/* =========================================================
   app.css — Page-level layout (header, footer, etc.)
   ========================================================= */

/* ---------- Header ---------- */
.site-header {
    position: sticky;
    top: 0;
    z-index: 100;
    background-color: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    backdrop-filter: saturate(180%) blur(8px);
    transition: background-color var(--transition-base);
}
.site-header .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: var(--header-height);
    gap: var(--space-4);
}

.brand {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    font-weight: 700;
    font-size: var(--font-size-lg);
    color: var(--color-text);
    text-decoration: none;
}
.brand-logo {
    width: 32px;
    height: 32px;
    background: linear-gradient(135deg,
        var(--color-primary) 0%,
        var(--color-accent) 100%);
    border-radius: var(--radius-sm);
    display: grid;
    place-items: center;
    color: #fff;
    font-size: 1rem;
}

/* ---------- Primary navigation ---------- */
.main-nav {
    display: none;
    align-items: center;
    gap: var(--space-5);
}
.main-nav a {
    color: var(--color-text-muted);
    font-weight: 500;
    transition: color var(--transition-fast);
}
.main-nav a:hover,
.main-nav a.active {
    color: var(--color-primary);
}

@media (min-width: 900px) {
    .main-nav { display: flex; }
}

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

/* ---------- Theme toggle button ---------- */
.theme-toggle {
    width: 40px;
    height: 40px;
    border-radius: var(--radius-pill);
    display: grid;
    place-items: center;
    background: var(--color-surface-2);
    border: 1px solid var(--color-border);
    cursor: pointer;
    color: var(--color-text);
    transition: background-color var(--transition-fast), transform var(--transition-fast);
}
.theme-toggle:hover {
    background-color: var(--color-primary-soft);
    color: var(--color-primary);
}
.theme-toggle svg {
    width: 20px;
    height: 20px;
}

[data-theme="light"] .theme-toggle .icon-sun  { display: none; }
[data-theme="dark"]  .theme-toggle .icon-moon { display: none; }

/* ---------- Mobile nav (hamburger) ---------- */
.mobile-nav-toggle {
    display: grid;
    place-items: center;
    width: 40px;
    height: 40px;
    background: transparent;
    border: none;
    cursor: pointer;
    color: var(--color-text);
}
@media (min-width: 900px) {
    .mobile-nav-toggle { display: none; }
}

.mobile-nav {
    display: none;
    border-top: 1px solid var(--color-border);
    background-color: var(--color-surface);
    padding: var(--space-3) 0;
}
.mobile-nav.open { display: block; }
.mobile-nav a {
    display: block;
    padding: var(--space-3) var(--space-4);
    color: var(--color-text);
    font-weight: 500;
}
.mobile-nav a:hover {
    background-color: var(--color-surface-2);
    color: var(--color-primary);
}

/* ---------- Footer ---------- */
.site-footer {
    background-color: var(--color-surface);
    border-top: 1px solid var(--color-border);
    padding: var(--space-7) 0 var(--space-5);
    margin-top: var(--space-8);
    color: var(--color-text-muted);
}
.site-footer-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: var(--space-5);
    margin-bottom: var(--space-5);
}
@media (min-width: 700px) {
    .site-footer-grid {
        grid-template-columns: 2fr 1fr 1fr;
    }
}
.site-footer h4 {
    font-size: 1rem;
    color: var(--color-text);
    margin-bottom: var(--space-3);
}
.site-footer a {
    color: var(--color-text-muted);
}
.site-footer a:hover {
    color: var(--color-primary);
}
.site-footer-bottom {
    padding-top: var(--space-4);
    border-top: 1px solid var(--color-border);
    text-align: center;
    font-size: var(--font-size-sm);
}

/* ---------- Utilities ---------- */
.text-center { text-align: center; }
.mt-4 { margin-top: var(--space-4); }
.mb-4 { margin-bottom: var(--space-4); }
.mb-5 { margin-bottom: var(--space-5); }
.mb-6 { margin-bottom: var(--space-6); }