JSFiddle - React, Tailwind, and code Playground

HTML

<div class="is-vertical-center">
  <div class="box">
      <div class="text-center">
        <img class="img-on-top" src="assets/logo.png">
      </div>
      <div class="router-outlet">
        <div class="pure-g">
          <div class="pure-u-1-1">
              <h5>Start</h5>
          </div>
        </div>
        <div class="pure-g">
          <div class="pure-u-1-1">
              <p>
                 Welcome Lorem ipsum
              </p>
          </div>
        </div>
      </div>
  </div>
</div>

CSS

.is-vertical-center {
  height: 100%;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
}

.box {
  background-color: $color-ts-main-flat;
  border: 1px solid $color-ts-main-border;
  border-radius: 4px;
  max-width: 30%;
  padding: 20px;
}

.text-center {
  text-align: center !important;
}

.img-on-top {
  top:0;
  margin-top:5%;
  position:absolute;
  right: 50%;
}

.router-outlet {
  flex: 1 0 100px;
  background-color:blue;

  /* stretch element immediately following the router-outlet element within the same parent element.
   * This is the element injected by angular (Assumption)
   */
  router-outlet + * {
    height: 100%;
    width: 100%;
  }
}