body {
  font-family: 'Arial', sans-serif;
  background-color: #f4f4f9;
  color: #333;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
}

.container {
  text-align: center;
  background: #fff;
  padding: 20px;
  border-radius: 10px;
  box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

h1 {
  color: #4CAF50;
}

#sudoku-grid {
  display: grid;
  grid-template-columns: repeat(9, 50px);
  grid-template-rows: repeat(9, 50px);
  gap: 2px;
  margin: 20px auto;
}

#sudoku-grid input {
  width: 50px;
  height: 50px;
  text-align: center;
  font-size: 18px;
  border: 1px solid #ccc;
  border-radius: 5px;
  color: #111;
  font-weight: bold;
}

#sudoku-grid input:focus {
  outline: none;
  border-color: #4CAF50;
  color: #111;
  font-weight: bold;
}

button {
  padding: 10px 20px;
  font-size: 16px;
  color: #fff;
  background-color: #4CAF50;
  border: none;
  border-radius: 5px;
  cursor: pointer;
  margin: 10px;
}

button:hover {
  background-color: #45a049;
}

button#clear-btn {
  background-color: #f44336;
}

button#clear-btn:hover {
  background-color: #e53935;
}