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

#content {
  position: relative;
  width: 100%;
  height: calc(100% - 50px);
  overflow-y: auto;
}

.page {
  display: none;
  padding: 20px;
  text-align: center;
}

.page.active {
  display: block;
}

#navbar {
  position: fixed;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 50px;
  background-color: #f1f1f1;
  display: flex;
  justify-content: space-around;
  align-items: center;
}

#navbar button {
  background-color: transparent;
  border: none;
  font-size: 16px;
  cursor: pointer;
}