header {
    width: 100%;
}

/* Toggle button */
.menu-toggle {
    position: fixed;
    top: 0.6rem;
    left: 0.6rem;
    z-index: 120;
    width: 2.4rem;
    height: 2.4rem;
    border-radius: 50%;
    border: none;
    display: none;
    align-items: center;
    justify-content: center;
    background: var(--primary-color);
    color: var(--on-primary-color);
    box-shadow: 0 2px 10px rgba(0,0,0,0.15);
}

.backdrop {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.35);
    z-index: 90;
    opacity: 0;
    pointer-events: none;
    transition: opacity .2s ease;
}
.backdrop.show {
    opacity: 1;
    pointer-events: auto;
}

header nav {
    display: flex;
    width: 100%;
    padding: 0.3rem 0.8rem;
    background-color: var(--primary-color);
    align-items: center;
    justify-content: space-around;
    position: fixed;
    left: 0;
    right: 0;
    bottom: 0;
    z-index: 99;
    transform: translateY(0);
}

header nav.active { bottom: 0; }

header nav.scroll { transform: translateY(100%); }

header nav a {
    display: flex;
    align-items: center;
    justify-content: center;
    flex-direction: column;
    gap: 0.1rem;
    width: 4rem;
    height: 3rem;
    color: var(--on-primary-color);
}

header nav a i {
    font-size: 1.2rem;
}

header nav a span {
    font-size: 0.65rem;
}

header nav a:hover { opacity: 0.9; }

/* Responsive: mobile sidebar */
@media screen and (max-width: 768px) {
    .menu-toggle { display: inline-flex; }
    header nav {
        top: 0;
        bottom: auto;
        right: auto;
        width: 76vw;
        max-width: 320px;
        height: 100vh;
        flex-direction: column;
        justify-content: flex-start;
        padding: 4rem 1rem 1rem;
        transform: translateX(-100%);
        transition: transform .25s ease;
    }
    header nav.active { transform: translateX(0); }
    header nav.scroll { transform: translateX(-100%); }
    header nav a { width: 100%; height: 3.2rem; flex-direction: row; gap: 0.6rem; justify-content: flex-start; }
    header nav a i { font-size: 1.3rem; }
}

/* Desktop/tablet bottom bar */
@media screen and (min-width: 769px) {
    .menu-toggle { display: none; }
    .backdrop { display: none; }
}