:root {
  --primary-color: #2196F3;
  --secondary-color: #1976D2;
  --background-color: #f5f5f5;
  --card-background: #ffffff;
  --text-color: #333333;
  --border-radius: 8px;
  --spacing: 20px;
}

* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

body {
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background-color: var(--background-color);
  color: var(--text-color);
  line-height: 1.6;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: var(--spacing);
}

header {
  text-align: center;
  margin-bottom: 2rem;
}

h1 {
  color: var(--primary-color);
  margin-bottom: 1rem;
}

section {
  background: var(--card-background);
  border-radius: var(--border-radius);
  padding: var(--spacing);
  margin-bottom: var(--spacing);
  box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

.info-grid, .dns-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing);
  margin-top: var(--spacing);
}

.info-card, .dns-card {
  background: var(--card-background);
  padding: var(--spacing);
  border-radius: var(--border-radius);
  box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}

button {
  background-color: var(--primary-color);
  color: white;
  border: none;
  padding: 10px 20px;
  border-radius: var(--border-radius);
  cursor: pointer;
  transition: background-color 0.3s;
}

button:hover {
  background-color: var(--secondary-color);
}

.mtu-controls {
  margin-bottom: var(--spacing);
}

.mtu-slider {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 1rem;
}

input[type="range"] {
  flex: 1;
}

.speed-results {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--spacing);
  margin-top: var(--spacing);
}

.result-card {
  text-align: center;
  padding: var(--spacing);
  background: var(--card-background);
  border-radius: var(--border-radius);
  box-shadow: 0 2px 4px rgba(0,0,0,0.05);
}

#mtu-results {
  margin-top: 1rem;
  padding: 1rem;
  background: #f8f9fa;
  border-radius: var(--border-radius);
}

.dns-card {
  text-align: center;
}

.dns-card button {
  margin-top: 1rem;
}

@media (max-width: 768px) {
  .info-grid, .dns-grid, .speed-results {
    grid-template-columns: 1fr;
  }
}