* {
    padding: 0;
    margin: 0;
    box-sizing: border-box;
}

html,body {
    font-family: sans-serif;
    font-size: 18px;
    -webkit-font-smoothing: antialiased;
    background-color: rgb(36, 36, 36);
    height: 100vh;
}

header {
  background: rgb(0, 47, 101);
  color: #fff;
}

header h1, header p {
  text-align: center;
  padding: 4px 4px;
}

main {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    height: 70vh;
}

footer {
  display: flex;
  align-items: center;
  justify-content: center;
  background-color: #908f8f;
  height: 6vh;
}

footer p {
  padding-bottom: 6px;
}

.image-set-selector {
  display: flex;
  flex-direction: row;
  justify-content: space-evenly;
}

.image-set-selector .image-thumbnail {
  width: 100px;
  height: 100px;
  margin: 10px;
  border: 4px solid #00000000;
}


.image-set-selector .image-thumbnail:hover {
  cursor: pointer;
  border: 4px solid #fff;
}

.image-set-selector .image-thumbnail img {
  width: 100%;
  height: 100%;
}

.spacer {
  height: 100px;
}

  .image-container img {
    position: absolute;
    top: 0;
    left: 0;
    opacity: 0;
    transition: opacity 1s ease;
  }
  
  .image-container img:first-child {
    opacity: 1;
  }
  
@media (max-width: 940px)  {
  .image-set-selector {
    flex-wrap: wrap;
  } 
}

@media (max-width: 650px)  {
  .image-set-selector {
    flex-wrap: wrap;
  } 
}

@media (max-width: 400px)  {
  header {
    width: 100%;
  }
}