body {
  font-family: 'Helvetica', sans-serif;
}

h1 {
  text-align: center;
}

#board {
  margin-left: auto;
  margin-right: auto;
  text-align: center;
}

#button {
  width: 8em;
  margin-left: auto;
  margin-right: auto;
  background-color: #ccc;
  padding: 1em; 
  font-weight: bold;
  border-radius: 0.5em;
  text-align: center;
}

#message {
  text-align: center;
}

.card {
  display: inline-block;
  margin-top: 0.5em;
  margin-left: 1em;

}

.card h4 {
  text-align: center;
  font-size: 0.75em;
}

.card .content {  
  font-size: 2em;
  font-weight: bold;
  padding-top: 2em;
  padding-bottom: 2em;
  padding-left: 0.2em;
  padding-right: 0.2em;
  border: 2px solid #000;
  border-radius: 0.5em;
  width: 3em;
  text-align: center;
}

#message {
  clear: both;
}

.red { 
  background-color: #f00;
}

.blue { 
  background-color: #00f;
}

.green { 
  background-color: #0f0;
}