* {
  box-sizing: border-box;
}

html, body {
  height: 100%;
  margin: 0;
}

body {
  font-family: "Times new roman";
}


header {
  background-color: #518F55;
  padding: 30px;
  color: white;
  font-size: 40px;
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
}

header img {
  position: absolute;
  width: 100px;
	left: 80px;
  height: auto;
}


.topnav {
  background-color: #83CC83;
}

.topnav ul {
  list-style: none;
  margin: 0;
  padding: 0;
  display: flex;
}

.topnav li {
  flex: 1;
  text-align: center;
}

.topnav a {
  display: block;
  padding: 15px 0;
  text-decoration: none;
  color: #2F3B2F;
  font-weight: bold;
  transition: 0.3s;
}

.topnav a:hover {
  background-color: #518F55;
  color: white;
}

.section {
	min-height: 80vh;
}

.sidenav {
  float: left;
  width: 20%;
  min-height: 100vh;
  background-color: #DDF3DD;
  padding: 20px;
}

.content {
  float: left;
  width: 80%;
  min-height: 100vh;
  padding: 30px;

  background-image:
    linear-gradient(rgba(255,255,255,0.7), rgba(255,255,255,0.7)),
    url("achtergrond.png");

  background-size: cover;
  background-position: center;
  background-attachment: fixed;
}
  
}

.sidenav ul {
  list-style: none;
  margin: 0;
  padding: 0;
}

.sidenav li {
  margin-bottom: 8px;
}

.sidenav a {
  display: block;
  padding: 10px;
  text-decoration: none;
  color: #2F3B2F;
  font-weight: bold;
  border-radius: 5px;
  transition: 0.3s;
  cursor: help;
}

.sidenav a:hover {
  background-color: #83CC83;
  color: white;
}



.sidenav a:hover {
  background-color: #83CC83;
  color: white;
}



.formula {
  max-width: 450px;
  margin-top: 20px;
}

.formula label {
  display: block;
  margin-top: 15px;
  margin-bottom: 5px;
  font-weight: bold;
}

.formula input {
  width: 100%;
  padding: 10px;
  border: 1px solid #bdbdbd;
  border-radius: 5px;
  font-size: 16px;
}

.formula button {
  margin-top: 20px;
  padding: 12px 20px;
  background-color: #518F55;
  color: white;
  border: none;
  border-radius: 5px;
  font-size: 16px;
  cursor: pointer;
}

.formula button:hover {
  background-color: #3f7143;
}

.abc {
  width: 250px;
  height: auto;
}

.output {
  margin-top: 25px;
  padding: 15px;
  background-color: #DDF3DD;
  border-left: 5px solid #518F55;
  min-height: 50px;
  white-space: pre-line;
}

.section::after {
  content: "";
  display: table;
  clear: both;
}