* {
    box-sizing: border-box;
}

body {
  margin: 0; 
}

/* Style the header */
header {
  background-color: #f1f1f1;
  padding: 5px;
}

/* Style the top navigation bar */
  .topnav {
    overflow: hidden;
    background-color: #333;
  }

  /* Style the topnav links */
  .topnav a {
    float: left;
    display: block;
    color: #f2f2f2;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
  }

/* Change color on hover */
.topnav a:hover {
  background-color: #ddd;
  color: black;
}

/* Create three equal columns that floats next to each other */
.column {
  float: left;
  width: 33.33%;
  padding: 15px;
}

/* Clear floats after the columns */
.row:after {
  content: "";
  display: table;
  clear: both;
}

img {
  max-width: 100%;
  height: auto;
}

/* Responsive layout - makes the three columns stack on top of each other instead of next to each other */
@media screen and (max-width:600px) {
  .column {
    width: 100%;
  }
}