main {
  display: flex;
  justify-content: center;
  padding: 0 200px; /* 左右100pxの余白 */
}

main > div {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 20px; /* 画像間の上下20px */
  width: 100%;
  padding: 20px 0; /* 上下の余白 */
}

main img {
  max-width: 100%;
  height: auto;
  display: block;
}