body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen,
    Ubuntu, Cantarell, "Open Sans", "Helvetica Neue", sans-serif;
}

h1 {
  margin: 0;
  padding: 0;
}

.header {
  width: 100%;
  height: 100px;
  border-radius: 20px;
  background-color: red;
  text-align: center;
  color: white;
}

.body-section {
  display: flex;
  margin: 10px 10px;
}

.sidebar {
  width: 15%;
  height: 530px;
  border-radius: 20px;
  background-color: green;
  text-align: center;
  color: white;
}

.s2 {
  background-color: hotpink;
}

.main-body {
  width: 68%;
  height: 530px;
  border-radius: 20px;
  background-color: yellow;
  text-align: center;
  margin: 0 10px 0 10px;
}

.footer {
  width: 100%;
  height: 80px;
  border-radius: 20px;
  background-color: blue;
  text-align: center;
  color: white;
}

@media (max-width: 770px) {
  .body-section {
    display: block;
  }
  .main-body {
    width: 100%;
    height: 340px;
    margin: 10px 0 10px 0;
  }
  .sidebar {
    width: 100%;
    height: 70px;
    text-align: center;
  }
}