.nav-header {
    display: none;
    position: sticky;
    top: 0;
    z-index: 100;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    padding: 8px 16px;
    justify-content: space-between;
    align-items: center;
}

.nav-watermark {
    font-family: 'Heraldic', serif;
    margin-top: 2px;
    font-size: 32px;
    color: #FFFFFF;
    user-select: none;
    pointer-events: none;
    line-height: 1;
}

.nav-toggle {
    display: flex;
    background: transparent;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 8px 10px;
    cursor: pointer;
    flex-direction: column;
    gap: 4px;
    align-items: center;
    justify-content: center;
    margin-left: auto;
}

.hamburger-line {
    display: block;
    width: 20px;
    height: 2px;
    background: var(--fg);
    border-radius: 1px;
}

.nav-pane {
    display: flex;
    justify-content: center;
    gap: 8px;
    position: sticky;
    top: 0;
    z-index: 100;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.5);
    padding: 12px 16px;
}

.tab-btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    background: var(--bg-surface);
    color: var(--fg);
    border: 1px solid var(--border-light);
    border-radius: var(--radius);
    padding: 10px 24px;
    cursor: pointer;
    font-family: inherit;
    text-transform: uppercase;
    letter-spacing: 1px;
    text-decoration: none;
}

.tab-btn:hover {
    background: var(--border-light);
    color: var(--fg);
    border-color: var(--fg-muted);
}

.tab-btn.active {
    background: var(--fg);
    color: var(--bg);
    border-color: var(--fg);
}

.tab-icon {
    padding-top: 5px;
}

.tab-icon-filled {
    padding-top: 5px;
}

.tab-btn .tab-icon-filled {
    display: none;
}

.tab-btn:is(.active, :hover) .tab-icon {
    display: none;
}

.tab-btn:is(.active, :hover) .tab-icon-filled {
    display: inline-block;
}

@media (max-width: 640px) {
    .nav-header {
        display: flex;
    }

    .nav-pane {
        display: none;
        position: fixed;
        top: 48px;
        left: 0;
        right: 0;
        flex-direction: column;
        background: var(--bg);
        border: 1px solid var(--border);
        border-top: none;
        box-shadow: 0 8px 24px rgba(0, 0, 0, 0.6);
        padding: 6px 16px 12px;
        gap: 0;
    }

    .nav-pane.is-open,
    .nav-pane.article-back {
        display: flex;
    }

    .nav-pane.article-back {
        position: sticky;
        top: 0;
        flex-direction: row;
        padding: 12px 16px;
        border: none;
        border-bottom: 1px solid var(--border);
        box-shadow: 0 2px 8px rgba(0, 0, 0, 0.5);
    }

    .tab-btn {
        width: 100%;
        text-align: left;
        margin-bottom: 6px;
    }

    .tab-btn:last-child {
        margin-bottom: 0;
    }
}

@media print {
    .nav-header,
    .nav-pane,
    .nav-toggle,
    .nav-watermark {
        display: none;
    }
}