body {
  font-family: Arial, sans-serif;
  display: flex;
  justify-content: center;
  align-items: center;
  height: 100vh;
  margin: 0;
  background: linear-gradient(to right, #667eea, #764ba2);
  color: #fff;
}

.container {
  text-align: center;
}

h1 {
  margin-bottom: 20px;
  font-size: 2.5rem;
}

#game-board {
  display: grid;
  grid-template-columns: repeat(3, 100px);
  grid-template-rows: repeat(3, 100px);
  gap: 10px;
  margin: 20px auto;
}

.cell {
  width: 100px;
  height: 100px;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 2rem;
  font-weight: bold;
  background-color: #fff;
  color: #333;
  border-radius: 8px;
  cursor: pointer;
  transition: background-color 0.3s, transform 0.3s;
}

.cell:hover {
  background-color: #f4f4f4;
  transform: scale(1.05);
}

.cell.taken {
  cursor: not-allowed;
}

#status {
  margin-top: 20px;
  font-size: 1.2rem;
  font-weight: bold;
}

.popup {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  display: flex;
  justify-content: center;
  align-items: center;
  background-color: rgba(0, 0, 0, 0.7);
}

.popup.hidden {
  display: none;
}

.popup-content {
  background-color: #fff;
  color: #333;
  padding: 20px;
  border-radius: 10px;
  text-align: center;
  box-shadow: 0 5px 15px rgba(0, 0, 0, 0.3);
}

#popup-message {
  margin-bottom: 20px;
  font-size: 1.5rem;
}

#popup-restart {
  padding: 10px 20px;
  font-size: 1rem;
  background-color: #007bff;
  color: #fff;
  border: none;
  cursor: pointer;
  border-radius: 5px;
}

#popup-restart:hover {
  background-color: #0056b3;
}

#game-mode {
  display: flex;
  justify-content: center;
  gap: 20px;
  margin-bottom: 30px;
}

button {
  padding: 10px 20px;
  font-size: 1rem;
  background-color: #007bff;
  color: #fff;
  border: none;
  cursor: pointer;
  border-radius: 5px;
}

button:hover {
  background-color: #0056b3;
}