* {
  box-sizing: border-box;
}

body {
  margin: 0;
      font-family: Arial, Helvetica, sans-serif;
}

.header {
  text-align: center;
  padding: 32px;
}

.row {
  display: -ms-flexbox; /* IE10 */
  display: flex;
  -ms-flex-wrap: wrap; /* IE10 */
  flex-wrap: wrap;
  padding: 0 4px;
}

/* Create four equal columns that sits next to each other */
.column {
  -ms-flex: 25%; /* IE10 */
  flex: 25%;
  max-width: 25%;
  padding: 0 4px;
}

.column img {
  margin-top: 8px;
  vertical-align: middle;
}

.column img:hover{
box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2), 0 6px 20px 0 rgba(0, 0, 0, 0.19);
    transition: 0.3s;
    opacity: 0.9;
}
/* Responsive layout - makes a two column-layout instead of four columns */
@media screen and (max-width: 800px) {
  .column {
    -ms-flex: 50%;
    flex: 50%;
    max-width: 50%;
  }
}

/* Responsive layout - makes the two columns stack on top of each other instead of next to each other */
@media screen and (max-width: 600px) {
  .column {
    -ms-flex: 100%;
    flex: 100%;
    max-width: 100%;
  }
}
/*nav bar*/
.navbar {
    width: 55px;
    background-color: #555;
    overflow: auto;
    position: absolute;
    z-index: 100;
    top: 50%;
    transform: translateY(-50%);
    position: fixed;
}

.navbar a {
    display: block;
    padding: 12px;
    color: white;
    text-decoration: none;
    font-size: 25px;
    width: 55px;
}

.navbar a:hover {
    background-color: darkred;
}

.active {
    background-color: darkred;
}
/* Style the buttons */
.btn {
  border: none;
  outline: none;
  padding: 10px 16px;
  background-color: #f1f1f1;
  cursor: pointer;
  font-size: 18px;
}

.btn:hover {
  background-color: #ddd;
}

.btn.active {
  background-color: #666;
  color: white;
}