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

header {
  background-color: #4CAF50;
  color: white;
  padding: 1em;
  text-align: center;
}

nav ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
}

nav ul li {
  display: inline;
  margin: 0 1em;
}

section {
  padding: 2em;
}

footer {
  background-color: #4CAF50;
  color: white;
  text-align: center;
  padding: 1em;
  position: fixed;
  bottom: 0;
  width: 100%;
}

table {
  width: 100%;
  border-collapse: collapse;
}

table, th, td {
  border: 1px solid black;
}

th, td {
  padding: 10px;
  text-align: left;
}

.flashcard {
  width: 150px;
  height: 100px;
  border: 1px solid black;
  display: inline-block;
  margin: 10px;
  text-align: center;
  cursor: pointer;
  background-color: #f4f4f4;
  padding-top: 40px;
}