#controls {
  margin-bottom: 20px;
}

#sudoku-grid {
  display: inline-grid;
  grid-template-columns: repeat(9, 50px);
  grid-template-rows: repeat(9, 50px);
  gap: 1px;
}

.cell {
  width: 47px;
  height: 48px;
  font-size: 20px;
  text-align: center;
  line-height: 50px;
  border: 1px solid #ccc;
  cursor: pointer;
  background-color: transparent;
  padding: 1px;
}

.cell.read-only {
  background-color: #eee;
  cursor: default;
}

.cell.selected {
  background-color: #add8e6;
}

.cell.invalid {
  background-color: #f8d7da; /* Light red background */
}

#keypad {
  display: none;
  margin-top: 20px;
}

#keypad .key {
  display: inline-block;
  width: 50px;
  height: 50px;
  margin: 3px;
  line-height: 50px;
  background-color: #f1f1f1;
  cursor: pointer;
  user-select: none;
}

#keypad .key:hover {
  background-color: #ddd;
}

@media (hover: none) {
  #keypad {
    display: block;
  }
}

#timer {
  font-size: 20px;
  margin-bottom: 10px;
}

#message {
  font-size: 24px;
  color: green;
  margin-bottom: 10px;
}

#sudoku-grid.completed {
  animation: grid-complete 1s forwards;
}

@keyframes grid-complete {
  from { background-color: transparent; }
  to { background-color: #d4edda; } /* Light green background */
}