* {
  margin: 0;
  padding: 0;
}
body {
  background: linear-gradient(180deg, #ffe000 0%, #ffd200 50%, #f5c400 100%);
}

.mainSection {
  position: relative;
  text-align: center;
}

.mainSection img {
  max-width: 100%;
  height: auto;
}