* {
  box-sizing: border-box;
}

/* Style the body */
body {
  font-family: Arial, Helvetica, sans-serif;
  margin: 0;
  background-color: #F9E8C0;
}

/* Header/logo Title */
.header {
  padding: 80px;
  text-align: center;
  background-image: url("air_pollution.jpg")
}

/* Increase the font size of the heading */
.header h1 {
  font-size: 40px;
}

/* Sticky navbar - toggles between relative and fixed, depending on the scroll position. It is positioned relative until a given offset position is met in the viewport - then it "sticks" in place (like position:fixed). The sticky value is not supported in IE or Edge 15 and earlier versions. However, for these versions the navbar will inherit default position */
.navbar {
  overflow: hidden;
  background-color: #2A1E0D;
  position: sticky;
  position: -webkit-sticky;
  top: 0;
}

/* Style the navigation bar links */
.navbar a {
  float: left;
  display: block;
  color: white;
  text-align: center;
  padding: 14px 20px;
  text-decoration: none;
}


/* Right-aligned link */
.navbar a.right {
  float: right;
}

/* Change color on hover */
.navbar a:hover {
  background-color: #AD7751;
  color: black;
}

/* Active/current link */
.navbar a.active {
  background-color: #7B3D11;
  color: white;
}

/* Main Page */
.main {   
  -ms-flex: 70%; /* IE10 */
  flex: 70%;
  padding: 30px;
  max-width: 1000px;
  margin: 0 auto;
  float: none;
  text-align: justify;

/* Responsive layout - when the screen is less than 700px wide, make the two columns stack on top of each other instead of next to each other */
@media screen and (max-width: 700px) {
  .row {   
    flex-direction: column;
  }
}

/* Responsive layout - when the screen is less than 400px wide, make the navigation links stack on top of each other instead of next to each other */
@media screen and (max-width: 400px) {
  .navbar a {
    float: none;
    width: 100%;
  }
}