;
    list-style: none;
    border-radius: var(--radius-pill);
}
.site-menu .nav-link {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 8px 12px;
    border-radius: var(--radius-pill);
    color: var(--text-2);
    font-size: 0.9rem;
    font-weight: 500;
    white-space: nowrap;
    transition: color .2s ease, background-color .2s ease;
}
.site-menu .nav-link i { display: none; }
.site-menu .nav-link:hover { color: var(--text); background: var(--accent-soft); }
.site-menu .nav-link.active { color: var(--accent); background: var(--accent-soft); }

.site-nav-actions { display: flex; align-items: center; gap: 8px; margin-left: auto; }

/* EN / VI segmented toggle */
.lang-toggle { position: relative; }
.language-switch-label {
    position: relative;
    display: inline-flex;
    align-items: center;
    height: 40px;
    padding: 4px;
    margin: 0;
    border-radius: 12px;
    border: 1px solid var(--border);
    background: var(--surface);
    cursor: pointer;
    user-select: none;
}
.lang-opt {
    position: relative;
    z-index: 1;
    display: grid;
    place-items: center;
    width: 34px;
    height: 30px;
    border-radius: 8px;
    color: var(--muted);
    font-size: 0.78rem;
    font-weight: 700;
    letter-spacing: .03em;
    transition: color .25s ease, background-color .25s ease;
}
.lang-switch-input:not(:checked) + .language-switch-label .lang-opt--en,
.lang-switch-input:checked + .language-switch-label .lang-opt--vi {
    background: var(--text);
    color: var(--bg);
}
.lang-switch-input:focus-visible + .language-switch-label { outline: 2px solid var(--accent); outline-offset: 2px; }

/* theme toggle icons */
.theme-toggle .theme-icon-light { display: none; }
[data-theme="dark"] .theme-toggle .theme-icon-light { display: inline-block; }
[data-theme="dark"] .theme-toggle .theme-icon-dark { display: none; }
.theme-toggle i { transition: transform .4s var(--ease); }
.theme-toggle:hover i { transform: rotate(-20deg); }

/* hamburger */
.navbar-toggler { display: none; padding: 0; box-shadow: none !important; }
.toggler-lines { position: relative; display: block; width: 18px; height: 12px; }
.toggler-lines span {
    position: absolute;
    left: 0;
    width: 100%;
    height: 2px;
    border-radius: 2px;
    background: currentColor;
    transition: transform .3s var(--ease), top .3s var(--ease);
}
.toggler-lines span:nth-child(1) { top: 2px; }
.toggler-lines span:nth-child(2) { top: 8px; }
.navbar-toggler[aria-expanded="true"] .toggler-lines span:nth-child(1) { top: 5px; transform: rotate(45deg); }
.navbar-toggler[aria-expanded="true"] .toggler-lines span:nth-child(2) { top: 5px; transform: rotate(-45deg); }

.navbar-backdrop { display: none; }

@media (max-width: 1199.98px) {
    .site-menu .nav-link { padding: 8px 9px; font-size: 0.86rem; }
}

@media (max-width: 991.98px) {
    .navbar-toggler { display: inline-grid; }

    .navbar-backdrop {
        display: block;
        position: fixed;
        inset: var(--header-h) 0 0 0;
        background: rgba(2, 6, 23, 0.35);
        opacity: 0;
        pointer-events: none;
        transition: opacity .3s ease;
    }
    .navbar-backdrop.is-open { opacity: 1; pointer-events: auto; }

    .navbar-collapse {
        position: fixed;
        top: calc(var(--header-h) + 8px);
        left: 12px;
        right: 12px;
        display: block;
        padding: 12px;
        background: var(--surface);
        border: 1px solid var(--border);
        border-radius: var(--radius-lg);
        box-shadow: var(--shadow-lg);
        opacity: 0;
        visibility: hidden;
        transform: translateY(-8px) scale(.98);
        transform-origin: top center;
        transition: opacity .25s ease, transform .3s var(--ease), visibility 0s linear .3s;
    }
    .navbar-collapse.show {
        opacity: 1;
        visibility: visible;
        transform: none;
        transition: opacity .25s ease, transform .3s var(--ease), visibility 0s;
    }
    .mobile-menu-head {
        display: block;
        padding: 6px 12px 10px;
    }
    .mobile-menu-eyebrow {
        color: var(--muted);
        font-size: 0.72rem;
        font-weight: 700;
        letter-spacing: .1em;
        text-transform: uppercase;
    }
    .site-menu { flex-direction: column; align-items: stretch; gap: 2px; padding: 0; }
    .site-menu .nav-link {
        display: flex;
        padding: 12px 14px;
        border-radius: 12px;
        font-size: 1rem;
    }
    .site-menu .nav-link i { display: inline-block; width: 20px; color: var(--accent); }
    body.nav-open { overflow: hidden; }
}

@media (max-width: 359.98px) {
    .site-brand-name { display: none; }
}