mobile.html

<style media="screen">
  p {
  text-align: center;
  font-size: 50px;
}

  .flex-container {
  display: flex;
  flex-direction: column;
  flex-wrap: nowrap;
  justify-content: center;
  align-items: center;
  align-content: normal;
  height: 100%;
}

.flex-items:nth-child(1) {
  display: block;
  flex-grow: 0;
  flex-shrink: 1;
  flex-basis: auto;
  align-self: auto;
  order: 0;
}

.flex-items:nth-child(2) {
  display: block;
  flex-grow: 0;
  flex-shrink: 1;
  flex-basis: auto;
  align-self: auto;
  order: 0;
}
</style>

<div class="flex-container">
   <div class="flex-items">
     <p>Please use desktop</p>
   </div>
   <div class="flex-items">
     <img src="assets/laptop.png" alt="" width="200">
   </div>
</div>