style.css

body {
    text-align: center;
    font-family: Arial, Helvetica, sans-serif;
    height: 95vh;
}

.game-title {
    font-size: 50px;
    font-weight: bold;
}

.game-board {
    display: inline-grid;
    grid-template-columns: auto auto auto;
    background-color: grey;
    padding: 10px;
}

.cell {
    background-color: white;
    border: 1px solid black;
    padding: 30px;
    font-size: 70px;
    text-align: center;
    height: 100px;
    width: 100px;
    cursor: pointer;
}

.game-info {
    font-size: 30px;
    font-weight: bold;
}

.game-info-button {
  background-color: transparent;
  border: 2px solid black;
  border-radius: 16px;
  padding: 8px 16px;
  cursor: pointer;
  font-size: 20px;
  font-weight: bold;
}

.green {
    background-color: green;
}

.popup {
  /* center the popup in the middle of the page*/
  position: fixed;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  /* style the popup */
  background-color: grey;
  border: 1px solid black;
  border-radius: 16px;
  padding: 16px;
  width: 300px;
  height: 200px;
  text-align: center;
}

.popup-title {
  font-size: 30px;
  font-weight: bold;
}

.popup-button {
  background-color: white;
  border: 2px solid black;
  border-radius: 16px;
  padding: 8px 16px;
  cursor: pointer;
  font-size: 20px;
  font-weight: bold;
  margin: 0 auto;
}