#calendar {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px;
}

#calendar table {
  border-collapse: collapse;
  width: 100%;
  margin-bottom: 1em;
}

#calendar th,
#calendar td {
  border: 1px solid #ccc;
  padding: 4px;
  text-align: center;
  cursor: pointer;
}

#calendar td.holiday {
  background-color: #ffdddd;
  color: #900;
  font-weight: bold;
}