style.css

body {
  background-color: gray;
}

.btn:hover {
  -webkit-box-shadow: 0px 0px 28px 0px rgba(255, 255, 255, 1);
    -moz-box-shadow: 0px 0px 28px 0px rgba(255, 255, 255, 1);
    box-shadow: 0px 0px 28px 0px rgba(255, 255, 255, 1);
}

.btn a {
  text-decoration: none;
}

a {
  text-decoration: none;
}

.bg-retro {
  background-image: url(https://images.unsplash.com/photo-1585881728919-5c0ce925ad10?ixlib=rb-1.2.1&ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&auto=format&fit=crop&w=2070&q=80);
}

.card {
  color: black;
}

.card{
  -webkit-filter: grayscale(100%);
  filter: grayscale(100%);
  margin-right: 5px;
  margin-bottom: 30px;
}

.card:hover {
  filter: none;
  -webkit-filter: grayscale(0);
  -webkit-box-shadow: 0px 10px 25px 14px rgba(0, 0, 0, 0.75);
    -moz-box-shadow: 0px 10px 25px 14px rgba(0, 0, 0, 0.75);
    box-shadow: 0px 10px 25px 14px rgba(0, 0, 0, 0.75);
}

.zoom {
  transition: transform 1s;
}

.zoom:hover {
  transform: scale(1.1);
}