<div class="square red" data-scale="1">scaleX(1)</div>
<div class="square red" data-scale="0.5">scaleX(0.5)</div>
<div class="square red" data-scale="-0.5">scaleX(-0.5)</div>
<div class="square red" data-scale="-1">scaleX(-1)</div>

body {
  display: flex;
  align-items: center;
  justify-content: center;

  height: 100vh;
  margin: 0;
  overflow: hidden;

  font-family: sans-serif;
}

.square {
  box-sizing: border-box;
  width: 200px;
  height: 200px;
  margin-right: 20px;
  padding-top: 20px;

  color: #fff;
  font-size: 1.5em;
  text-align: center;

  background: #03a9f4;
}

[data-scale="1"] {
  transform: scaleX(1);
}

[data-scale="0.5"] {
  transform: scaleX(0.5);
}


[data-scale="-0.5"] {
  transform: scaleX(-0.5);
}

[data-scale="-1"] {
  transform: scaleX(-1);
}

.red {
  background: #ef5350;
}

.green {
  background: #66bb6a;
}

.blue {
  background: #42a5f5;
}