style.css

.grid {
  display:flex;
  flex-wrap: wrap;
  height: 458px; /*images plus padding*/
  width: 616px; /*images plus padding*/
  margin: auto;
}

.image {
  display: block;
  max-height: 150px;
  max-width: 150px;
  cursor: pointer;
  padding: 2px;
}

.image:active {
  transition: all 0.1s ease;
  transform: rotateY(180deg);
}

body {
  background-image: url("images/background.png");
  background-repeat: no-repeat;
  background-size: 100%;
  text-align: center;
  font-size: large;
}

#newGame {
  background-color:white;
  border-radius: 5px;
  padding: 10px 20px;
  font-size: large;
  margin: 10px;
  cursor: pointer;
  box-shadow: rgba(45, 35, 66, 0.4) 0 2px 4px,rgba(45, 35, 66, 0.3) 0 7px 13px -3px,#D6D6E7 0 -3px 0 inset;
}

#message {
  color: white;
  font-weight: normal;
}

footer {
  background-color: hsla(0, 0%, 100%, 0);
  width: 250px;
  color: blue;
  float: right;
}

#icon {
  visibility: hidden;
}

h3{
  margin: 10px;
}

p {
  margin: 5px;
}

button {
  margin: 5px;
}