header {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  background-color: #f8f9fa;
  padding: 12px;
  text-align: center;
  box-shadow: 0 2px 5px rgba(0,0,0,0.1);
  z-index: 1000;
  font-family: Arial, sans-serif;
}