:root {
  --primary-color: #2b5fab;
  --background-light: #f6f7f9;
  --text-color: #222;
  --text-muted: #666;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 2rem;
  --border-radius: 4px;
  --font-base: 16px;
  --transition-fast: 0.2s ease-in-out;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
  background-color: var(--background-light);
  color: var(--text-color);
  font-size: var(--font-base);
}

/* ================================ */
/* Filter and Chart Layout */
/* ================================ */

.filter-panel {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
  align-items: center;
  padding: var(--spacing-md);
  background-color: #fff;
  border-radius: var(--border-radius);
  box-shadow: 0 1px 3px rgba(0,0,0,0.1);
  margin-bottom: var(--spacing-md);
}

.chart-panel {
  background-color: #fff;
  border-radius: var(--border-radius);
  box-shadow: 0 1px 3px rgba(0,0,0,0.1);
  padding: var(--spacing-lg);
  display: flex;
  flex-direction: column;
  min-height: 300px;
  transition: box-shadow var(--transition-fast);
}

.chart-panel:hover {
  box-shadow: 0 2px 6px rgba(0,0,0,0.15);
}

@media (min-width: 768px) {
  .layout-container {
    display: grid;
    grid-template-columns: 300px 1fr;
    gap: var(--spacing-md);
  }
  .filter-panel {
    flex-direction: column;
  }
}

/* ================================ */
/* Summary Metrics */
/* ================================ */

.summary-metrics {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-around;
  background-color: #fff;
  border-radius: var(--border-radius);
  padding: var(--spacing-md);
  box-shadow: 0 1px 3px rgba(0,0,0,0.1);
  margin-bottom: var(--spacing-md);
}

.summary-metrics__item {
  text-align: center;
  margin: var(--spacing-sm);
}

.summary-metrics__label {
  display: block;
  color: var(--text-muted);
  font-size: 0.875rem;
  margin-bottom: var(--spacing-sm);
}

.summary-metrics__value {
  font-size: 1.5rem;
  font-weight: bold;
  color: var(--primary-color);
}

@media (min-width: 1024px) {
  .summary-metrics__value {
    font-size: 2rem;
  }
}

/* ================================ */
/* Accessibility Enhancements */
/* ================================ */

.filter-panel button:focus,
.chart-panel button:focus,
.summary-metrics__item:focus-within {
  outline: 2px solid var(--primary-color);
  outline-offset: 2px;
}

/* ================================ */
/* Footer */
/* ================================ */

footer {
  text-align: center;
  font-size: 0.875rem;
  color: var(--text-muted);
  padding: var(--spacing-md);
}

footer::after {
  content: "© 2026 Donau2Space.de";
  display: block;
  margin-top: var(--spacing-sm);
}