/* ==========================================
   4. HEADER / NAVIGATION
   ========================================== */
.site-header {
    position: sticky;
    top: 0;
    z-index: 1000;
    height: var(--header-height);
    background-color: var(--card-bg);
    border-bottom: 1px solid var(--border-color);
    transition: background-color var(--transition), border-color var(--transition);
}

.header-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 100%;
}

.site-branding {
    display: flex;
    align-items: center;
}

.custom-logo-link {
    display: inline-block;
    transition: opacity var(--transition-fast);
}

.custom-logo-link:hover {
    opacity: 0.8;
}

.custom-logo-link img {
    max-height: 48px;
    width: auto;
    display: block;
    border-radius: 0;
}

.custom-logo-link+.site-title {
    margin-left: 0.75rem;
}

/* Light/Dark Theme Specific Logo Display */
.custom-logo-link .logo-light,
.custom-logo-link .logo-dark {
    display: none !important;
}

body:not(.dark-mode) .custom-logo-link .logo-light {
    display: block !important;
}

body.dark-mode .custom-logo-link .logo-dark {
    display: block !important;
}

/* SVG Logo Color and Sizing Integration */
.custom-logo-link svg {
    max-height: 48px;
    width: auto;
    display: block;
}

.custom-logo-link .svg-logo-container {
    display: inline-block;
    vertical-align: middle;
}

.custom-logo-link .svg-logo-container svg {
    fill: var(--primary-color);
    transition: fill var(--transition);
}

.custom-logo-link .svg-logo-container svg [fill="none"] {
    fill: none;
}

.custom-logo-link .svg-logo-container svg [stroke] {
    stroke: var(--primary-color);
    transition: stroke var(--transition);
}

/* Deep selection for children shapes */
.custom-logo-link .svg-logo-container svg path,
.custom-logo-link .svg-logo-container svg circle,
.custom-logo-link .svg-logo-container svg rect,
.custom-logo-link .svg-logo-container svg polygon,
.custom-logo-link .svg-logo-container svg ellipse,
.custom-logo-link .svg-logo-container svg polyline,
.custom-logo-link .svg-logo-container svg line {
    transition: fill var(--transition), stroke var(--transition);
}

.custom-logo-link .svg-logo-container svg path:not([fill="none"]),
.custom-logo-link .svg-logo-container svg circle:not([fill="none"]),
.custom-logo-link .svg-logo-container svg rect:not([fill="none"]),
.custom-logo-link .svg-logo-container svg polygon:not([fill="none"]),
.custom-logo-link .svg-logo-container svg ellipse:not([fill="none"]),
.custom-logo-link .svg-logo-container svg polyline:not([fill="none"]),
.custom-logo-link .svg-logo-container svg line:not([fill="none"]) {
    fill: var(--primary-color);
}

.custom-logo-link .svg-logo-container svg path[stroke],
.custom-logo-link .svg-logo-container svg circle[stroke],
.custom-logo-link .svg-logo-container svg rect[stroke],
.custom-logo-link .svg-logo-container svg polygon[stroke],
.custom-logo-link .svg-logo-container svg ellipse[stroke],
.custom-logo-link .svg-logo-container svg polyline[stroke],
.custom-logo-link .svg-logo-container svg line[stroke] {
    stroke: var(--primary-color);
}

.site-title {
    font-size: var(--font-lg);
    font-weight: var(--weight-bold);
    margin-bottom: 0;
    color: var(--primary-color);
    transition: opacity var(--transition-fast);
}

.site-title:hover {
    opacity: 0.8;
}

.site-navigation {
    display: flex;
    align-items: center;
    gap: 1.5rem;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 1.5rem;
    align-items: center;
}

.nav-menu a {
    color: var(--text-color);
    font-weight: var(--weight-medium);
    position: relative;
    padding: 0.25rem 0;
}

.nav-menu a::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary-color);
    transition: width var(--transition);
}

.nav-menu a:hover::after,
.nav-menu .current-menu-item>a::after {
    width: 100%;
}

/* Toggle and Mode Buttons */
.header-actions {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.theme-toggle-btn {
    background: none;
    border: 1px solid var(--border-color);
    width: 40px;
    height: 40px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background-color var(--transition-fast), border-color var(--transition-fast);
    color: var(--text-color);
}

.theme-toggle-btn:hover {
    background-color: var(--border-color);
}

.theme-toggle-btn svg {
    width: 18px;
    height: 18px;
    fill: none;
    stroke: currentColor;
    stroke-width: 2;
    stroke-linecap: round;
    stroke-linejoin: round;
    transition: transform var(--transition);
}

.dark-mode-icon {
    display: none;
}

body.dark-mode .light-mode-icon {
    display: none;
}

body.dark-mode .dark-mode-icon {
    display: block;
}

/* Mobile Toggle Hamburger */
.menu-toggle {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0.5rem;
}

.menu-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background-color: var(--text-color);
    margin: 5px 0;
    transition: var(--transition-fast);
}

@media (max-width: 768px) {
    .menu-toggle {
        display: block;
    }

    .nav-menu {
        position: absolute;
        top: var(--header-height);
        left: 0;
        right: 0;
        background-color: var(--card-bg);
        border-bottom: 1px solid var(--border-color);
        flex-direction: column;
        padding: 1.5rem 0;
        gap: 1rem;
        transform: translateY(-150%);
        opacity: 0;
        transition: transform var(--transition), opacity var(--transition);
        box-shadow: var(--shadow-lg);
        z-index: 999;
    }

    .nav-menu.active {
        transform: translateY(0);
        opacity: 1;
    }
}