<h1>Hover Me</h1>

h1 {
  --s: 0.1em;   /* the thickness of the line */
  --c: #2c4bff; /* the color */
  
  color: #0000;
  padding-bottom: var(--s);
  background: 
    linear-gradient(90deg,var(--c) 50%,#000 0) calc(100% - var(--_p,0%))/200% 100%,
    linear-gradient(var(--c) 0 0) 0% 100%/var(--_p,0%) var(--s) no-repeat;
  -webkit-background-clip: text,padding-box;
          background-clip: text,padding-box;
  transition: 0.5s;
}
h1:hover {--_p: 100%}


body {
  height: 100vh;
  margin: 0;
  display: grid;
  place-content: center;
}
h1 {
  font-family: system-ui, sans-serif;
  font-size: 5rem;
  cursor: pointer;
}