* {
  box-sizing: border-box;
}

ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  overflow: hidden;
  border: 1px solid #e7e7e7;
  background-color: #f3f3f3;
}

li {
  float: center;
}

li a {
  display: block;
  color: #666;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
}

li a:hover:not(.active) {
  background-color: #ddd;
}

li a.active {
  color: white;
  background-color: #04AA6D;
}


.header {
  text-align: center;
  padding: 12px;
}


.footer {
  text-align: center;
  width: 100%;
}

.column {
  float: left;
  width: 33.33%;
  padding: 5px;
}

/* Clearfix (clear floats) */
.row::after {
  content: "";
  clear: both;
  display: table;
}

.gallery {
  margin: auto;
}

.gallery img{
 transition: 1s;
 padding: 15px;
 width: 300px; 
}


.gallery img:hover{
 filter: grayscale(100%);
 transform: scale(1.1);
}