:root {
  --color-bg: #f9fafb;
  --color-surface: #ffffff;
  --color-primary: #2b6cb0;
  --color-accent: #3182ce;
  --color-border: #e2e8f0;
  --color-text: #1a202c;
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 2rem;
  --font-base: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --radius-sm: 4px;
  --radius-md: 6px;
  --max-width: 1200px;
}

/* =============================
   Header & Footer
   ============================= */
.app-header,
.app-footer {
  background-color: var(--color-surface);
  color: var(--color-text);
  padding: var(--spacing-md) var(--spacing-lg);
  border-bottom: 1px solid var(--color-border);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.app-header {
  position: sticky;
  top: 0;
  z-index: 1000;
}

.app-footer {
  border-top: 1px solid var(--color-border);
  border-bottom: none;
  justify-content: center;
  font-size: 0.9rem;
  text-align: center;
}

/* =============================
   Main Dashboard Layout
   ============================= */
.app-main {
  flex: 1;
  background-color: var(--color-bg);
  padding: var(--spacing-md);
  display: flex;
  flex-direction: column;
  align-items: center;
}

.metrics-dashboard {
  width: 100%;
  max-width: var(--max-width);
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-lg);
}

/* =============================
   Section Panels
   ============================= */
.charts-section,
.metrics-table {
  background-color: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--spacing-md);
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
}

.charts-section {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.metrics-table {
  overflow-x: auto;
}

/* =============================
   Filter Controls
   ============================= */
.filter-controls {
  display: flex;
  align-items: center;
  justify-content: flex-end;
  gap: var(--spacing-sm);
  margin-bottom: var(--spacing-md);
}

.filter-controls button {
  background-color: var(--color-primary);
  color: #fff;
  border: none;
  border-radius: var(--radius-sm);
  padding: var(--spacing-sm) var(--spacing-md);
  cursor: pointer;
  transition: background-color 0.2s ease;
}

.filter-controls button:hover,
.filter-controls button:focus {
  background-color: var(--color-accent);
}

.filter-controls button.active {
  background-color: var(--color-accent);
  font-weight: 600;
}

/* =============================
   Responsive Design
   ============================= */
@media (min-width: 640px) {
  .metrics-dashboard {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .metrics-dashboard {
    grid-template-columns: repeat(3, 1fr);
  }
}

/* =============================
   Accessibility Helpers
   ============================= */
:focus {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

/* =============================
   Footer Copyright
   ============================= */
.app-footer::after {
  content: '© 2026 Donau2Space.de';
  display: block;
  margin-top: var(--spacing-xs);
  color: var(--color-text);
}