:root {
  --color-bg-header: #1e1e2f;
  --color-bg-main: #f6f7fb;
  --color-bg-filter: #ffffff;
  --color-border: #d1d1d1;
  --color-text: #222222;
  --color-accent: #4a90e2;
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 2rem;
  --font-base: 'Segoe UI', sans-serif;
  --font-size-sm: 0.875rem;
  --font-size-md: 1rem;
  --font-size-lg: 1.25rem;
  --footer-height: 3rem;
}

/* ------------------------------------------------------------- */
/* Header Styles */
/* ------------------------------------------------------------- */
.app-header {
  background-color: var(--color-bg-header);
  color: #ffffff;
  padding: var(--spacing-md);
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-family: var(--font-base);
}

.header-bar {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  font-size: var(--font-size-lg);
  font-weight: 500;
}

/* ------------------------------------------------------------- */
/* Chart Container */
/* ------------------------------------------------------------- */
.visualization-container {
  background-color: var(--color-bg-main);
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  width: 100%;
  height: calc(100vh - var(--footer-height) - 120px);
  padding: var(--spacing-md);
  box-sizing: border-box;
}

.chart-canvas {
  width: 100%;
  max-width: 960px;
  height: 60vh;
  background-color: #fff;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  box-shadow: 0 2px 4px rgba(0,0,0,0.08);
}

/* ------------------------------------------------------------- */
/* Filter Styles */
/* ------------------------------------------------------------- */
.filter-panel {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
  margin-bottom: var(--spacing-md);
  background-color: var(--color-bg-filter);
  padding: var(--spacing-md);
  border: 1px solid var(--color-border);
  border-radius: 6px;
}

.filter-panel label, .filter-panel select, .filter-panel input[type="checkbox"] {
  font-size: var(--font-size-md);
  color: var(--color-text);
}

.filter-panel select {
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: 4px;
  border: 1px solid var(--color-border);
  background-color: #fff;
}

.filter-panel input[type="checkbox"]:checked + label {
  color: var(--color-accent);
  font-weight: 500;
}

/* ------------------------------------------------------------- */
/* Footer Styles */
/* ------------------------------------------------------------- */
.app-footer {
  background-color: var(--color-bg-header);
  color: #ffffff;
  text-align: center;
  padding: var(--spacing-sm);
  font-size: var(--font-size-sm);
  font-family: var(--font-base);
}

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

/* ------------------------------------------------------------- */
/* Responsive Adjustments */
/* ------------------------------------------------------------- */
@media (min-width: 640px) {
  .filter-panel {
    justify-content: space-between;
  }
}

@media (min-width: 1024px) {
  .chart-canvas {
    height: 70vh;
  }
}