style.css

html {
  height: 100%;
}
body {
  height: -webkit-calc(100% - 2em);
  height: calc(100% - 2em);
  font-family: 'Roboto', sans-serif;
  background-color: LightSlateGray;
  color: Gainsboro;
}
form {
  text-align: center;
  width: 100%;
  height: -webkit-calc(100% - 5em);
  height: calc(100% - 5em);
}
#textbox {
  height: -webkit-calc(100% - 5em);
  height: calc(100% - 5em);
  width: -webkit-calc(100% - 5em);
  width: calc(100% - 5em);
  max-width: 90%;
  margin-bottom: 1.5em;
  line-height: 1.3em;
  padding: 0.5em;
  border: 2px solid #abc;
  border-radius: 10px;
  box-shadow: 0 0 5px 1px inset;
  outline: none;
}
a#footer {
  font-size: small;
  position: fixed;
  bottom: 0;
  right: 0;
  padding: 0.2em 0.7em;
  border-top-right-radius: 1em;
  background-color: white;
  box-shadow: -1px -1px 5px 3px rgba(0, 0, 0, 0.3);
  transform: rotate(-90deg) translateX(100%);
  transform-origin: right bottom;
  -webkit-transform: rotate(-90deg) translateX(100%);
  -webkit-transform-origin: right bottom;
  text-decoration: none;
  color: grey;
}
p {
  padding: 0 1em;
}
a {
  color: gold;
}