/* --- Navigation (Top App Bar) --- */
header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--nav-height, 72px);
    background-color: rgba(254, 247, 255, 0.9);
    backdrop-filter: blur(10px);
    z-index: 1000;
    border-bottom: 1px solid rgba(0, 0, 0, 0.05);
    display: flex;
    justify-content: center;
}

.nav-content {
    display: flex;
    align-items: center;
    justify-content: space-between;
    width: 100%;
    max-width: 1200px;
    padding: 0 24px;
    height: 100%;
}

.logo {
    font-family: 'IBM Plex Sans', sans-serif;
    font-weight: 700;
    font-size: 25px;
    color: var(--md-sys-color-primary, #6750A4);
    text-decoration: none;
}

nav ul {
    display: flex;
    gap: 8px;
    list-style: none;
    margin: 0;
    padding: 0;
}

nav a {
    text-decoration: none;
    color: var(--md-sys-color-on-surface-variant, #49454F);
    padding: 10px 16px;
    border-radius: 20px;
    font-weight: 500;
    font-size: 19px;
    transition: background 0.2s;
}

nav a:hover,
nav a.active {
    background-color: var(--md-sys-color-surface-container-high, #ECE6F0);
    color: var(--md-sys-color-on-surface, #1D1B20);
}

/* Mobile Menu Hidden by default on desktop */
.mobile-toggle {
    display: none;
}

@media (max-width: 768px) {
    nav ul {
        display: none;
    }

    /* Hide standard nav */
    .mobile-toggle {
        display: block;
        background: none;
        border: none;
        cursor: pointer;
        color: var(--md-sys-color-on-surface, #1D1B20);
    }

    /* Mobile Menu State */
    nav.open ul {
        display: flex;
        flex-direction: column;
        position: absolute;
        top: var(--nav-height, 72px);
        left: 0;
        right: 0;
        background: var(--md-sys-color-surface, #FEF7FF);
        padding: 24px;
        box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
        border-bottom-left-radius: 24px;
        border-bottom-right-radius: 24px;
        z-index: 1001;
    }
}