body {
  font-family: Arial, Helvitica, sans-serif;
  text-align: center;
}

#board {
  height: 540px;
  width: 630px;
  
  background-color: blue;
  border: 10px solid navy;
  
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
}

.tile {
    height: 90px;
    width: 90px;
    
    background-color: white;
    border-radius: 50%
}