body {
  background-color: #bb6;
  text-align: center;
  color: #335;
  user-select: none;
}

.row {
  height: 10%;
}

.cell {
  cursor: pointer;
  display: inline-block;
  width: 10%;
  height: 10%;
  margin: 5px;
  background-color: #dde;
  border-color: #dde;
  border-style: solid;
  border-radius: 15px;
}

.cell.empty {
  visibility:hidden;
}

.cell:not(.counted):hover {
  background-color: #888;
  border-color: #666;
  transform: rotate(-2deg);
}

.cell.counted {
  background-color: #77a;
  border-color: #77a;
  border-style: solid;
}

.cell.counted:hover {
  background-color: #557;
  border-color: #557;
  transform: rotate(-2deg);
}

.button {
  font-size: 50px;
  padding: 8px 16px;
  margin: 8px;
  background-color: #2cc;
  border-radius: 12px;
  border-color: #666;
  border-style: solid;
}

.button:hover {
  background-color: #377;
}

.button.wrong {
  background-color: #f77;
}

.button.wrong:hover {
background: repeating-linear-gradient(
  45deg,
  #f77,
  #f77 10px,
  #a88 10px,
  #a88 20px
);
}