style.css

body {
  background-color: #222;
  color: #fff;
  font: 14px Verdana;
}

table {
  width: 100%;
}

input {
  width: 100%;
  padding: 5px;
}

#top tr td:first-child {
  width: 260px;
  font-size: 2em;
  padding-left: 25px;
  position: relative;
}

#title {
  font-weight: bold;
}

#title span {
  color: #4dd2ff;
}

#help {
  font-size: 0.4em;
  color: #eee;
  text-decoration: none;
  width: 50px;
  display: inline-block;
  position: absolute;
  top: 10px;
  right: 2%;
}

#help::after {
  content: "❔";
}

#help:hover::after {
  content: "❗";
  color: red;
}

td {
  padding: 5px 10px;
}

html, body, .container {
  height: 100%;
}

.container {
  display: flex;
  flex-direction: column;
  flex-wrap: nowrap;
  justify-content: flex-start;
  align-content: stretch;
  align-items: stretch;
}

.item:nth-child(1) {
  order: 0;
  flex: 0 1 auto;
  align-self: auto;
}

.item:nth-child(2) {
  order: 1;
  flex: 1 0 auto;
  align-self: auto;

  position: relative;
}

iframe {
  position: absolute;
  width: 100%;
  height: 100%;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
}