button.phet-button.disabled {
  color: #bbb;
  background-color: #eee;
}

button.phet-button.disabled:hover {
  background-color: #eee;
  cursor: default;
}

button.phet-button {
  text-align: center;
  padding: 10px;
  border-radius: 5px;
  border: none;
  display: block;
  background-color: cornflowerblue;
  color: white;
  font-size: 16px;
  font-weight: bold;
}

button.phet-button:hover {
  background: lightskyblue;
  cursor: pointer;
}