html,
body,
* {
  -webkit-user-select: none;
  user-select: none;
}

#grid {
  font-family: 'Gill Sans', 'Gill Sans MT', Calibri, 'Trebuchet MS', sans-serif;
  font-size: 12pt;
  text-align: center;
}

#grid td {
  width: 20px;
  height: 20px;
  border: 1px solid #828282;
  background-color: #c3c3c3;
  cursor: pointer;
}

#grid td.covered {
  color: transparent;
  background-color: #828282;
}

#grid td.flagged {
  color: transparent;
  background-color: #800000;
}

#grid td[data-value="0"] {
  color: transparent;
}

#grid td.visible[data-value="9"] {
  color: transparent;
  background-color: #f00;
}