tictactoe.css

html {
  font-family: sans-serif;
}
body {
  margin: 0;
}
h1{
  margin-top:30px;
  text-align:center;
}
#board{
  margin:50px auto 20px auto;
  width:360px;
}
.cell{
  background-color:#efefef;
  height:100px;
  width:100px;
  margin:10px;
  font-size:30px;
}