style.css

html body {
  background-color: #f9fafb;
}

h1 {
  text-align: center;
}

.remain {
  font-size: 1.3em;
  font-weight: bold;
  padding-top: 10px;
}

#btn-container {
  text-align: center;
  justify-content: center;
  padding-bottom: 20px;
}

.gameCard {
  height: 100%;
  width: 100%;
  border: solid 1px black;
  text-align: center;
  border-radius: 10px;
  background-color: white;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
}

.unselected {
  cursor: pointer;
}

.setHint {
  outline: solid 5px blueviolet;
}

.selected-border {
  outline: solid 5px gold;
}

.bi {
  font-size: 50px;
  padding: 0.2em;
}

.red {
  color: red;
}

.blue {
  color: blue;
}

.green {
  color: green;
}

.white {
  color: white;
}

.col-3 {
  height: 120px;
}

@media only screen and (min-width: 765px) and (max-width: 991px) {
  .col-3 {
    height: 170px;
  }
}

@media only screen and (max-width: 765px) {
  .col-3 {
    height: 250px;
  }
}