:root {
    --surface-background: #ffffff;
    --surface-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    --surface-radius: 8px;
    --surface-padding: 20px;
    --accent-primary: #2a87ed;
    --muted-text: #666666;
    --border-subtle: #e9ecef;
}

.add-site-form,
.chart-card,
.data-section,
.stat-card {
    background: var(--surface-background);
    border-radius: var(--surface-radius);
    box-shadow: var(--surface-shadow);
    padding: var(--surface-padding);
}

/* Utility helper to hide elements while keeping layout hooks intact */
.is-hidden {
    display: none !important;
}