/* ==========================================================================
   Header, navigation, theme toggle. Mobile-first: hamburger panel below
   1024px, full inline nav above.
   ========================================================================== */

.site-header {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: var(--header-height);
    background-color: var(--header-bg);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid transparent;
    z-index: 1000;
    transition: background-color var(--dur-base) ease, border-color var(--dur-base) ease, box-shadow var(--dur-base) ease;
}

.site-header.scrolled {
    border-bottom-color: var(--border-color);
    box-shadow: var(--shadow-1);
}

.header-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: var(--space-4);
    height: 100%;
}

.logo {
    font-family: var(--font-heading);
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--heading-color);
    letter-spacing: -0.02em;
    white-space: nowrap;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: var(--space-2);
}

/* ── Theme toggle ─────────────────────────────────────────────────────── */
.theme-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 44px;
    height: 44px;
    border: none;
    border-radius: var(--radius-full);
    background: transparent;
    color: var(--header-text);
    transition: background-color var(--dur-fast) ease, color var(--dur-fast) ease;
}

.theme-toggle:hover {
    background: var(--highlight-bg);
    color: var(--primary-color);
}

.theme-toggle svg { width: 20px; height: 20px; }

/* Show the icon for the theme you'd switch TO */
.theme-toggle .icon-sun { display: none; }
.theme-toggle .icon-moon { display: block; }
[data-theme="dark"] .theme-toggle .icon-sun { display: block; }
[data-theme="dark"] .theme-toggle .icon-moon { display: none; }

/* ── Hamburger button ─────────────────────────────────────────────────── */
.menu-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 44px;
    height: 44px;
    background: transparent;
    border: none;
    border-radius: var(--radius-full);
    color: var(--header-text);
    font-size: 1.25rem;
    transition: background-color var(--dur-fast) ease, color var(--dur-fast) ease;
}

.menu-toggle:hover {
    background: var(--highlight-bg);
    color: var(--primary-color);
}

/* ── Mobile nav panel (default, <1024px) ──────────────────────────────── */
.main-nav {
    position: fixed;
    top: var(--header-height);
    right: 0;
    width: min(320px, 85vw);
    height: calc(100dvh - var(--header-height));
    background: var(--surface-color);
    border-left: 1px solid var(--border-color);
    box-shadow: var(--shadow-3);
    padding: var(--space-6) var(--space-4);
    overflow-y: auto;
    transform: translateX(100%);
    visibility: hidden;
    transition: transform var(--dur-base) var(--ease-out), visibility var(--dur-base);
}

.main-nav.active {
    transform: translateX(0);
    visibility: visible;
}

.main-nav ul {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: var(--space-1);
}

.main-nav li { margin: 0; }

.main-nav a {
    display: block;
    padding: var(--space-3) var(--space-4);
    border-radius: var(--radius-sm);
    color: var(--text-color);
    font-weight: 500;
    min-height: 44px;
    transition: background-color var(--dur-fast) ease, color var(--dur-fast) ease;
}

.main-nav a:hover,
.main-nav a.active {
    background: var(--highlight-bg);
    color: var(--primary-color);
}

/* Dropdown — mobile: inline expandable sub-list */
.nav-dropdown-toggle i {
    font-size: 0.7em;
    margin-left: var(--space-1);
    transition: transform var(--dur-fast) ease;
}

.nav-dropdown.dropdown-open .nav-dropdown-toggle i {
    transform: rotate(180deg);
}

.dropdown-menu {
    list-style: none;
    display: none;
    padding-left: var(--space-4);
}

.nav-dropdown.dropdown-open .dropdown-menu {
    display: flex;
    flex-direction: column;
    gap: var(--space-1);
}

/* ── Desktop nav (≥1024px) ────────────────────────────────────────────── */
@media (min-width: 1024px) {
    .menu-toggle { display: none; }

    .main-nav {
        position: static;
        width: auto;
        height: auto;
        background: transparent;
        border: none;
        box-shadow: none;
        padding: 0;
        overflow: visible;
        transform: none;
        visibility: visible;
        transition: none;
    }

    .main-nav ul {
        flex-direction: row;
        align-items: center;
        gap: var(--space-2);
    }

    .main-nav a {
        padding: var(--space-2) var(--space-3);
        font-size: 0.95rem;
        white-space: nowrap;
    }

    /* Dropdown — desktop: hover/focus floating panel.
       .main-nav selector prefix needed to beat `.main-nav ul` row direction. */
    .nav-dropdown { position: relative; }

    .main-nav .dropdown-menu {
        display: flex;
        flex-direction: column;
        position: absolute;
        top: calc(100% + 0.4rem);
        right: 0;
        min-width: 180px;
        background: var(--surface-color);
        border: 1px solid var(--border-color);
        border-radius: var(--radius-md);
        box-shadow: var(--shadow-2);
        padding: var(--space-2);
        opacity: 0;
        visibility: hidden;
        pointer-events: none;
        transform: translateY(4px);
        transition: opacity var(--dur-fast) ease, transform var(--dur-fast) ease, visibility var(--dur-fast);
        z-index: 200;
    }

    .nav-dropdown:hover .dropdown-menu,
    .nav-dropdown:focus-within .dropdown-menu,
    .nav-dropdown.dropdown-open .dropdown-menu {
        opacity: 1;
        visibility: visible;
        pointer-events: auto;
        transform: translateY(0);
    }
}