Style.css

* {
  box-sizing: border-box;
}

body {
  background-color: #ffffff;
}

.container {
  display: flex;
  flex-direction: column;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
}

/* Banner Image CSS */
.header-img {
  padding: 0;
  height: 200px;
  margin: 50px auto;
}

/* Grid CSS */

.grid-container{
  display: grid;
  grid-template-columns: 280px 280px 280px;
  justify-items: center;
  grid-row-gap: 18px;
  grid-column-gap: 18px;
}

/* Image CSS */
.img-f {
  border-radius: 15px;
  cursor: pointer;
  transition: 0.3s;
  width: 100%;
  height: 100%;
  -webkit-user-select: none; /* Chrome/Safari */
  -moz-user-select: none; /* Firefox */
  -ms-user-select: none; /* IE10+ */
}

.img-f:hover {
  opacity: 0.7;
}

/* The Modal (background) */
.modal {
  display: none; /* Hidden by default */
  position: fixed; /* Stay in place */
  z-index: 1; /* Sit on top */
  padding-top: 100px; /* Location of the box */
  left: 0;
  top: 0;
  width: 100%; /* Full width */
  height: 100%; /* Full height */
  overflow: auto; /* Enable scroll if needed */
  background-color: rgb(0, 0, 0); /* Fallback color */
  background-color: rgba(0, 0, 0, 0.9); /* Black w/ opacity */
}

/* The footer*/
.footer {
  padding: 15px;
  color: #222;
  background-color: #f5f5f5;
  margin-top: 100px;
  text-align: center;
}

/* Modal Content (image) */
.modal-content {
  margin: auto;
  display: block;
  width: 540px;
  max-width: 677px;
  height: 540px;
  -webkit-user-select: none; /* Chrome/Safari */
  -moz-user-select: none; /* Firefox */
  -ms-user-select: none; /* IE10+ */
}

/* Caption of Modal Image */
#caption {
  margin: auto;
  display: block;
  width: 80%;
  max-width: 700px;
  text-align: center;
  color: #ccc;
  padding: 10px 0;
  height: 150px;
}

/* Add Animation */
.modal-content,
#caption {
  -webkit-animation-name: zoom;
  -webkit-animation-duration: 0.6s;
  animation-name: zoom;
  animation-duration: 0.6s;
}

@-webkit-keyframes zoom {
  from {
    -webkit-transform: scale(0);
  }
  to {
    -webkit-transform: scale(1);
  }
}

@keyframes zoom {
  from {
    transform: scale(0);
  }
  to {
    transform: scale(1);
  }
}

/* The Close Button */
.close {
  position: absolute;
  top: 15px;
  right: 35px;
  color: #f1f1f1;
  font-size: 40px;
  font-weight: bold;
  transition: 0.3s;
}

.close:hover,
.close:focus {
  color: #bbb;
  text-decoration: none;
  cursor: pointer;
}

/* 100% Image Width on Smaller Screens */
@media only screen and (max-width: 700px) {
  .header-img {
    padding: 0;
    height: 100px;
    margin: 50px auto;
    display: block;
  }
  
  .grid-container{
    display: grid;
    grid-template-columns: 150px 150px;
  }

  .last{
    grid-column: 1/-1;
    width: 150px;
  }

  .modal-content {
    margin: 16vh auto;
    display: block;
    width: 250px;
    height: 250px;
    
    -webkit-user-select: none; /* Chrome/Safari */
    -moz-user-select: none; /* Firefox */
    -ms-user-select: none; /* IE10+ */
  }
  
}

@media screen and (min-width: 710px) and (max-width:800px) {
  .grid-container{
    display: grid;
    grid-template-columns: 200px 200px 200px;
  }
}