JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
<html lang="en" dir="ltr">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link href="https://fonts.googleapis.com/css?family=IBM+Plex+Mono:400,400i|IBM+Plex+Sans:100,100i,400,400i,700,700i" rel="stylesheet">
    <title>Portfolio</title>
  </head>
  <body>
    <!-- Full page intro -->
    <div class="front-page full-page">
      <span id="title-text" class="center head-text">Hi</span>
      </div>
    </div>
  </body>
</html>

CSS

:root {
  --txt-color: #fff;
  --txt-box-bg: #424242;
  --main-bg: #000;
  --transparent: transparent;

  /* front page title text */
  --main-front-color: #e84118;
  --second-front-color: #fbc531;
  --third-front-color: #00a8ff;
}

* {
  margin: 0px;
  padding: 0px;
}
/* Text */
.head-text {
  font-family: "IBM Plex Sans", sans-serif;
  color: var(--txt-color);
}

.main-text {
  font-family: "IBM Plex Mono" monospace;
  color: var(--txt-color);
}

.bold {
  font-weight: bold;
}

.normal {
  font-weight: normal;
}

.light {
  font-weight: lighter;
}

/* Allgin */
.center {
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

/* classes */
.front-page {
  background-color: var(--main-bg);
}

.full-page {
  background-size: cover;
  height: 100vh;
}

/* IDs */
#title-text {
  position: absolute;
  display: inline-block;

  background-clip: text;
  color: transparent;
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  white-space: nowrap;


  background-image: linear-gradient(#000,#000);
  background-size: 100% 100%;
  background-position: right;
  background-repeat: no-repeat;

  transition: 1s all;
  font-weight: bold;
  text-align: center;
  font-size: 90px;
  -webkit-text-stroke: 2px var(--main-front-color);
  animation: stroke-rainbow 13s linear infinite;
  z-index: 2;
}

#title-text::after {
  content: '';
  display: block;
  width: 0;
  height: 4px;
  background: var(--txt-color);
  transition: 1s all;
  animation: stroke-rainbow 13s linear infinite;
}

#title-text:hover {
  background-size: 0% 100%;
}

#title-text:hover::after {
  width: 100%;
}

@keyframes stroke-rainbow {
  0% {
    border-color: var(--main-front-color);
    -webkit-text-stroke-color: var(--main-front-color);
    background-color: var(--main-front-color);
    #title-text::after {

    }
  }
  25% {
    border-color: var(--second-front-color);
    -webkit-text-stroke-color: var(--second-front-color);
    background-color: var(--second-front-color);
  }
 ...