JSFiddle - React, Tailwind, and code Playground

HTML

<div class="maincontainer">
  <div id="block1" class="blocks">
  </div>
  <div id="block2" class="blocks">
  </div>
</div>

CSS

.maincontainer {
  display: block;
  background-color: black;
  margin: 0 auto;
  width: 100%;
  min-width: 600px;
  height: 250px;
}
body {
  background-color: white;
}
.blocks {
  background-color: red;
  position: absolute;
  display: inline-block;
  width: 100px;
  height: 50px;
}
#block1 {
  background-color: green;
  top: 100px;
  left: 0;
  right: 0;
  bottom: 0;
  margin-left: auto;
  margin-right: auto;
}
#block2 {
  top: 100px;
  left: 0;
  right: 25%;
  bottom: 0;
  margin-left: auto;
  margin-right: auto;
}