html, body {
  margin: 5;
  padding: 10px;
  display: flex;
  background: radial-gradient(circle, white 4px, transparent 4px);
  background-color: teal;
  background-size: 20px 20px;
  justify-content: center;
  align-items: center;
  min-height: 100ch;
 
  font-family: Arial, sans-serif; 
}

main {
  background: white;
  padding: 20px;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1); 
}

h1 {
  margin-top: 0;
}