body {
  font-family: Arial, sans-serif;
  margin: 0;
  padding: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  background-color: #f4f4f9;
}

.container {
  text-align: center;
}

h1 {
  margin-bottom: 20px;
}

.game-board {
  display: grid;
  grid-template-columns: repeat(6, 60px);
  grid-gap: 5px;
  justify-content: center;
  margin-bottom: 20px;
}

.cell {
  width: 60px;
  height: 60px;
  text-align: center;
  font-size: 24px;
  border: 1px solid #ccc;
  display: flex;
  justify-content: center;
  align-items: center;
  background-color: white;
}

.fixed {
  background-color: #f0f0f0;
}

.solved {
  background-color: #d4f7d4; /* Light green for solved cells */
}

.controls {
  margin-bottom: 20px;
}

#restart-btn, #show-solution-btn {
  padding: 10px 20px;
  margin-top: 10px;
  background-color: #4CAF50;
  color: white;
  border: none;
  cursor: pointer;
}

#restart-btn:hover, #show-solution-btn:hover {
  background-color: #45a049;
}

.numpad {
  display: flex;
  justify-content: center;
  gap: 10px;
}

.numpad-btn {
  padding: 15px;
  font-size: 18px;
  cursor: pointer;
  background-color: #ddd;
  border: none;
  border-radius: 5px;
}

.numpad-btn:hover {
  background-color: #ccc;
}