.top-header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--header-height);
    background: linear-gradient(135deg, #1e293b 0%, #0f172a 100%);
    display: flex;
    align-items: center;
    padding: 0 var(--spacing-lg);
    z-index: 1000;
    box-shadow: var(--shadow-md);
}

.header-left {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    color: var(--text-white);
    flex-shrink: 0;
}

.header-logo {
    display: flex;
    align-items: center;
    opacity: 0.9;
}

.header-title {
    font-size: 17px;
    font-weight: 600;
    letter-spacing: 0.5px;
    white-space: nowrap;
}

.header-nav {
    display: flex;
    align-items: center;
    gap: 2px;
    margin-left: var(--spacing-xl);
    flex: 1;
    overflow-x: auto;
}

.header-nav .nav-item {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    font-size: 14px;
    font-weight: 500;
    color: rgba(255,255,255,0.7);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition-fast);
    white-space: nowrap;
    border: none;
    background: none;
}
.header-nav .nav-item:hover { color: var(--text-white); background: rgba(255,255,255,0.08); }
.header-nav .nav-item.active { color: var(--text-white); background: rgba(255,255,255,0.12); }

.header-right {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    flex-shrink: 0;
}

.header-user {
    font-size: 13px;
    color: rgba(255,255,255,0.8);
}

.main-content {
    position: fixed;
    top: var(--header-height);
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--bg-body);
}

#mainFrame {
    width: 100%;
    height: 100%;
    border: none;
    display: block;
}