style.css

html, body {
  height: 100%;
  width: 100%;
  overflow-x: clip;
/*   overflow-y: initial !important; */
/*   overflow-x: hidden initial; */
/*   overflow-y: initial !important; */
}

h1, h6 {
  text-align: center;
}

h1 {
  font-size: 3.5em;
}

h6 {
  font-weight: normal;
  font-size: 1.5em;
}

a {
  color: red;
}

a:link {
  color: red;
  text-decoration: none;
}

a:hover {
  color: red;
  text-decoration: underline;
}

#number {
  margin: auto;
  display: block;
  width: 90%;
  height: 2em;
  resize: none;
  font-size: 4em;
  border: 5px solid red;
  border-radius: 20px;
  box-sizing: border-box;
  padding: 15px;
  text-align: center;
  font-family: 'Roboto Slab', serif;
}

#output {
  font-size: 2em;
  text-align: center;
/*   font-weight: bolder; */
  font-family: 'Poppins', sans-serif;
  margin: 2%;
}

.result {
  font-size: 0.8em;
  overflow-wrap: break-word;
  font-weight: bolder;
}

hr {
  margin: 2% 0;
}