<div></div>

<a id="youtube" href="https://www.youtube.com/watch?v=oKXCmp1tGwY" target="_blank">
  See how this drawing was made
</a>

@import url('https://fonts.googleapis.com/css2?family=Share+Tech+Mono&display=swap');

html, body {
  overflow: hidden;
}

div {
  position: absolute;
  width: 100vw;
  height: 100vh;
  top: 0;
  left: 0;
  background: linear-gradient(to right, white 50%, black 0);
}

div::before,
div::after {
  content: "";
  display: block;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  background: #00f2;
  width: 70vmin;
  height: 70vmin;
  border-radius: 50%;
}

div::before {
  content: "Contrast";
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: 'Share Tech Mono', monospace, monospace;
  font-size: 13vmin;
  text-transform: uppercase;
  color: white;
  box-shadow: inset 0 0 0 2vmin white;
  background: black;
}

div::after {
  background: linear-gradient(to right, white 50%, black 0);
  mix-blend-mode: difference;
}